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Comparison of the reactogenicity and immunogenicity of a split and a subunit-adjuvanted influenza vaccine in elderly subjects
Vaccine 21 (2003) 1268–1274
Comparison of the reactogenicity and immunogenicity of a split and a subunit-adjuvanted influenza vaccine in elderly subjects S. Squarcione a,∗ , S. Sgricia b,1 , L.R. Biasio c,2 , E. Perinetti c,3 a
Direzione Sanitaria—Azienda IRCCS, Ospedale Lazzaro Spallanzani, Via Portuense, 292, 00149 Rome, Italy b Servizio di Vaccinazioni, Via Terme di Traiano, 39/A, 00053 Civitavecchia, Italy c Aventis Pasteur MSD S.p.A., Via degli Aldobrandeschi, 15, 00163 Rome, Italy Received 4 September 2001; received in revised form 25 July 2002; accepted 9 August 2002
Abstract A randomised, open study was carried out among an elderly population in order to compare the reactogenicity and immunogenicity of an inactivated, split virion influenza vaccine (Vaxigrip ® , Aventis Pasteur MSD, Lyon, France) with that of an MF59-adjuvanted, subunit vaccine (Fluad ® , Chiron Vaccines, Siena, Italy). Both vaccines contained the three strains: A/Sydney/5/97 (H3N2), A/Beijing/262/95 (H1N1) and B/Beijing/184/93, recommended by the WHO for the 1998–1999 influenza season. A total of 2150 subjects were vaccinated and included in the reactogenicity analysis. A total of 1076 subjects received Vaxigrip ® (age 73.3 ± 5.9 years, 49.6% men) and 1074 subjects received Fluad ® (age 73.4 ± 5.9 years, 52.3% men). All subjects were kept under medical observation for 30 min after vaccination, in order to check any immediate local and/or systemic reaction. A self monitoring diary card was given to all subjects to collect any local and/or systemic reaction occurring during the 3 days following the vaccination, any adverse event occurring between vaccination day and 21st day post-vaccination and any medication taken during the study period. A total of 1186 subjects were included in the immunogenicity analysis. A total of 591 subjects received Vaxigrip ® (age 73.4 ± 5.6 years, 52.3% men) and 595 subjects received Fluad ® (age 73.8 ± 5.9 years, 55.8% men). Blood samples were collected pre- and 21 days post-vaccination and were analysed by the haemagglutination inhibition assay. In terms of reactogenicity both vaccines were generally well tolerated. The frequency of local reactions was lower in the group that received Vaxigrip ® . Pain at the injection site occurring from 30 min to 3 days after vaccination was also significantly less frequent (P = 0.005) in the Vaxigrip ® group. Fever ≥37.5 ◦ C was reported in less than 1% of all vaccinated subjects. No serious adverse event was related to vaccine administration. In terms of immunogenicity both vaccines induced an effective immune response (anti-HI titre ≥40) against A/Sydney/5/97 (H3N2) and A/Beijing/262/95 (H1N1) strains in the entire population. Vaxigrip ® and Fluad ® induced similar seroprotection and seroconversion rates against the A/Sydney/5/97 (H3N2) strain. For both vaccines a lower percentage of subjects achieved a seroprotective titre ≥40 against the B/Beijing/184/93. A lower antibody response against the influenza B strain was also observed in other studies conducted during the same season. In subjects 75 years of age or older, Fluad ® was more immunogenic than Vaxigrip ® for all three virus strains. © 2002 Elsevier Science Ltd. All rights reserved. Keywords: Influenza; Vaccination; Elderly; Reactogenicity; Immunogenicity
1. Introduction Vaccination is currently the most effective means of controlling influenza and preventing its complications and mortality in persons at risk [1–4]. Following vaccination, seroprotective antibody titres are achieved in a high pro∗
Corresponding author. Tel.: +39-6-5583329; fax: +39-6-5592581. E-mail addresses: [email protected] (S. Squarcione), [email protected] (S. Sgricia), [email protected] (L.R. Biasio), [email protected] (E. Perinetti). 1 Tel.: +39-766-591718/591719; fax: +39-766-599604. 2 Tel.: +39-6-66409227; fax: +39-6-66512539. 3 Tel.: +39-6-66409205; fax: +39-6-66512539.
