- Email: [email protected]
The 23-valent pneumococcal polysaccharide vaccine does not provide additional serotype antibody protection in children who have been primed with two doses of heptavalent pneumococcal conjugate vaccine
Vaccine 25 (2007) 6321–6325
The 23-valent pneumococcal polysaccharide vaccine does not provide additional serotype antibody protection in children who have been primed with two doses of heptavalent pneumococcal conjugate vaccine Paul Balmer a , Ray Borrow a , Peter D. Arkwright b,∗ a
Health Protection Agency, Clinical Sciences Building II, Manchester Royal Infirmary, Oxford Road, Manchester M13 9WL, United Kingdom b University of Manchester, Booth Hall Children’s Hospital, Charlestown Road, Manchester M9 7AA, United Kingdom Received 14 April 2007; received in revised form 4 June 2007; accepted 11 June 2007 Available online 29 June 2007
Abstract Current guidelines recommend up to two doses of the pneumococcal conjugate heptavalent vaccine (PCV-7) in children up to 5 years old followed by and a dose of the polysaccharide vaccine (PPV-23) for patients over 2 years old to broaden serotype immunity. We assessed the serotype responses to two doses of PCV-7 and a dose of PPV-23 in a cohort of children in the 2–16-year age range in order to determine whether PPV-23 induced effective immunity to non-PCV-7 serotypes. Pneumococcal antibody concentrations to the seven serotypes covered by PCV-7 and five additional serotypes covered by PPV-23 but not PCV-7 were measured in 60 children aged 2–16 years. None of the children had a primary antibody immunodeficiency. Vaccinated children had 7–30-fold higher antibody concentrations than unvaccinated children to all serotypes contained in the PCV-7 (P < 0.001). In contrast, serotypes covered by the PPV-23 but not PCV-7 were only one- to two-fold higher and there was no significant increase in the number of children who had protective concentrations of antibody (≥0.35 mcg/ml) against these serotypes. In this cohort of children, PPV-23 vaccine did not broaden the protection in vitro against potentially pathogenic strains of Streptococcus pneumoniae. We call into question the recommendation to use the PPV-23 in children. © 2007 Elsevier Ltd. All rights reserved. Keywords: Streptococcus pneumoniae; Pneumococcal antibodies; Serotypes; Vaccine; Children
1. Introduction Invasive pneumococcal disease leads to significant morbidity and mortality in both children and adults [1,2]. In children in England and Wales, 80% of invasive infections are caused by 8–10 capsular strains [3]. The heptavalent pneumococcal conjugate vaccine (PCV-7) was introduced into the UK in 2002 for at risk groups under 2 years old. From 2006 it has been included into the routine infant vaccination schedule. For children and adults in certain clinical risk groups, for example patients with chronic respiratory, renal or liver disease, congenital heart disease, patients with cochlear implants ∗
Corresponding author. Tel.: +44 161 918 5112; fax: +44 161 918 5143. E-mail address: peter [email protected] (P.D. Arkwright).
0264-410X/$ – see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.vaccine.2007.06.021
and patients with no functioning spleen, up to two doses of PCV-7 are recommended in children under 5 years old, followed by a dose of pneumococcal polysaccharide vaccine (PPV-23) for any patient over 2 years old to broaden protection against serotypes not covered by the PCV-7 vaccine [4]. The PCV-7 has been shown to provide excellent protection against invasive pneumococcal disease including pneumonia caused by the seven serotypes covered by the vaccine [5–7]. In contrast, it is difficult to reach firm conclusions about the clinical effectiveness of PPV-23, which seems to be around 50–70% effective in terms of preventing pneumococcal bacteraemia. There is no evidence that this vaccine prevents non-bacteraemic pneumococcal pneumonia or otitis media, or reduces mortality from pneumococcal infection [8–11].
6322
P. Balmer et al. / Vaccine 25 (2007) 6321–6325
In a previous study, we showed that after vaccination of children with two doses of PCV-7 followed by a dose of PPV-23, there was significant increases in the concentration in all serotypes covered by PCV-7, but no change in the concentration of two pneumococcal serotypes (1 and 5) covered by PPV-23 but not PCV-7 [12]. These data called into question the immunogenicity of PPV-23, at least in children aged 2–16 years old. In this study we extend and consolidate these findings by examining the differences in 12 serotype concentrations, 7 covered by PCV-7 and 5 only covered by PPV-23 after vaccination with 2 doses of PCV-7 followed by a dose of PPV-23. The study shows a clear lack of immunogenicity of the PPV-23, and an inability of this vaccine to broaden the protection of children against potentially pathogenic pneumococcal serotypes in children.
