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A case study of measles vaccination for university students during the measles outbreak in Tokyo, Japan, 2007
J Infect Chemother (2012) 18:341–346 DOI 10.1007/s10156-011-0343-x
ORIGINAL ARTICLE
A case study of measles vaccination for university students during the measles outbreak in Tokyo, Japan, 2007 Ryuichi Fujisaki • Mariko Yamamura • Shigeru Abe • Kousuke Shimogawara • Michihiro Kasahara • Hajime Nishiya • Miho Makimura • Koichi Makimura
Received: 16 December 2010 / Accepted: 25 October 2011 / Published online: 3 December 2011 Ó Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases 2011
Abstract In April 2007, seven students belonging to the same class at Teikyo University developed measles. To prevent the spread of infection, 27 of 106 students in the same class who had low anti-measles antibody titers as measured by hemagglutination inhibition (HI) assay were vaccinated. After the outbreak had subsided, the HI values were investigated in 103 students, and they answered questionnaires about their health condition during the period of the outbreak and their previous clinical histories of measles, including vaccination records. There was no R. Fujisaki Emergency Room of Teikyo University Hospital, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan M. Yamamura Department of Internal Medicine, Faculty of Medicine, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan S. Abe M. Makimura K. Makimura (&) Teikyo University Institute of Medical Mycology, Teikyo University, 356 Otsuka, Hachioji, Tokyo 192-0395, Japan e-mail: [email protected] K. Shimogawara Laboratory of Chemistry, Faculty of Medicine, Teikyo University, 356 Otsuka, Hachioji, Tokyo 192-0395, Japan M. Kasahara Laboratory of Biophysics, Faculty of Medicine, Teikyo University, 356 Otsuka, Hachioji, Tokyo 192-0395, Japan H. Nishiya School of Medical Technology, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan K. Makimura Laboratory of Space and Environmental Medicine, Graduate School of Medicine, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan
new case of measles after introduction of the vaccination program. However, the HI titers of 42% of the students who were not vaccinated in this program were significantly elevated. Fever and catarrhal signs occurred in 7 of these students with pre-exposure titers of 8 or less. The postexposure HI titers of 71% of students who were unaffected by measles and had high HI titers ([8) before the epidemic did not increase. These results suggested that people with low HI titers may become potential carriers of measles and that measurement of pre-exposure HI anti-measles antibody titer is a useful method for selection of candidates to undergo vaccination. Keywords Measles Vaccination Outbreak Student Hemagglutination inhibition (HI) Enzyme immunoassay (EIA)
Introduction Measles virus causes acute infectious disease in humans [1, 2] and is the etiological agent one of the most important lethal infections in young children. Measles infection shows several clinical signs, i.e., cough, coryza, high fever, maculopapular rash, conjunctivitis, and complications of pneumonia and/or encephalitis in some cases, which occasionally results in death. In 2001, there was a nationwide outbreak of measles in Japan. Most patients affected in this outbreak were infants and young children [3]. Following this measles outbreak, the government of Japan strengthened the measles surveillance system in each prefecture and promoted a nationwide campaign of vaccination for children. These attempts resulted in a marked reduction in the measles infection rate among younger people. However, in 2006 a small local prevalence of
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measles led to an outbreak in Japan that lasted until the summer of 2007 [3]. The outbreak in 2007 was different from previous outbreaks in that the majority of patients were young adults or adolescents attending high schools and university students [3–7]. Measles vaccination in Japan started in 1978. The majority of people born before 1978 had no history of measles vaccination, but their antibody titers against measles are sufficiently high to avoid infection, which can be explained by natural sensitization to measles. Younger generations show reduced levels of antibodies against measles [3, 4], which is considered to be caused by the decrease in the opportunity for natural sensitization and lack of complete vaccination. From 2006, two dosage schedules were started, at 1 year and at 5–6 years of age, but this system could not prevent the measles outbreak in summer of 2007. The Japanese government implemented a 5-year vaccination catch-up campaign for cohorts aged 13 and 18 years to prevent future outbreaks of measles [3] from 2008. However, complete vaccination in this generation seems not to be actually possible for social and economic reasons. In addition, some persons avoid vaccination because of highly publicized problems with measles, mumps, and rubella (MMR) vaccine between 1989 and 1993 in Japan [8]. Practically, it is necessary to present reasonable criteria of vaccination. In this study, we used the hemagglutination inhibition (HI) test for measurement of antibody activity against measles. The HI test is generally less sensitive than enzyme immunoassay (EIA) [9]. However, HI is a simpler and lower-cost method than EIA. In addition, the HI test does not require specialized instruments or techniques and can therefore be introduced conveniently into small laboratories. Here, we investigated pre- and post-HI titers of 103 students exposed to a measles outbreak. The clinical condition and previous history of measles and vaccine records of all subjects were also investigated.