portion of vaccinated subjects, but in elderly people (≥65 years of age) antibody responses are often lower than those in younger adults [3,5,8,9]. In order to increase the antibody response in groups at risk, adjuvanted and virosomal vaccines have been developed. The administration of an MF59-adjuvanted influenza subunit vaccine (Fluad ® ) has been shown to improve immunogenicity in both animals and man [10,12,13,15]. However, compared with conventional subunit vaccines, this adjuvanted vaccine has caused significantly higher rates of mild and transient local reactions [13,14]. In studies carried out among elderly people, local reactions were observed more frequently in subjects vaccinated with adjuvanted
0264-410X/02/$ – see front matter © 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 2 6 4 - 4 1 0 X ( 0 2 ) 0 0 4 0 1 - 2
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vaccine as opposed to those receiving non-adjuvanted vaccine [11,15,16]. The administration of a conventional split influenza virus vaccine (Vaxigrip ® ) to elderly subjects, young adults and children induces a good immune response and has a good local and systemic safety profile [17–21]. When compared with a subunit influenza vaccine, Vaxigrip ® has been shown to be more immunogenic in persons 17–83 years in age [18]. A prospective study comparing whole virus, subunit and split virus vaccines administered to elderly persons has confirmed the good safety profile of Vaxigrip ® [22]. We report the results of a study comparing the reactogenicity and immunogenicity of Vaxigrip ® with that of a recently developed subunit-adjuvanted vaccine (Fluad ® ) when administered to elderly subjects (≥65 years of age).
investigator, might interfere with the evaluation of the study results. All subjects were observed for 30 min following vaccine administration to check for immediate local and/or systemic reactions. Each subject filled out a diary card and recorded any local and/or systemic reaction occurred during the 3 days following the vaccination, any adverse event occurred between vaccination day and 21st day post-vaccination and any medication taken during the study period. Local reactions included pain, erythema, induration, ecchymosis, oedema, abscess. Systemic reactions included fatigue, malaise, myalgia, arthralgia, shivering, sweating, headache, axillary temperature ≥37.5 ◦ C or aggravation of any pre-existing symptom. On days 0 and 21 (±3 days) 10 ml venous blood samples were obtained from a subset of all subjects.
2. Materials and methods
2.2. Vaccines
2.1. Study design
The two vaccines used in the study were an inactivated, Triton X-100 ® split influenza vaccine—Vaxigrip ® (batch no. P5627, Aventis Pasteur MSD, Lyon, France) and a subunit influenza vaccine adjuvanted with MF59—Fluad ® (batch no. 0521, Chiron Vaccines, Siena, Italy). The MF59 adjuvant is an oil-in-water microemulsion consisting of squalene, polysorbate 80 and sorbitan trioleate [15,16,23]. A single vaccine dose (0.5 ml) contained 15 g of viral haemagglutinin (HA) for each of the three influenza strains: A/Sydney/5/97 (H3N2), A/Beijing/262/95 (H1N1) and B/Beijing/184/93. Both vaccines were supplied in pre-filled syringes and were injected intramuscularly in the deltoid.
The primary objective of this open, randomised, phase IV study was to compare the reactogenicity of local reactions of Vaxigrip ® and Fluad ® , in particular the rates of injection site pain. The secondary objective was to demonstrate the equivalence (non-inferiority) in immunogenicity for both vaccines. The trial was carried out in compliance with Good Clinical Practice in a Public Health Department (AUSL RMF-Civitavecchia, Rome, Italy) during the influenza vaccination campaign for the 1998–1999 influenza season. Written informed consent was obtained from all participants before study participation. Each was randomly assigned to receive either Vaxigrip ® or Fluad ® . All subjects enrolled in the study were ≥65 years in age and in good health. Demographic data for the subjects included are described in Table 1. Exclusion criteria included: febrile illness ≥37.5 ◦ C on the day of enrolment, influenza vaccine administration within the past 6 months, any other vaccination within the past 15 days (30 days if live virus vaccine), any analgesic treatment on the inclusion day, treatment with corticosteroids on a regular basis (except for local corticosteroids), any bleeding disorder, known allergy to egg protein or suspected allergy to any of the vaccine components and any condition which, in the opinion of the Table 1 Demographic characteristics
Reactogenicity population (N) Mean age (years ± S.D.) Men (%) Immunogenicity population (N) Mean age (years ± S.D.) Men (%)
Vaxigrip ®
Fluad ®
1076 73.3 ± 5.9 49.6
1074 73.4 ± 5.9 52.3
591 73.4 ± 5.6 52.3
595 73.8 ± 5.9 55.8