2. Materials and methods 2.1. Patients Patients for inclusion in the study were identified from a database of stored serum samples, which had been received between August 2002 and August 2005 by the Vaccine Evaluation Unit, North West HPA Regional Laboratory in Manchester. Limited pneumococcal serotype responses (seven PCV-7 serotypes as well as serotypes 1 and 5) had previously been performed on these samples, but were repeated with the additional analysis of a further three non-PCV-7 serotypes (serotypes 2, 7F, and 19A). Only children aged 16 years or less (median age 5 years) for whom detailed hospital records were available for review were included in the analysis. All patients had been referred to a single paediatric immunology clinic with a history of symptoms of respiratory infections. Patients with underlying primary antibody deficiencies (defined as those with serum immunoglobulin concentrations below the normal age-related ranges and non-protective responses post-tetanus and Haemophilus influenzae type b vaccination) were excluded. At the time of analysis, 97% of patients had been discharged from followup. Pneumococcal antibody levels were available on 37 children prior to any pneumococcal vaccination and on 27 after vaccination, which in all cases had involved giving two doses of the PCV-7 (Prevenar, Wyeth Pharmaceuticals, Herts, United Kingdom) and then one dose of PPV-23 (Pneumovax II, Pasteur Merieux MSD Ltd. Herts, United Kingdom) at monthly intervals. Blood for antibody measurements were taken at a median (inter-quartile range) time of 2 (1–4) months after the final PPV-23 vaccine. Only in 4 of the 60 children were paired pre- and post-vaccination samples available for analysis. Age (median (inter-quartile range) 5 (3–10) years versus 6 (3–10) years; P = 1.0), gender (57% males versus 48% males, P = 0.5) and ethic background (89% Caucasian versus 92% Caucasian, P = 1.0) distributions of the pre- and post-vaccination groups were not statistically different. The research project was granted ethics approval by the local
research ethics committee and consent was obtained from parents of all patients. There was no external funding for this study. 2.2. Multiplex fluorescent bead assay for the quantitative detection of serum IgG antibodies to Streptococcus pneumoniae capsular polysaccharides Twelve different pneumococcal serotype concentrations (1, 3, 4, 5, 6B, 7F, 9V, 14, 18C, 19A, 19F, 23F) were assayed by a two-step procedure as previously described [13,14]. Pneumococcal polysaccharide antigens were initially conjugated to microspheres. The polysaccharide is coupled to poly-l-lysine and conjugated to the microspheres by a twostep carbodiimide reaction using EDC with sulpho-NHS and cyanuric chloride and purified down a Sephadex column. The assays were performed in 96-well microtitre filter plates using 25 l of the standards and diluted samples. As the patient’s samples were diluted at 1 in 100 only 5 l of sera was required for the assays. A double adsorption step of sera with both C-Ps and type 22F pneumococcal polysaccharide was performed. This was, followed by the addition of 5000 beads/region/25 l, and then 100 l of 1:200 dilution of R-phycoerythrin conjugated anti-human IgG (Jackson ImmunoResearch Lab, West Grove, USA) in PBS (binding all IgG subclasses) with 20 min incubations. Assays were done in duplicate and read using a Bioplex protein array system (Bio-Rad, Herts, United Kingdom). Results were reported as individual IgG antibody concentrations (g/ml) to each of the 12 pneumococcal serotypes in the assay. A serum pneumococcal serotype concentration ≥0.35 g/ml is now suggested as providing adequate protection against pneumococcal infection in infants [15,16]. 2.3. Statistical analysis Data were analysed using SPSS 12.0 software package (SPSS Inc., Chicago, USA). As much of the data was found not to be normally distributed non-parametric statistics were used throughout. Medians (inter-quartile ranges) are quoted for continuous variables. The Mann–Whitney U-test was used to check for statistical differences between these data groups. Chi-square statistic was used for discrete data. Because of the number of comparisons, differences between groups were documented as being significant only if P values were <0.01.
3. Results 3.1. Demographic and clinical characteristics of study cohort Sixty children aged 2–16 years (median 5 years) of whom 30 (50%) were male were included in the study. Twenty-five (42%) patients had a history of respiratory infections, 2 (3%)
P. Balmer et al. / Vaccine 25 (2007) 6321–6325
6323
Fig. 1. Box-plots showing pneumococcal serotype concentrations in children who have not been vaccinated against Streptococcus pneumoniae (unfilled boxes) and those that have had two doses of PCV-7 followed by a dose of PPV-23 (hatched boxes). Median (thick bar) and quartiles (box). Serotypes with asterisks are covered by PCV-7. **P < 0.001 by Mann–Whitney U-test, other comparisons were not statistically different.
a history of meningococcemia, but in the remainder there was no specific clinical indication within the hospital records for why the pneumococcal antibody test had been requested. Fifty-eight (97%) of children had been discharged from further follow-up. There was no evidence from measurement of serum immunoglobulins and specific antibodies to other vaccines (tetanus and Haemophilus influenzae, type b) of an underlying antibody immunodeficiency. 3.2. Pneumococcal serotype-specific concentrations in unvaccinated children and after two doses of PCV-7 followed by a dose of PPV-23 Pneumococcal serotype-specific IgG covered (serotypes 4, 6B, 9V, 14, 18C, 19F and 23F) and not covered (serotype 1, 3, 5, 7F and 19A) by PCV-7 were studied. In vaccinated children concentrations of serotypes covered by the PCV-7 vaccine were 7–30-fold higher, in contrast to concentrations of serotypes covered by the PPV-23 but not the PCV-7 vaccine
which were only one- to two-fold higher than in unvaccinated children (Fig. 1). Natural protection (defined as serotype concentrations ≥0.35 g/ml) in unvaccinated children ranged from 11% of children for pneumococcal serotype 6B to 65% of children for serotype 3, indicating variation in environmental exposure to these potential pathogens (Table 1). After pneumococcal vaccination, protection against serotypes covered by the PCV-7 vaccine was significantly enhanced to between 82 and 100%. In contrast, there was no significant difference in the percentage of children protected against serotypes covered by the PPV-23 but not PCV-7 vaccine, where levels of protection remained at between 44 and 82%. 3.3. Effect of age on children’s response to vaccination There was no significant correlation between the age of the child and the post-vaccination concentrations of any of the 12 serotypes studied, as measured using Spearman correlation
6324
P. Balmer et al. / Vaccine 25 (2007) 6321–6325
Table 1 Proportion of children with pneumococcal serotype concentrations ≥0.35 g/ml n Age (years) Males (%) P1 P3 P5 P7F P19A P4* P6B* P9V* P14* P18* P19F* P23F*
No vaccination
Post-vaccine
P value
37 5 (3–10) 21 (57) 13 (35) 24 (65) 14 (38) 15 (40) 14 (38) 7 (19) 4 (11) 14 (38) 19 (51) 8 (22) 14 (51) 13 (35)
27 6 (3–10) 13 (48) 13 (48) 22 (82) 12 (44) 14 (52) 14 (52) 23 (85) 22 (82) 24 (89) 26 (96) 27 (100) 23 (85) 23 (85)
1.0 0.6 0.6 0.2 0.6 0.5 0.3 0.0001 0.0001 0.0001 0.0001 0.0001 0.01 0.0001
Table compares children who have never had any pneumococcal vaccinations with those who have been vaccinated with two doses of PCV-7 followed by a dose of PPV-23. Age is given in median (inter-quartile range). Data for serotype are given as number (percentage) with antibody concentrations ≥0.35 g/ml. Serotypes with asterisk are those covered by PCV-7. P value is calculated using Chi-square analysis.