Materials and methods
J Infect Chemother (2012) 18:341–346
departments by their special lecture schedule. They also lived within a very limited area around the university. Study population A total of 103 of the 106 students provided informed consent to participation in this study. The average age of subjects was 22 years old. These 103 subjects included 7 students who developed measles. Titration of antibodies against measles by HI test and EIA (serological tests) The anti-measles antibody titers of the first-grade medical school students were measured by hemagglutination inhibition (HI) test [7] before the beginning of their first school session (10 April 2007). These results were used as the preexposure titers. HI tests performed using commercial kits obtained from SRL (Tokyo, Japan) involved measuring HI titers by testing endpoint serial dilution of blood samples for hemagglutination inhibition. In this study, an increase in post-exposure HI titers of more than fourfold compared to the pre-exposure value was determined to be significant. Post-exposure blood samples were obtained on June 11, when we confirmed the end of the measles epidemic at this university because no new patient had been observed for 1 month. The blood samples of 103 subjects were investigated as post-exposure titers by HI test and EIA (SRL). Clinical condition and vaccination history Information from participants concerning symptoms experienced during the outbreak was obtained by selfadministered questionnaires. Signs and symptoms elicited on the questionnaire included fever and catarrhal symptoms (cough, runny nose, red watery eyes or light sensitivity, sore throat), headache, and diarrhea. Information about previous and recent vaccinations and measles history were obtained from students, parents, and provider-verified birth records.
Background Vaccination During the period from March to May 2007, 7 students in the first grade of the Faculty of Medicine on Teikyo University Hachioji campus developed measles. A total of 106 students belonged to the same class. The first case was observed in March, and the last case was detected on April 29. The university is located in the eastern part of Tokyo; the students of the medical school all belonged to the same class and were isolated from other students from different
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There was a serious shortage of measles vaccine in Japan in spring 2007. Some students who wished to receive the vaccination could not do so because of insufficient availability of the vaccine. The 27 subjects with low HI titers (\8) and 5 with HI titers C8 who strongly desired vaccination had the vaccination between April 21 and June 3; a total of 32 subjects were vaccinated (one time/person).
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Results Measles patients (cases) The data for seven students diagnosed with measles during the period between March and May 2007 are shown in Table 1. One student (case 6) developed measles illness between March 26 and April 7 and was considered to have recovered from the illness before collection of the pre-exposure blood sample (Table 1). Case 1 showed mild clinical signs of measles at pre-exposure blood sample collection and may have been in the very early stages of infection at this point. Pre-exposure samples from all cases had low titers (\8) of HI, except for case 6, who had recently recovered from measles. The post-exposure titers of six students diagnosed with measles (all positive cases except case 6) significantly increased (4- to 128-fold higher than pre-exposure titers). The clinical manifestations in these cases were all consistent with classical measles symptoms, i.e., fever, confluent maculopapular rash, and cough, coryza, or conjunctivitis. Pre-exposure HI titers: comparison between cases and non-cases Six of the seven students affected with measles after preexposure sampling had the lowest HI titers (\8). Subjects who did not have clinical measles had antibody titers ranging from\8 to 256 (data not shown). Fifty-seven of 96 students had HI titers B8 (59%). Thirty-nine students (41%) had HI titers [16 [HI titer: 256 (n = 1), 128 (n = 6), 64 (n = 1), 32 (n = 11), 16 (n = 20) (data not shown)]. The average HI titers in cases and non-cases were 8 and 23, respectively.
(75%) showed increases in HI titer of more than fourfold compared to the pre-exposure value. None of the subjects with pre-exposure titers [8 showed an increase in postexposure titer. In the non-vaccinated group (64 students), 27 subjects (42%) showed increases in HI titer of more than fourfold compared to the pre-exposure value. Nonvaccinated subjects with pre-exposure titers of 8 or less included 7 who showed both fever and catarrhal signs (Table 2). Only 1 non-vaccinated student with a titer \8 showed fever (Table 2). Comparison of the results of HI test with those of EIA We compared the results of HI test and those of EIA using all post-exposure blood samples (Fig. 1). The HI titers of subjects were closely correlated to the values determined by EIA. Table 2 cases
Change of hemagglutination inhibition (HI) titer in non-
Non-case (n = 96)
C4 fold
\4 fold
Vaccinated (n = 32) Pre titer \8
22 (7/2)a
Pre titer = 8
2 (0/0)
Pre titer [8 Non-vaccinated (n = 64)
a
0
5 (1/0) 0 3 (0/0)
Pre titer \8
2 (2/2)
1 (0/0)
Pre titer = 8
14 (5/5)
11 (1/0)
Pre titer [8
11 (1/0)
25 (5/1)
Clinical signs: catarrh/fever
Pre titer, pre-exposure titer
Pre- and post-exposure HI titers: non-cases The increase in HI titer of non-cases was investigated (Table 2). In the vaccine group (32 students), 24 subjects
Table 1 Hemagglutination inhibition (HI) titer and clinical information of cases Case
Pre titer
Post titer
Previous measles
Previous vaccinations
Measles illness
1
\8
256
–
Unknown
2
\8
1,024
–
0
April 25–May 5
3 4
\8 \8
1,024 32
– –
Unknown 0
April 25–April 30 April 22–April 28
5
\8
512
–
Unknown
6
32
64
–
0
7
\8
1,024
–
1
April 7–April 14
April 22–May 2 March 26–April 7 April 23–April 28
Pre titer, pre-exposure titer; Post titer, post-exposure titer
Fig. 1 Comparison of titers determined by hemagglutination inhibition (HI) and enzyme immunoassay (EIA). The HI and EIA titers of 103 individuals are expressed as small points (small filled circles). Average values are expressed as large symbols (large filled circles). Standard differences are indicated by vertical bars
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J Infect Chemother (2012) 18:341–346
Table 3 Previous measles and vaccination history of cases and non-cases Case of measles
Pre titer
Post titer
\8
=8
[8
\4-fold
Clinical signs C4-fold
Previous measles (n = 11)
0
4
1
6
5
6
2
Previous vaccine, 0 (n = 10)
3
3
0
7
4
6
3
Previous vaccine, 1 (n = 54)
1
18
18
18
22
32
18
Previous vaccine, 2 (n = 9)
0
5
2
2
4
5
2
Unknown (n = 30)
3
10
8
12
15
15
4
Clinical signs: catarrh and/or fever Pre titer, pre-exposure titer; Post titer, post-exposure titer
Relationships between previous vaccinations and history of measles and resistance to infection In this study, the students who had histories of measles infection and with records of vaccination with two doses did not develop typical measles illness (Table 3). However, history of measles and number of previous vaccinations were not related to pre- or post-exposure HI titers in either cases or non-cases.