coefficient or comparing groups of children aged 2–5 years old and children aged 6–16 years old (data not shown). There were no significant age or gender differences between the preand post-vaccination groups (Table 1).
4. Discussion This study clearly shows the lack of in vitro immunogenicity of the PPV-23 vaccine in children, when compared with the excellent pneumococcal serotype responses to the conjugate vaccine PCV-7. These data complement the clinical data from three metaanalyses, which showed that the PPV-23 vaccine offers little or no protection against pneumonia or death from S. pneumoniae in adults, but may have some protective effect against invasive disease in the elderly, particularly those with higher risk of this infection [9–11]. Although the numbers in the study are small, the data are highly significant and there are clear differences between serotype responses to PCV-7 and PPV-23. PCV-7 is known to stimulate an IgG1 subclass response while PPV-23 stimulates an IgG2 subclass response [12,17]. The multiplex assay detects both IgG1 and IgG2 antibodies and therefore the differences in vaccine efficacy cannot be put down to restricted measurement of one but not another immunoglobulin subclass. Our previous study demonstrated that the antibody response to Prevenar in children is IgG1 subclass specific [12]. The study is limited to analysis of sera samples available in the Vaccine Evaluation Unit in Manchester prior to addition of PCV-7 to the infant national vaccination schedule in 2006. Ideally paired pre- and post-vaccination sera should have been studied, but unfortunately these were only avail-
able from 4 of the 60 children. The pre- and post-vaccination groups were however comparable for age, gender and ethnic origin. The group of children studied here was considered at “higher risk” of infection with S. pneumoniae infections based on the history of recurrent respiratory infections, even though specific underlying antibody immunodeficiency disorders were not found in any of the children and 97% were discharged from further follow-up. This cohort would therefore seem a more appropriate study group in order to test the current pneumococcal vaccination guidelines for “high risk” groups. The results presented may however not predict the pneumococcal responses of a “health cohort” of children from the general population. In summary, there is no evidence from this study to support the current recommendations made by expert opinion in the latest edition of immunisation against infectious disease [4] for the addition of PPV-23 to the vaccination schedule for children in “clinical risk groups”. There is some suggestion that prior administration of meningococcal polysaccharide vaccines may interfere with the response to subsequent meningococcal conjugate vaccines [18], although this may not be the case for pneumococcal vaccines [19]. Thus although the PPV-23 vaccine may of limited efficacy, it does not seem to do any harm. The question that now needs to be addressed is that with the introduction of PCV-7 into routine use and the likely introduction of further multi-conjugate pneumococcal vaccines onto the market in the next few years (PCV-13 and PCV-10) [20–23], is there any role for the PPV23 in children. Based on the data presented, our personal recommendations are that (1) PCV-7 should replace PPV-23 for all high risk children, not just those less than 5 years old, requiring immunisation against community acquired S. pneumoniae and (2) the use of PPV-23 as an additional booster following PCV-7 should be discontinued or at least be reevaluated.
Acknowledgement We would like to acknowledge Michael Wilding for immunoassay performance. Conflict of interest statement: Dr. Balmer has received assistance to attend scientific meetings from Wyeth Vaccines, Baxter Bioscience and Chiron Vaccines. Industry honoraria received for lecturing are paid directly into Central Manchester and Manchester Children’s University Hospitals NHS Trust endowment fund. Dr. Borrow has received assistance to attend scientific meetings from Wyeth Vaccines and Baxter Bioscience and has served as a consultant for GlaxoSmithKline, Fujisawa GmbH, Sanofi Pasteur and Baxter Bioscience. Industry honoraria received for consulting, lecturing and writing are paid directly into Central Manchester and Manchester Children’s University Hospitals NHS Trust endowment fund. Dr. Borrow has performed contract research on behalf of the Health Protection Agency (funded by Wyeth Vaccines, Chiron Vaccines, Baxter Bioscience,
P. Balmer et al. / Vaccine 25 (2007) 6321–6325
GlaxoSmithKline, Sanofi Pasteur, Fujisawa GmbH, Alexion Pharmaceuticals Inc., Microscience Ltd. and Xenova Research Ltd. Dr. Arkwright declares no conflicts of interest.
References [1] Williams BG, Gouws E, Boschi-Pinto C, Bryce J, Dye C. Estimates of world-wide distributions of child deaths from acute respiratory infections. Lancet Infect Dis 2002;2:25–32. [2] Fedson DS, Scott JA. The burden of pneumococcal disease among adults in developed and developing countries: what is and is not known. Vaccine 1999;17(Suppl 1):S11–8. [3] www.hpa.org.uk/infections/topics az/pneumococcal/. [4] Immunisation against infectious disease “The Green Book”. In: Salsbury D, Ramsay M, Noakes K, editors. Department of Health, U.K. TSO 2006 Third Edition. www.dh.gov.uk/PolicyAndGuidance/HealthAndSocialCareTopics/GreenBook/GreenBookGeneralInformation/ GreenBookGeneralArticle/fs/en?CONTENT ID=4097254&chk =isTfGX. [5] Black S, Shinefield H, Fireman B, Lewis E, Ray P, Hansen JR, et al. Efficacy, safety, and immunogenicity of heptavalent pneumococcal conjugate vaccine in children. Pediatr Infect Dis J 2000;19:187–95. [6] Black S, Shinefield HR, Ling S, Hansen J, Fireman B, Spring D, et al. Effectiveness of heptavalent pneumococcal conjugate vaccine in children younger than 5 years of age for prevention of pneumonia. Pediatr Infect Dis J 2002;21:810–5. [7] Black S, Shinefield H, Baxter R, Austrian R, Elvin L, Hansen J, et al. Impact of the use of heptavalent pneumococcal conjugate vaccine on disease epidemiology in children and adults. Vaccine 2006;24(Suppl 2):S2–80. [8] Butler JC, Breiman RF, Campbell JF, Lipman HB, Broome CV, Facklam RR. Pneumococcal polysaccharide vaccine efficacy. An evaluation of current recommendations. JAMA 1993;270:1826–31. [9] Dear K, Holden J, Andrews R, Tatham D. Vaccines for preventing pneumococcal infection in adults. Cochrane Database Syst Rev 2003;4. CD000422. [10] Mangtani P, Cutts F, Hall AJ. Efficacy of polysaccharide pneumococcal vaccine in adults in more developed countries: the state of the evidence. Lancet Infect Dis 2003;3:71–8. [11] Melegaro A, Edmunds WJ. The 23-valent pneumococcal polysaccharide vaccine. Part I. Efficacy of PPV in the elderly: a comparison of meta-analyses. Eur J Epidemiol 2004;19:353–63.
6325
[12] Uddin S, Borrow R, Haeney MR, Moran A, Warrington R, Balmer P, et al. Total and serotype-specific pneumococcal antibody titres in children with normal and abnormal humoral immunity. Vaccine 2006;24:5637–44. [13] Lal G, Balmer P, Stanford E, Martin S, Warrington R, Borrow R. Development and validation of a nonaplex assay for the simultaneous quantitation of antibodies to nine Streptococcus pneumoniae serotypes. J Immunol Meth 2005;296:135–47. [14] Borrow R, Balmer P. Assessment of functional antibody responses. Meth Mol Med 2003;87:289–300. [15] World Health Organisation. Pneumococcal conjugate vaccines. Recommendations for the production and control of pneumococcal conjugate vaccines. WHO Tech. Rep. Ser. 2005;927:64–98. [16] Siber GR, Chang I, Baker S, Fernsten P, O’Brien KL, Santosham M, et al. Estimating the protective concentration of anti-pneumococcal capsular polysaccharide antibodies. Vaccine 2007 February 21 [Epub ahead of print]. [17] Barrett DJ, Ayoub EM. IgG2 subclass restriction of antibody to pneumococcal polysaccharides. Clin Exp Immunol 1986;63:127–34. [18] Southern J, Deane S, Ashton L, Borrow R, Goldblatt D, Andrews N, et al. Effects of prior polysaccharide vaccination on magnitude, duration, and quality of immune responses to and safety profile of a meningococcal serogroup C tetanus toxoid conjugate vaccination in adults. Clin Diagn Lab Immunol 2004;11:1100–4. [19] Musher DM, Ceasar H, Kojic EM, Musher BL, Gathe JC, RomeroSteiner S, et al. Administration of protein-conjugate pneumococcal vaccine to patients who have invasive disease after splenectomy despite their having received 23-valent pneumococcal polysaccharide vaccine. J Infect Dis 2005;191:1063–7. [20] Bogaert D, Hermans PW, Adrian PV, R¨umke HC, de Groot R. Pneumococcal vaccines: an update on current strategies. Vaccine 2004;22:2209–20. [21] Tai SS. Streptococcus pneumoniae protein vaccine candidates: properties, activities and animal studies. Crit Rev Microbiol 2006;32:139– 53. [22] Scott DA, Komjathy SF, Ruckle J, Supan L, dar M, Baker S, et al. Safety and immunogenicity of the 13-valent pneumococcal conjugate vaccine in healthy adults. Proceedings of the fifth international symposium on pneumococci and pneumococcal diseases, Alice Springs, Central Australia, 2–6 April 2006, 255 pp. [23] Schuerman L, Prymula R, Henckaerts I, Poolman J. ELISA IgG concentrations and opsonophagocytic activity following pneumococcal protein D conjugate vaccination and relationship to efficacy against acute otitis media. Vaccine 2007;25:1962–8.