Discussion Sporadic outbreaks of measles occurred in Japan from 2006 to 2007 [3–7]. In many cases, outbreaks were reported from distinct capitals, and occurred in schools with students aged 10–20 years old. There have been several reports regarding phylogenetic analysis of measles virus [5–7]. However, there have been few reports of pre- and post-exposure anti-measles antibody levels. Chen et al. [10] reported a large-scale measles epidemic in the dormitories of Boston University (USA). They investigated pre- and post-exposure blood samples and reported changes in specific anti-measles antibody using EIA and the plaque reduction neutralization (PRN) test. In this study, we collected serological and clinical information for 103 students exposed to measles and investigated the effects of vaccination in students with low levels of anti-measles antibody to establish a concrete strategy for preventing the expansion of measles outbreaks. Significance of pre-exposure HI titer The presence of detectable measles antibody has been thought to indicate that an individual would be protected against falling ill if exposed to the measles virus. However, there have been only a few reports regarding pre-exposure anti-measles antibody titer [10, 11]. In this study, we used the HI test for measurement of anti-measles antibody titers. The standard HI test, a
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traditional assay, is less sensitive than EIA and the PRN assay [9, 12, 13]. However, the HI test can be performed easily and does not require special techniques or expensive equipment. Thus, we gave priority to the convenience, rapidity, and practical applicability of the HI test. The results of the present study using the HI test suggested that a titer [8 was required for protection against measles. All patients in this study had HI pre-exposure titers \8, with the exception of case 6 who had recently recovered from illness before pre-exposure sampling. The 30 subjects who had low pre-exposure titers (\8) did not develop measles (Table 2). Using the PRN assay, Chen et al. [10] suggested that a titer [120 mIU/ml was required for protection against falling ill with measles. The number of patients in our study was too small to determine the border value; however, at least the subjects whose pre-exposure HI titer was \8 were susceptible to measles infection. Post-exposure HI titers From the point of view of post-exposure titer change, the 103 students were divided into three groups: group 1 consisted of 7 cases of measles; group 2 consisted of 51 non-cases whose post-HI titers increased by more than fourfold; and group 3 consisted of 45 non-cases whose post HI titers did not increase. The subjects in group 2 had preexposure HI titers \8 (47%), 8 (31%), and [8 (22%). On the other hand, 13%, 24%, and 62% of subjects in group 3 had pre-exposure HI titers \8, 8, and [8, respectively. Group 2 included 9 subjects who showed fever and catarrhal signs during the epidemic period; group 3 included only 1 of these subjects. Comparison of the results suggested that the students in group 2 responded to vaccination and/or measles virus, and the subjects with low pre-exposure titers (B8) were more affected by the measles than those with high pre-exposure titers ([8). Interestingly, the questionnaires regarding the relationships between students revealed detailed behavioral patterns of students, and these actions were related to the division into groups 2 and 3 (data in preparation for publication).
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Reliability of HI test in comparison with EIA Several reports have measured the antibody against measles by HI test, EIA, or enzyme-linked immunosorbent assay (ELISA) [14–18]. Many of these reports suggested the HI test was lower in sensitivity than EIA because falsenegative results were demonstrated in the HI test. However, as the HI test is cheaper than other methods, such as EIA and the plaque neutralization (PRN) test, it is a more useful method for wide-scale epidemical investigation than other methods. To investigate the reliability of the HI test, we compared the HI test results with these of EIA using all 103 postexposure blood samples. The HI titer and the EIA titer of the same samples were closely correlated; suggesting that titer as measured by HI test reliably reflects the trend of measles antibody. Effects of vaccination during measles epidemic Twenty-four (75%) subjects who were vaccinated during the period from April 21 to June 3 showed increases of more than fourfold in post-exposure HI titer. However, 8 students who were vaccinated did not show such increase. Five of them were vaccinated at least 1 month before the collection of post-exposure samples, and 3 other persons were vaccinated later, but all of them had a history of previous vaccination (data not shown). Thus, the reason for the low titers in these 8 cases is unknown. One possible inference is that in some cases vaccination is not enough to induce anti-measles antibody production. For sufficient induction of anti-measles antibody, additional stimulation, such as contagion with measles virus, may be necessary. In this study, because the supply of the vaccine was limited, 3 students with pre-exposure HI titers below 8 were not vaccinated. Two of them showed fever and catarrhal signs, and their post-exposure titers were significantly increased. Also, 14 students with pre-exposure titers B8 showed increase in their post-exposure titers and developed fever and/or catarrhal signs during the epidemic. On the other hand, 3 students who were vaccinated and had pre-exposure HI titers greater than 8 did not show significant increases in post-exposure titer and had no clinical signs. These results suggested that people with low preexposure titers (B8) would require the vaccine, and those with pre-exposure titers [8 would not require the vaccine for protection against viral infection.
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and pollinosis except for the high fever and rash. In our study, 22 of the non-cases had catarrhal signs (cough, runny nose, red watery eyes or light sensitivity, sore throat) and 10 showed these signs combined with mild fever. Nine of these subjects with pre-exposure titers B8 showed significant increased in their post-exposure titers. These 9 students apparently responded to vaccine and/or measles virus, and were suspected to have mild nonclassic measles, resembling modified measles. The students whose postexposure titers did not increase may not have been affected by the vaccine or measles virus, so their clinical signs would be derived from other diseases, such as pollinosis or the common cold. We cannot conclude that the clinical signs observed in the students whose post-exposure titers increased significantly were derived from measles. There are several other possibilities: pollinosis, general infection caused by various pathogens, and side effects of vaccination. Generally the catarrhal signs, such as excess mucous secretion and inflammation, increase the risk of spreading pathogens. Basic care such as handwashing and wearing masks are recommended for practical protection among individuals. Previous vaccination and history of measles Traditionally, it has been thought that once the immune system has been stimulated by wild measles virus, immunity will persist for life. Some reports agreed with this proposal [10, 22], whereas others suggested the possibility of reinfection and indicated the defective protection against measles infection in subjects with a history of prior infection with wild measles virus or a complete vaccination history [23, 24]. In the present study, subjects with a prior history of measles infection or with a record of two vaccinations did not develop measles. These results support the traditional theory of measles. The pre- and post-exposure HI titers of students with a history of measles or with two prior vaccinations were not different from those of other students. The number of vaccinations was not related to changes in HI titer or clinical signs. More information is required to discuss the necessary number of vaccinations. Our results support the plan for a two-dose measles vaccination schedule as recommended by the World Health Organization (WHO) and Centers for Disease Control (CDC) [2–4, 10].
Conclusion Clinical signs Previous reports have described modified atypical measles in children and young adults [19–21]. The clinical signs of mild measles are very similar to these of the common cold
Determination of pre-exposure HI titer is a reliable and practical method for identifying suitable candidates for measles vaccination. Our results indicated that vaccination during a measles epidemic succeeded in inducing anti-
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measles antibody production. Subjects with pre-exposure HI titers of 8 or less are recommended for measles vaccination to avoid individual infection and to prevent the expansion of measles infection within the community. The results of this study provided additional information for future measles control in Japan. Acknowledgments The authors thank the staff and students of the Faculty of Medicine of Teikyo University for their participation and cooperation in this study.
References 1. Griffin DE. Measles virus. In: Knipe DM, Howley PM, editors. Fields virology. 4th edn. Philadelphia: Lippincott Williams & Wilkins; 2001. p. 1401–41. 2. World Health Organization. Progress in reducing global measles death: 1999–2004. Wkly Epidemiol Rec. 2006;81:90–4. 3. National Institute of Infectious Disease and Tuberculosis and Infectious Disease Control Division, Ministry of Health, Labour and Welfare. Measles and rubella in Japan, as of March 2006. Infect Agents Surveill Rep. 2007;28:239–73. 4. Nagai M, Xin JY, Yoshida N, Miyata A, Fujino M, Ihara T, Yoshikawa T, Asano Y, Nakayama T. Modified adult measles in outbreak in Japan, 2007–2008. J Med Virol. 2009;81:1094–101. 5. Nagano H, Jinushi M, Tanabe H, Yamaguchi R, Okano M. Epidemiological and molecular studies of measles at different clusters in Hokkaido Distinct, Japan, 2007. Jpn J Infect Dis. 2009;62:209–11. 6. Kurata T, Miyagawa H, Furutani E, Kase T, Takahashi K. An outbreak of measles classified as genotype H1 in 2008 in Osaka Prefecture. Jpn J Infect Dis. 2009;62:76–7. 7. Morita Y, Suzuki T, Shiono M, Shiobara M, Saitoh M, Tsukagoshi H, et al. Sequence and phylogenetic analysis of nucleoprotein (N) gene in measles viruses prevent in Gunma, Japan, in 2007. Jpn J Infect Dis. 2007;60:402–4. 8. Ueda K, Miyazaki C, Hidaka Y, Okada K, Kusuhara R, Kadoya R. Aseptic meningitis caused by measles-mumps-rubella vaccine in Japan. Lancet. 1995;346:701–2. 9. Neumann PW, Weber JM, Jessamine AG, O’Shaughnessy MV. Comparison of measles antihemolysin test, enzyme-linked immunosorbent assay and hemagglutination inhibition test with neutralization test for determination of immune status. J Clin Microbiol. 1985;2:296–8.