The 23-valent pneumococcal polysaccharide vaccine does not provide additional serotype antibody protection in children who have been primed with two doses of heptavalent pneumococcal conjugate vaccine Paul Balmer a , Ray Borrow a , Peter D. Arkwright b,∗ a
Health Protection Agency, Clinical Sciences Building II, Manchester Royal Infirmary, Oxford Road, Manchester M13 9WL, United Kingdom b University of Manchester, Booth Hall Children’s Hospital, Charlestown Road, Manchester M9 7AA, United Kingdom Received 14 April 2007; received in revised form 4 June 2007; accepted 11 June 2007 Available online 29 June 2007
Abstract Current guidelines recommend up to two doses of the pneumococcal conjugate heptavalent vaccine (PCV-7) in children up to 5 years old followed by and a dose of the polysaccharide vaccine (PPV-23) for patients over 2 years old to broaden serotype immunity. We assessed the serotype responses to two doses of PCV-7 and a dose of PPV-23 in a cohort of children in the 2–16-year age range in order to determine whether PPV-23 induced effective immunity to non-PCV-7 serotypes. Pneumococcal antibody concentrations to the seven serotypes covered by PCV-7 and five additional serotypes covered by PPV-23 but not PCV-7 were measured in 60 children aged 2–16 years. None of the children had a primary antibody immunodeficiency. Vaccinated children had 7–30-fold higher antibody concentrations than unvaccinated children to all serotypes contained in the PCV-7 (P < 0.001). In contrast, serotypes covered by the PPV-23 but not PCV-7 were only one- to two-fold higher and there was no significant increase in the number of children who had protective concentrations of antibody (≥0.35 mcg/ml) against these serotypes. In this cohort of children, PPV-23 vaccine did not broaden the protection in vitro against potentially pathogenic strains of Streptococcus pneumoniae. We call into question the recommendation to use the PPV-23 in children. © 2007 Elsevier Ltd. All rights reserved. Keywords: Streptococcus pneumoniae; Pneumococcal antibodies; Serotypes; Vaccine; Children
1. Introduction Invasive pneumococcal disease leads to significant morbidity and mortality in both children and adults [1,2]. In children in England and Wales, 80% of invasive infections are caused by 8–10 capsular strains [3]. The heptavalent pneumococcal conjugate vaccine (PCV-7) was introduced into the UK in 2002 for at risk groups under 2 years old. From 2006 it has been included into the routine infant vaccination schedule. For children and adults in certain clinical risk groups, for example patients with chronic respiratory, renal or liver disease, congenital heart disease, patients with cochlear implants ∗
Corresponding author. Tel.: +44 161 918 5112; fax: +44 161 918 5143. E-mail address: peter [email protected] (P.D. Arkwright).
0264-410X/$ – see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.vaccine.2007.06.021
and patients with no functioning spleen, up to two doses of PCV-7 are recommended in children under 5 years old, followed by a dose of pneumococcal polysaccharide vaccine (PPV-23) for any patient over 2 years old to broaden protection against serotypes not covered by the PCV-7 vaccine [4]. The PCV-7 has been shown to provide excellent protection against invasive pneumococcal disease including pneumonia caused by the seven serotypes covered by the vaccine [5–7]. In contrast, it is difficult to reach firm conclusions about the clinical effectiveness of PPV-23, which seems to be around 50–70% effective in terms of preventing pneumococcal bacteraemia. There is no evidence that this vaccine prevents non-bacteraemic pneumococcal pneumonia or otitis media, or reduces mortality from pneumococcal infection [8–11].
6322
P. Balmer et al. / Vaccine 25 (2007) 6321–6325
In a previous study, we showed that after vaccination of children with two doses of PCV-7 followed by a dose of PPV-23, there was significant increases in the concentration in all serotypes covered by PCV-7, but no change in the concentration of two pneumococcal serotypes (1 and 5) covered by PPV-23 but not PCV-7 [12]. These data called into question the immunogenicity of PPV-23, at least in children aged 2–16 years old. In this study we extend and consolidate these findings by examining the differences in 12 serotype concentrations, 7 covered by PCV-7 and 5 only covered by PPV-23 after vaccination with 2 doses of PCV-7 followed by a dose of PPV-23. The study shows a clear lack of immunogenicity of the PPV-23, and an inability of this vaccine to broaden the protection of children against potentially pathogenic pneumococcal serotypes in children.
2. Materials and methods 2.1. Patients Patients for inclusion in the study were identified from a database of stored serum samples, which had been received between August 2002 and August 2005 by the Vaccine Evaluation Unit, North West HPA Regional Laboratory in Manchester. Limited pneumococcal serotype responses (seven PCV-7 serotypes as well as serotypes 1 and 5) had previously been performed on these samples, but were repeated with the additional analysis of a further three non-PCV-7 serotypes (serotypes 2, 7F, and 19A). Only children aged 16 years or less (median age 5 years) for whom detailed hospital records were available for review were included in the analysis. All patients had been referred to a single paediatric immunology clinic with a history of symptoms of respiratory infections. Patients with underlying primary antibody deficiencies (defined as those with serum immunoglobulin concentrations below the normal age-related ranges and non-protective responses post-tetanus and Haemophilus influenzae type b vaccination) were excluded. At the time of analysis, 97% of patients had been discharged from followup. Pneumococcal antibody levels were available on 37 children prior to any pneumococcal vaccination and on 27 after vaccination, which in all cases had involved giving two doses of the PCV-7 (Prevenar, Wyeth Pharmaceuticals, Herts, United Kingdom) and then one dose of PPV-23 (Pneumovax II, Pasteur Merieux MSD Ltd. Herts, United Kingdom) at monthly intervals. Blood for antibody measurements were taken at a median (inter-quartile range) time of 2 (1–4) months after the final PPV-23 vaccine. Only in 4 of the 60 children were paired pre- and post-vaccination samples available for analysis. Age (median (inter-quartile range) 5 (3–10) years versus 6 (3–10) years; P = 1.0), gender (57% males versus 48% males, P = 0.5) and ethic background (89% Caucasian versus 92% Caucasian, P = 1.0) distributions of the pre- and post-vaccination groups were not statistically different. The research project was granted ethics approval by the local
research ethics committee and consent was obtained from parents of all patients. There was no external funding for this study. 2.2. Multiplex fluorescent bead assay for the quantitative detection of serum IgG antibodies to Streptococcus pneumoniae capsular polysaccharides Twelve different pneumococcal serotype concentrations (1, 3, 4, 5, 6B, 7F, 9V, 14, 18C, 19A, 19F, 23F) were assayed by a two-step procedure as previously described [13,14]. Pneumococcal polysaccharide antigens were initially conjugated to microspheres. The polysaccharide is coupled to poly-l-lysine and conjugated to the microspheres by a twostep carbodiimide reaction using EDC with sulpho-NHS and cyanuric chloride and purified down a Sephadex column. The assays were performed in 96-well microtitre filter plates using 25 l of the standards and diluted samples. As the patient’s samples were diluted at 1 in 100 only 5 l of sera was required for the assays. A double adsorption step of sera with both C-Ps and type 22F pneumococcal polysaccharide was performed. This was, followed by the addition of 5000 beads/region/25 l, and then 100 l of 1:200 dilution of R-phycoerythrin conjugated anti-human IgG (Jackson ImmunoResearch Lab, West Grove, USA) in PBS (binding all IgG subclasses) with 20 min incubations. Assays were done in duplicate and read using a Bioplex protein array system (Bio-Rad, Herts, United Kingdom). Results were reported as individual IgG antibody concentrations (g/ml) to each of the 12 pneumococcal serotypes in the assay. A serum pneumococcal serotype concentration ≥0.35 g/ml is now suggested as providing adequate protection against pneumococcal infection in infants [15,16]. 2.3. Statistical analysis Data were analysed using SPSS 12.0 software package (SPSS Inc., Chicago, USA). As much of the data was found not to be normally distributed non-parametric statistics were used throughout. Medians (inter-quartile ranges) are quoted for continuous variables. The Mann–Whitney U-test was used to check for statistical differences between these data groups. Chi-square statistic was used for discrete data. Because of the number of comparisons, differences between groups were documented as being significant only if P values were <0.01.
3. Results 3.1. Demographic and clinical characteristics of study cohort Sixty children aged 2–16 years (median 5 years) of whom 30 (50%) were male were included in the study. Twenty-five (42%) patients had a history of respiratory infections, 2 (3%)
P. Balmer et al. / Vaccine 25 (2007) 6321–6325
6323
Fig. 1. Box-plots showing pneumococcal serotype concentrations in children who have not been vaccinated against Streptococcus pneumoniae (unfilled boxes) and those that have had two doses of PCV-7 followed by a dose of PPV-23 (hatched boxes). Median (thick bar) and quartiles (box). Serotypes with asterisks are covered by PCV-7. **P < 0.001 by Mann–Whitney U-test, other comparisons were not statistically different.
a history of meningococcemia, but in the remainder there was no specific clinical indication within the hospital records for why the pneumococcal antibody test had been requested. Fifty-eight (97%) of children had been discharged from further follow-up. There was no evidence from measurement of serum immunoglobulins and specific antibodies to other vaccines (tetanus and Haemophilus influenzae, type b) of an underlying antibody immunodeficiency. 3.2. Pneumococcal serotype-specific concentrations in unvaccinated children and after two doses of PCV-7 followed by a dose of PPV-23 Pneumococcal serotype-specific IgG covered (serotypes 4, 6B, 9V, 14, 18C, 19F and 23F) and not covered (serotype 1, 3, 5, 7F and 19A) by PCV-7 were studied. In vaccinated children concentrations of serotypes covered by the PCV-7 vaccine were 7–30-fold higher, in contrast to concentrations of serotypes covered by the PPV-23 but not the PCV-7 vaccine
which were only one- to two-fold higher than in unvaccinated children (Fig. 1). Natural protection (defined as serotype concentrations ≥0.35 g/ml) in unvaccinated children ranged from 11% of children for pneumococcal serotype 6B to 65% of children for serotype 3, indicating variation in environmental exposure to these potential pathogens (Table 1). After pneumococcal vaccination, protection against serotypes covered by the PCV-7 vaccine was significantly enhanced to between 82 and 100%. In contrast, there was no significant difference in the percentage of children protected against serotypes covered by the PPV-23 but not PCV-7 vaccine, where levels of protection remained at between 44 and 82%. 3.3. Effect of age on children’s response to vaccination There was no significant correlation between the age of the child and the post-vaccination concentrations of any of the 12 serotypes studied, as measured using Spearman correlation
6324
P. Balmer et al. / Vaccine 25 (2007) 6321–6325
Table 1 Proportion of children with pneumococcal serotype concentrations ≥0.35 g/ml n Age (years) Males (%) P1 P3 P5 P7F P19A P4* P6B* P9V* P14* P18* P19F* P23F*
No vaccination
Post-vaccine
P value
37 5 (3–10) 21 (57) 13 (35) 24 (65) 14 (38) 15 (40) 14 (38) 7 (19) 4 (11) 14 (38) 19 (51) 8 (22) 14 (51) 13 (35)
27 6 (3–10) 13 (48) 13 (48) 22 (82) 12 (44) 14 (52) 14 (52) 23 (85) 22 (82) 24 (89) 26 (96) 27 (100) 23 (85) 23 (85)
1.0 0.6 0.6 0.2 0.6 0.5 0.3 0.0001 0.0001 0.0001 0.0001 0.0001 0.01 0.0001
Table compares children who have never had any pneumococcal vaccinations with those who have been vaccinated with two doses of PCV-7 followed by a dose of PPV-23. Age is given in median (inter-quartile range). Data for serotype are given as number (percentage) with antibody concentrations ≥0.35 g/ml. Serotypes with asterisk are those covered by PCV-7. P value is calculated using Chi-square analysis.