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J Infect Chemother (2012) 18:341–346 10. Chen RT, Markowitz LE, Albrecht P, Stewart JA, Mofenson LM, Preblud SR, Orenstein WA. Measles antibody: reevaluation of protective titers. J Infect Dis. 1990;162:1036–42. 11. Linnemann CC, Rotte TC, Schiff GM. A seroepidemiologic study of a measles epidemic in a highly immunized population. Am J Epidemiol. 1972;95:238–46. 12. Krugman S. Further-attenuated measles vaccine: characteristic and use. Rev Infect Dis. 1983;5:477–81. 13. Orenstein WA, Herrmann KL, Albrecht P, Bernier R, Holmgreen O, Bart KJ, Hinman AR. Immunity against measles and rubella in Massachusetts schoolchildren. Dev Biol Stand. 1986;65:75–83. 14. Forghani B, Schmidt NJ. Antigen requirements, sensitivity, and specificity of enzyme immunoassays for measles and rubella viral antibodies. J Clin Microbiol. 1979;9(6):657–64. 15. Boteler WL, Luipersbeck PM, Fuccillo DA, O’Beirne AJ. Enzyme-linked immunosorbent assay for detection of measles antibody. J Clin Microbiol. 1983;17(5):814–8. 16. Weigle KA, Murphy MD, Brunell PA. Enzyme-linked immunosorbent assay for evaluation of immunity to measles virus. J Clin Microbiol. 1984;19(3):376–9. 17. Neumann PW, Weber JM, Jessamine AG, O’Shaughnessy MV. Comparison of measles antihemolysin test, enzyme-linked immunosorbent assay, and hemagglutination inhibition test with neutralization test for determination of immune status. J Clin Microbiol. 1985;22(2):296–8. 18. Souza VAUF, Pannuti CS, Sumita LM, Albrecht P. Enzymelinked immunosorbent assay (ELISA) for measles antibody. A comparison with haemagglutination inhibition, immunofluorescence and plaque neutralization tests. Rev Inst Med Trop Sa˜o Paulo. 1991;33(1):32–6. 19. Cherry JD, Feigin RD, Lobes LA, Shackelford PG. Atypical measles in children previously immunized with attenuated measles virus vaccine. Pediatrics. 1972;50:712–7. 20. Smith FR, Curran AS, Raciti A, Black FL. Reported measles in persons immunologically primed by prior vaccination. J Pediatr. 1982;101:391–3. 21. Wintermayer L, Myers MG. Measles in a partially immunized community. Am J Public Health. 1979;69:923–7. 22. Mathias RC, Meekison WG, Arcand TA, Schecter MT. The role of secondary vaccine failures in measles outbreaks. Am J Public Health. 1989;79:475–8. 23. Frank JA, Orenstein WA, Bart KJ, Bart SW, EL-Tantawy N, Davis RM, Hinman AR. Major impediments to measles elimination: the modern epidemiology of an ancient disease. Am J Dis Child. 1985;139:881–8. 24. Schaffner W, Schluederberg AES, Byrne EB. Clinical epidemiology of sporadic measles in a highly immunized population. N Engl J Med. 1988;279:783–9.
ORIGINAL ARTICLE
A case study of measles vaccination for university students during the measles outbreak in Tokyo, Japan, 2007 Ryuichi Fujisaki • Mariko Yamamura • Shigeru Abe • Kousuke Shimogawara • Michihiro Kasahara • Hajime Nishiya • Miho Makimura • Koichi Makimura
Received: 16 December 2010 / Accepted: 25 October 2011 / Published online: 3 December 2011 Ó Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases 2011
Abstract In April 2007, seven students belonging to the same class at Teikyo University developed measles. To prevent the spread of infection, 27 of 106 students in the same class who had low anti-measles antibody titers as measured by hemagglutination inhibition (HI) assay were vaccinated. After the outbreak had subsided, the HI values were investigated in 103 students, and they answered questionnaires about their health condition during the period of the outbreak and their previous clinical histories of measles, including vaccination records. There was no R. Fujisaki Emergency Room of Teikyo University Hospital, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan M. Yamamura Department of Internal Medicine, Faculty of Medicine, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan S. Abe M. Makimura K. Makimura (&) Teikyo University Institute of Medical Mycology, Teikyo University, 356 Otsuka, Hachioji, Tokyo 192-0395, Japan e-mail: [email protected] K. Shimogawara Laboratory of Chemistry, Faculty of Medicine, Teikyo University, 356 Otsuka, Hachioji, Tokyo 192-0395, Japan M. Kasahara Laboratory of Biophysics, Faculty of Medicine, Teikyo University, 356 Otsuka, Hachioji, Tokyo 192-0395, Japan H. Nishiya School of Medical Technology, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan K. Makimura Laboratory of Space and Environmental Medicine, Graduate School of Medicine, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan
new case of measles after introduction of the vaccination program. However, the HI titers of 42% of the students who were not vaccinated in this program were significantly elevated. Fever and catarrhal signs occurred in 7 of these students with pre-exposure titers of 8 or less. The postexposure HI titers of 71% of students who were unaffected by measles and had high HI titers ([8) before the epidemic did not increase. These results suggested that people with low HI titers may become potential carriers of measles and that measurement of pre-exposure HI anti-measles antibody titer is a useful method for selection of candidates to undergo vaccination. Keywords Measles Vaccination Outbreak Student Hemagglutination inhibition (HI) Enzyme immunoassay (EIA)
Introduction Measles virus causes acute infectious disease in humans [1, 2] and is the etiological agent one of the most important lethal infections in young children. Measles infection shows several clinical signs, i.e., cough, coryza, high fever, maculopapular rash, conjunctivitis, and complications of pneumonia and/or encephalitis in some cases, which occasionally results in death. In 2001, there was a nationwide outbreak of measles in Japan. Most patients affected in this outbreak were infants and young children [3]. Following this measles outbreak, the government of Japan strengthened the measles surveillance system in each prefecture and promoted a nationwide campaign of vaccination for children. These attempts resulted in a marked reduction in the measles infection rate among younger people. However, in 2006 a small local prevalence of
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342
measles led to an outbreak in Japan that lasted until the summer of 2007 [3]. The outbreak in 2007 was different from previous outbreaks in that the majority of patients were young adults or adolescents attending high schools and university students [3–7]. Measles vaccination in Japan started in 1978. The majority of people born before 1978 had no history of measles vaccination, but their antibody titers against measles are sufficiently high to avoid infection, which can be explained by natural sensitization to measles. Younger generations show reduced levels of antibodies against measles [3, 4], which is considered to be caused by the decrease in the opportunity for natural sensitization and lack of complete vaccination. From 2006, two dosage schedules were started, at 1 year and at 5–6 years of age, but this system could not prevent the measles outbreak in summer of 2007. The Japanese government implemented a 5-year vaccination catch-up campaign for cohorts aged 13 and 18 years to prevent future outbreaks of measles [3] from 2008. However, complete vaccination in this generation seems not to be actually possible for social and economic reasons. In addition, some persons avoid vaccination because of highly publicized problems with measles, mumps, and rubella (MMR) vaccine between 1989 and 1993 in Japan [8]. Practically, it is necessary to present reasonable criteria of vaccination. In this study, we used the hemagglutination inhibition (HI) test for measurement of antibody activity against measles. The HI test is generally less sensitive than enzyme immunoassay (EIA) [9]. However, HI is a simpler and lower-cost method than EIA. In addition, the HI test does not require specialized instruments or techniques and can therefore be introduced conveniently into small laboratories. Here, we investigated pre- and post-HI titers of 103 students exposed to a measles outbreak. The clinical condition and previous history of measles and vaccine records of all subjects were also investigated.
Materials and methods
J Infect Chemother (2012) 18:341–346
departments by their special lecture schedule. They also lived within a very limited area around the university. Study population A total of 103 of the 106 students provided informed consent to participation in this study. The average age of subjects was 22 years old. These 103 subjects included 7 students who developed measles. Titration of antibodies against measles by HI test and EIA (serological tests) The anti-measles antibody titers of the first-grade medical school students were measured by hemagglutination inhibition (HI) test [7] before the beginning of their first school session (10 April 2007). These results were used as the preexposure titers. HI tests performed using commercial kits obtained from SRL (Tokyo, Japan) involved measuring HI titers by testing endpoint serial dilution of blood samples for hemagglutination inhibition. In this study, an increase in post-exposure HI titers of more than fourfold compared to the pre-exposure value was determined to be significant. Post-exposure blood samples were obtained on June 11, when we confirmed the end of the measles epidemic at this university because no new patient had been observed for 1 month. The blood samples of 103 subjects were investigated as post-exposure titers by HI test and EIA (SRL). Clinical condition and vaccination history Information from participants concerning symptoms experienced during the outbreak was obtained by selfadministered questionnaires. Signs and symptoms elicited on the questionnaire included fever and catarrhal symptoms (cough, runny nose, red watery eyes or light sensitivity, sore throat), headache, and diarrhea. Information about previous and recent vaccinations and measles history were obtained from students, parents, and provider-verified birth records.
Background Vaccination During the period from March to May 2007, 7 students in the first grade of the Faculty of Medicine on Teikyo University Hachioji campus developed measles. A total of 106 students belonged to the same class. The first case was observed in March, and the last case was detected on April 29. The university is located in the eastern part of Tokyo; the students of the medical school all belonged to the same class and were isolated from other students from different
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There was a serious shortage of measles vaccine in Japan in spring 2007. Some students who wished to receive the vaccination could not do so because of insufficient availability of the vaccine. The 27 subjects with low HI titers (\8) and 5 with HI titers C8 who strongly desired vaccination had the vaccination between April 21 and June 3; a total of 32 subjects were vaccinated (one time/person).
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Results Measles patients (cases) The data for seven students diagnosed with measles during the period between March and May 2007 are shown in Table 1. One student (case 6) developed measles illness between March 26 and April 7 and was considered to have recovered from the illness before collection of the pre-exposure blood sample (Table 1). Case 1 showed mild clinical signs of measles at pre-exposure blood sample collection and may have been in the very early stages of infection at this point. Pre-exposure samples from all cases had low titers (\8) of HI, except for case 6, who had recently recovered from measles. The post-exposure titers of six students diagnosed with measles (all positive cases except case 6) significantly increased (4- to 128-fold higher than pre-exposure titers). The clinical manifestations in these cases were all consistent with classical measles symptoms, i.e., fever, confluent maculopapular rash, and cough, coryza, or conjunctivitis. Pre-exposure HI titers: comparison between cases and non-cases Six of the seven students affected with measles after preexposure sampling had the lowest HI titers (\8). Subjects who did not have clinical measles had antibody titers ranging from\8 to 256 (data not shown). Fifty-seven of 96 students had HI titers B8 (59%). Thirty-nine students (41%) had HI titers [16 [HI titer: 256 (n = 1), 128 (n = 6), 64 (n = 1), 32 (n = 11), 16 (n = 20) (data not shown)]. The average HI titers in cases and non-cases were 8 and 23, respectively.