coefficient or comparing groups of children aged 2–5 years old and children aged 6–16 years old (data not shown). There were no significant age or gender differences between the preand post-vaccination groups (Table 1).
4. Discussion This study clearly shows the lack of in vitro immunogenicity of the PPV-23 vaccine in children, when compared with the excellent pneumococcal serotype responses to the conjugate vaccine PCV-7. These data complement the clinical data from three metaanalyses, which showed that the PPV-23 vaccine offers little or no protection against pneumonia or death from S. pneumoniae in adults, but may have some protective effect against invasive disease in the elderly, particularly those with higher risk of this infection [9–11]. Although the numbers in the study are small, the data are highly significant and there are clear differences between serotype responses to PCV-7 and PPV-23. PCV-7 is known to stimulate an IgG1 subclass response while PPV-23 stimulates an IgG2 subclass response [12,17]. The multiplex assay detects both IgG1 and IgG2 antibodies and therefore the differences in vaccine efficacy cannot be put down to restricted measurement of one but not another immunoglobulin subclass. Our previous study demonstrated that the antibody response to Prevenar in children is IgG1 subclass specific [12]. The study is limited to analysis of sera samples available in the Vaccine Evaluation Unit in Manchester prior to addition of PCV-7 to the infant national vaccination schedule in 2006. Ideally paired pre- and post-vaccination sera should have been studied, but unfortunately these were only avail-
able from 4 of the 60 children. The pre- and post-vaccination groups were however comparable for age, gender and ethnic origin. The group of children studied here was considered at “higher risk” of infection with S. pneumoniae infections based on the history of recurrent respiratory infections, even though specific underlying antibody immunodeficiency disorders were not found in any of the children and 97% were discharged from further follow-up. This cohort would therefore seem a more appropriate study group in order to test the current pneumococcal vaccination guidelines for “high risk” groups. The results presented may however not predict the pneumococcal responses of a “health cohort” of children from the general population. In summary, there is no evidence from this study to support the current recommendations made by expert opinion in the latest edition of immunisation against infectious disease [4] for the addition of PPV-23 to the vaccination schedule for children in “clinical risk groups”. There is some suggestion that prior administration of meningococcal polysaccharide vaccines may interfere with the response to subsequent meningococcal conjugate vaccines [18], although this may not be the case for pneumococcal vaccines [19]. Thus although the PPV-23 vaccine may of limited efficacy, it does not seem to do any harm. The question that now needs to be addressed is that with the introduction of PCV-7 into routine use and the likely introduction of further multi-conjugate pneumococcal vaccines onto the market in the next few years (PCV-13 and PCV-10) [20–23], is there any role for the PPV23 in children. Based on the data presented, our personal recommendations are that (1) PCV-7 should replace PPV-23 for all high risk children, not just those less than 5 years old, requiring immunisation against community acquired S. pneumoniae and (2) the use of PPV-23 as an additional booster following PCV-7 should be discontinued or at least be reevaluated.
Acknowledgement We would like to acknowledge Michael Wilding for immunoassay performance. Conflict of interest statement: Dr. Balmer has received assistance to attend scientific meetings from Wyeth Vaccines, Baxter Bioscience and Chiron Vaccines. Industry honoraria received for lecturing are paid directly into Central Manchester and Manchester Children’s University Hospitals NHS Trust endowment fund. Dr. Borrow has received assistance to attend scientific meetings from Wyeth Vaccines and Baxter Bioscience and has served as a consultant for GlaxoSmithKline, Fujisawa GmbH, Sanofi Pasteur and Baxter Bioscience. Industry honoraria received for consulting, lecturing and writing are paid directly into Central Manchester and Manchester Children’s University Hospitals NHS Trust endowment fund. Dr. Borrow has performed contract research on behalf of the Health Protection Agency (funded by Wyeth Vaccines, Chiron Vaccines, Baxter Bioscience,
P. Balmer et al. / Vaccine 25 (2007) 6321–6325
GlaxoSmithKline, Sanofi Pasteur, Fujisawa GmbH, Alexion Pharmaceuticals Inc., Microscience Ltd. and Xenova Research Ltd. Dr. Arkwright declares no conflicts of interest.