(75%) showed increases in HI titer of more than fourfold compared to the pre-exposure value. None of the subjects with pre-exposure titers [8 showed an increase in postexposure titer. In the non-vaccinated group (64 students), 27 subjects (42%) showed increases in HI titer of more than fourfold compared to the pre-exposure value. Nonvaccinated subjects with pre-exposure titers of 8 or less included 7 who showed both fever and catarrhal signs (Table 2). Only 1 non-vaccinated student with a titer \8 showed fever (Table 2). Comparison of the results of HI test with those of EIA We compared the results of HI test and those of EIA using all post-exposure blood samples (Fig. 1). The HI titers of subjects were closely correlated to the values determined by EIA. Table 2 cases
Change of hemagglutination inhibition (HI) titer in non-
Non-case (n = 96)
C4 fold
\4 fold
Vaccinated (n = 32) Pre titer \8
22 (7/2)a
Pre titer = 8
2 (0/0)
Pre titer [8 Non-vaccinated (n = 64)
a
0
5 (1/0) 0 3 (0/0)
Pre titer \8
2 (2/2)
1 (0/0)
Pre titer = 8
14 (5/5)
11 (1/0)
Pre titer [8
11 (1/0)
25 (5/1)
Clinical signs: catarrh/fever
Pre titer, pre-exposure titer
Pre- and post-exposure HI titers: non-cases The increase in HI titer of non-cases was investigated (Table 2). In the vaccine group (32 students), 24 subjects
Table 1 Hemagglutination inhibition (HI) titer and clinical information of cases Case
Pre titer
Post titer
Previous measles
Previous vaccinations
Measles illness
1
\8
256
–
Unknown
2
\8
1,024
–
0
April 25–May 5
3 4
\8 \8
1,024 32
– –
Unknown 0
April 25–April 30 April 22–April 28
5
\8
512
–
Unknown
6
32
64
–
0
7
\8
1,024
–
1
April 7–April 14
April 22–May 2 March 26–April 7 April 23–April 28
Pre titer, pre-exposure titer; Post titer, post-exposure titer
Fig. 1 Comparison of titers determined by hemagglutination inhibition (HI) and enzyme immunoassay (EIA). The HI and EIA titers of 103 individuals are expressed as small points (small filled circles). Average values are expressed as large symbols (large filled circles). Standard differences are indicated by vertical bars
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Table 3 Previous measles and vaccination history of cases and non-cases Case of measles
Pre titer
Post titer
\8
=8
[8
\4-fold
Clinical signs C4-fold
Previous measles (n = 11)
0
4
1
6
5
6
2
Previous vaccine, 0 (n = 10)
3
3
0
7
4
6
3
Previous vaccine, 1 (n = 54)
1
18
18
18
22
32
18
Previous vaccine, 2 (n = 9)
0
5
2
2
4
5
2
Unknown (n = 30)
3
10
8
12
15
15
4
Clinical signs: catarrh and/or fever Pre titer, pre-exposure titer; Post titer, post-exposure titer
Relationships between previous vaccinations and history of measles and resistance to infection In this study, the students who had histories of measles infection and with records of vaccination with two doses did not develop typical measles illness (Table 3). However, history of measles and number of previous vaccinations were not related to pre- or post-exposure HI titers in either cases or non-cases.
Discussion Sporadic outbreaks of measles occurred in Japan from 2006 to 2007 [3–7]. In many cases, outbreaks were reported from distinct capitals, and occurred in schools with students aged 10–20 years old. There have been several reports regarding phylogenetic analysis of measles virus [5–7]. However, there have been few reports of pre- and post-exposure anti-measles antibody levels. Chen et al. [10] reported a large-scale measles epidemic in the dormitories of Boston University (USA). They investigated pre- and post-exposure blood samples and reported changes in specific anti-measles antibody using EIA and the plaque reduction neutralization (PRN) test. In this study, we collected serological and clinical information for 103 students exposed to measles and investigated the effects of vaccination in students with low levels of anti-measles antibody to establish a concrete strategy for preventing the expansion of measles outbreaks. Significance of pre-exposure HI titer The presence of detectable measles antibody has been thought to indicate that an individual would be protected against falling ill if exposed to the measles virus. However, there have been only a few reports regarding pre-exposure anti-measles antibody titer [10, 11]. In this study, we used the HI test for measurement of anti-measles antibody titers. The standard HI test, a
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traditional assay, is less sensitive than EIA and the PRN assay [9, 12, 13]. However, the HI test can be performed easily and does not require special techniques or expensive equipment. Thus, we gave priority to the convenience, rapidity, and practical applicability of the HI test. The results of the present study using the HI test suggested that a titer [8 was required for protection against measles. All patients in this study had HI pre-exposure titers \8, with the exception of case 6 who had recently recovered from illness before pre-exposure sampling. The 30 subjects who had low pre-exposure titers (\8) did not develop measles (Table 2). Using the PRN assay, Chen et al. [10] suggested that a titer [120 mIU/ml was required for protection against falling ill with measles. The number of patients in our study was too small to determine the border value; however, at least the subjects whose pre-exposure HI titer was \8 were susceptible to measles infection. Post-exposure HI titers From the point of view of post-exposure titer change, the 103 students were divided into three groups: group 1 consisted of 7 cases of measles; group 2 consisted of 51 non-cases whose post-HI titers increased by more than fourfold; and group 3 consisted of 45 non-cases whose post HI titers did not increase. The subjects in group 2 had preexposure HI titers \8 (47%), 8 (31%), and [8 (22%). On the other hand, 13%, 24%, and 62% of subjects in group 3 had pre-exposure HI titers \8, 8, and [8, respectively. Group 2 included 9 subjects who showed fever and catarrhal signs during the epidemic period; group 3 included only 1 of these subjects. Comparison of the results suggested that the students in group 2 responded to vaccination and/or measles virus, and the subjects with low pre-exposure titers (B8) were more affected by the measles than those with high pre-exposure titers ([8). Interestingly, the questionnaires regarding the relationships between students revealed detailed behavioral patterns of students, and these actions were related to the division into groups 2 and 3 (data in preparation for publication).
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Reliability of HI test in comparison with EIA Several reports have measured the antibody against measles by HI test, EIA, or enzyme-linked immunosorbent assay (ELISA) [14–18]. Many of these reports suggested the HI test was lower in sensitivity than EIA because falsenegative results were demonstrated in the HI test. However, as the HI test is cheaper than other methods, such as EIA and the plaque neutralization (PRN) test, it is a more useful method for wide-scale epidemical investigation than other methods. To investigate the reliability of the HI test, we compared the HI test results with these of EIA using all 103 postexposure blood samples. The HI titer and the EIA titer of the same samples were closely correlated; suggesting that titer as measured by HI test reliably reflects the trend of measles antibody. Effects of vaccination during measles epidemic Twenty-four (75%) subjects who were vaccinated during the period from April 21 to June 3 showed increases of more than fourfold in post-exposure HI titer. However, 8 students who were vaccinated did not show such increase. Five of them were vaccinated at least 1 month before the collection of post-exposure samples, and 3 other persons were vaccinated later, but all of them had a history of previous vaccination (data not shown). Thus, the reason for the low titers in these 8 cases is unknown. One possible inference is that in some cases vaccination is not enough to induce anti-measles antibody production. For sufficient induction of anti-measles antibody, additional stimulation, such as contagion with measles virus, may be necessary. In this study, because the supply of the vaccine was limited, 3 students with pre-exposure HI titers below 8 were not vaccinated. Two of them showed fever and catarrhal signs, and their post-exposure titers were significantly increased. Also, 14 students with pre-exposure titers B8 showed increase in their post-exposure titers and developed fever and/or catarrhal signs during the epidemic. On the other hand, 3 students who were vaccinated and had pre-exposure HI titers greater than 8 did not show significant increases in post-exposure titer and had no clinical signs. These results suggested that people with low preexposure titers (B8) would require the vaccine, and those with pre-exposure titers [8 would not require the vaccine for protection against viral infection.
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and pollinosis except for the high fever and rash. In our study, 22 of the non-cases had catarrhal signs (cough, runny nose, red watery eyes or light sensitivity, sore throat) and 10 showed these signs combined with mild fever. Nine of these subjects with pre-exposure titers B8 showed significant increased in their post-exposure titers. These 9 students apparently responded to vaccine and/or measles virus, and were suspected to have mild nonclassic measles, resembling modified measles. The students whose postexposure titers did not increase may not have been affected by the vaccine or measles virus, so their clinical signs would be derived from other diseases, such as pollinosis or the common cold. We cannot conclude that the clinical signs observed in the students whose post-exposure titers increased significantly were derived from measles. There are several other possibilities: pollinosis, general infection caused by various pathogens, and side effects of vaccination. Generally the catarrhal signs, such as excess mucous secretion and inflammation, increase the risk of spreading pathogens. Basic care such as handwashing and wearing masks are recommended for practical protection among individuals. Previous vaccination and history of measles Traditionally, it has been thought that once the immune system has been stimulated by wild measles virus, immunity will persist for life. Some reports agreed with this proposal [10, 22], whereas others suggested the possibility of reinfection and indicated the defective protection against measles infection in subjects with a history of prior infection with wild measles virus or a complete vaccination history [23, 24]. In the present study, subjects with a prior history of measles infection or with a record of two vaccinations did not develop measles. These results support the traditional theory of measles. The pre- and post-exposure HI titers of students with a history of measles or with two prior vaccinations were not different from those of other students. The number of vaccinations was not related to changes in HI titer or clinical signs. More information is required to discuss the necessary number of vaccinations. Our results support the plan for a two-dose measles vaccination schedule as recommended by the World Health Organization (WHO) and Centers for Disease Control (CDC) [2–4, 10].
Conclusion Clinical signs Previous reports have described modified atypical measles in children and young adults [19–21]. The clinical signs of mild measles are very similar to these of the common cold
Determination of pre-exposure HI titer is a reliable and practical method for identifying suitable candidates for measles vaccination. Our results indicated that vaccination during a measles epidemic succeeded in inducing anti-
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measles antibody production. Subjects with pre-exposure HI titers of 8 or less are recommended for measles vaccination to avoid individual infection and to prevent the expansion of measles infection within the community. The results of this study provided additional information for future measles control in Japan. Acknowledgments The authors thank the staff and students of the Faculty of Medicine of Teikyo University for their participation and cooperation in this study.
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