References [1] Williams BG, Gouws E, Boschi-Pinto C, Bryce J, Dye C. Estimates of world-wide distributions of child deaths from acute respiratory infections. Lancet Infect Dis 2002;2:25–32. [2] Fedson DS, Scott JA. The burden of pneumococcal disease among adults in developed and developing countries: what is and is not known. Vaccine 1999;17(Suppl 1):S11–8. [3] www.hpa.org.uk/infections/topics az/pneumococcal/. [4] Immunisation against infectious disease “The Green Book”. In: Salsbury D, Ramsay M, Noakes K, editors. Department of Health, U.K. TSO 2006 Third Edition. www.dh.gov.uk/PolicyAndGuidance/HealthAndSocialCareTopics/GreenBook/GreenBookGeneralInformation/ GreenBookGeneralArticle/fs/en?CONTENT ID=4097254&chk =isTfGX. [5] Black S, Shinefield H, Fireman B, Lewis E, Ray P, Hansen JR, et al. Efficacy, safety, and immunogenicity of heptavalent pneumococcal conjugate vaccine in children. Pediatr Infect Dis J 2000;19:187–95. [6] Black S, Shinefield HR, Ling S, Hansen J, Fireman B, Spring D, et al. Effectiveness of heptavalent pneumococcal conjugate vaccine in children younger than 5 years of age for prevention of pneumonia. Pediatr Infect Dis J 2002;21:810–5. [7] Black S, Shinefield H, Baxter R, Austrian R, Elvin L, Hansen J, et al. Impact of the use of heptavalent pneumococcal conjugate vaccine on disease epidemiology in children and adults. Vaccine 2006;24(Suppl 2):S2–80. [8] Butler JC, Breiman RF, Campbell JF, Lipman HB, Broome CV, Facklam RR. Pneumococcal polysaccharide vaccine efficacy. An evaluation of current recommendations. JAMA 1993;270:1826–31. [9] Dear K, Holden J, Andrews R, Tatham D. Vaccines for preventing pneumococcal infection in adults. Cochrane Database Syst Rev 2003;4. CD000422. [10] Mangtani P, Cutts F, Hall AJ. Efficacy of polysaccharide pneumococcal vaccine in adults in more developed countries: the state of the evidence. Lancet Infect Dis 2003;3:71–8. [11] Melegaro A, Edmunds WJ. The 23-valent pneumococcal polysaccharide vaccine. Part I. Efficacy of PPV in the elderly: a comparison of meta-analyses. Eur J Epidemiol 2004;19:353–63.
6325
[12] Uddin S, Borrow R, Haeney MR, Moran A, Warrington R, Balmer P, et al. Total and serotype-specific pneumococcal antibody titres in children with normal and abnormal humoral immunity. Vaccine 2006;24:5637–44. [13] Lal G, Balmer P, Stanford E, Martin S, Warrington R, Borrow R. Development and validation of a nonaplex assay for the simultaneous quantitation of antibodies to nine Streptococcus pneumoniae serotypes. J Immunol Meth 2005;296:135–47. [14] Borrow R, Balmer P. Assessment of functional antibody responses. Meth Mol Med 2003;87:289–300. [15] World Health Organisation. Pneumococcal conjugate vaccines. Recommendations for the production and control of pneumococcal conjugate vaccines. WHO Tech. Rep. Ser. 2005;927:64–98. [16] Siber GR, Chang I, Baker S, Fernsten P, O’Brien KL, Santosham M, et al. Estimating the protective concentration of anti-pneumococcal capsular polysaccharide antibodies. Vaccine 2007 February 21 [Epub ahead of print]. [17] Barrett DJ, Ayoub EM. IgG2 subclass restriction of antibody to pneumococcal polysaccharides. Clin Exp Immunol 1986;63:127–34. [18] Southern J, Deane S, Ashton L, Borrow R, Goldblatt D, Andrews N, et al. Effects of prior polysaccharide vaccination on magnitude, duration, and quality of immune responses to and safety profile of a meningococcal serogroup C tetanus toxoid conjugate vaccination in adults. Clin Diagn Lab Immunol 2004;11:1100–4. [19] Musher DM, Ceasar H, Kojic EM, Musher BL, Gathe JC, RomeroSteiner S, et al. Administration of protein-conjugate pneumococcal vaccine to patients who have invasive disease after splenectomy despite their having received 23-valent pneumococcal polysaccharide vaccine. J Infect Dis 2005;191:1063–7. [20] Bogaert D, Hermans PW, Adrian PV, R¨umke HC, de Groot R. Pneumococcal vaccines: an update on current strategies. Vaccine 2004;22:2209–20. [21] Tai SS. Streptococcus pneumoniae protein vaccine candidates: properties, activities and animal studies. Crit Rev Microbiol 2006;32:139– 53. [22] Scott DA, Komjathy SF, Ruckle J, Supan L, dar M, Baker S, et al. Safety and immunogenicity of the 13-valent pneumococcal conjugate vaccine in healthy adults. Proceedings of the fifth international symposium on pneumococci and pneumococcal diseases, Alice Springs, Central Australia, 2–6 April 2006, 255 pp. [23] Schuerman L, Prymula R, Henckaerts I, Poolman J. ELISA IgG concentrations and opsonophagocytic activity following pneumococcal protein D conjugate vaccination and relationship to efficacy against acute otitis media. Vaccine 2007;25:1962–8.