2.3. Antibody studies Anti-haemagglutinin antibody titres to the three influenza virus haemagglutinins were determined using the haemagglutination inhibition test (HI test) [30,31]. The principle of the HI test is based on the ability of specific anti-influenza antibodies to inhibit haemagglutination of chicken red blood cells (RBC) by influenza virus haemagglutinin (HA). The sera to be tested were previously treated to eliminate the non-specific inhibitors and the anti-species haemagglutinin. Titre is expressed as the reciprocal of the highest dilution of serum that completely inhibited hæmagglutination. A level of 10 or below was regarded as undetectable. For evaluation purposes, a titre value <10 was considered as equal to 5. A titre of 40 was considered as protective. Anti-HI titres to B/Beijing/184/93 were measured using B/Harbin/7/94. The immunogenicity of the two study vaccines was assessed according to the frequency of seroconversion on day 21, the proportion of subjects seroprotected on days 0 and 21 and the increase in geometric mean titre of anti-HI between days 0 and 21, defined as the geometric mean titre ratio (GMTR). Seroconversion was defined as a change from a pre-vaccination titre <10 to a post-vaccination titre ≥40 or a four-fold or greater rise in
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Table 2 Local and systemic reactions Vaxigrip ® (N = 1076)
Any reaction (local or systemic)
Fluad ® (N = 1074)
P value
No. of subjects
Percentage
No. of subjects
Percentage
143
13.3
168
15.6
Any immediate reaction (within 30 min) Any immediate local reaction Any immediate systemic reaction
8 8 –
0.7 0.7 0.0
13 7 6
1.2 0.7 0.6
– 1.000 0.015
Any delayed reaction (30 min to 3 days) Any local reaction Pain at the injection site Any systemic reaction
141 93 42 65
13.1 8.6 3.9 6.0
160 114 71 70
14.9 10.6 6.6 6.5
– 0.125 0.005 0.658
titre in those with an initial anti-HI titre ≥10 [32]. Seroprotection was defined as a titre≥40.
–
the two groups (5% for Vaxigrip ® and 3.8% for Fluad ® ). Only one subject in the Vaxigrip ® group received high doses of corticosteroids.
2.4. Sample size and statistical analysis 3.1. Reactogenicity Reactogenicity: the percentages of local and systemic reactions in the Vaxigrip ® and Fluad ® groups were compared using Fisher’s exact test. The study was based on the hypothesis that Vaxigrip ® and Fluad ® would produce pain at the injection site in the same percentage of subjects. Assuming that the percentages were 12% in the Vaxigrip ® group, and 17% in the Fluad ® group, 1037 subjects per group would have to be analysed to show a significant difference with an α of 5% and a power of 90% in a two-sided test Table 2. Immunogenicity: seroprotection and seroconversion rates for both vaccines were compared using the equivalence (non-inferiority) testing approach, with a one-sided α of 2.5% and a clinically acceptable difference of 10%. All enrolled subjects were included in the reactogenicity analysis. Subjects excluded from the immunogenicity analysis were those non-compliant with the immunisation, blood sampling schedule or those who received medication that could interfere with the immune response.
The overall rates of immediate local reactions (occurring 0–30 min after vaccine administration) were similar for the two groups. Pain at the injection site was observed in 0.1% of Vaxigrip ® subjects (mild) and 0.3% of Fluad ® subjects (mild or moderate). None of the six immediate systemic reactions in the Fluad ® group were serious. The frequency of local and systemic reactions occurring from 30 min to 3 days after vaccination was also low in both groups. There was a statistically significantly lower rate of injection site pain in the Vaxigrip ® group (3.9%) compared with the Fluad ® group (6.6%) (P = 0.005). Other local reactions consisted mainly of erythema and induration. Systemic reactions were less frequent in the Vaxigrip ® group compared with the Fluad ® group (any systemic reaction: 6.0 and 6.5%, respectively). The intensity of most systemic reactions was also mild for both vaccines. Fever ≥37.5 ◦ C was reported in fewer than 1% of vaccinees. None of the nine serious adverse events (SAEs) were considered to be related to either of the study vaccines.
3. Results
3.2. Immunogenicity
A total of 2150 subjects were vaccinated, of these 1076 received Vaxigrip ® and 1074 Fluad ® . The two vaccine groups were similar with respect to demographic characteristics (Table 1). A total of 1186 paired blood specimens (days 0 and 21) were obtained for antibody assessment. Among the 1186 included in the immunogenicity analysis, 591 received Vaxigrip ® and 595 Fluad ® . Of the total study population, 81 subjects (3.8%) withdrew prematurely: 40 (1.86%) in the Vaxigrip ® group and 41 (1.90%) in the Fluad ® group. The majority of premature withdrawals were due to “lost to follow-up”. The number of subjects taking concomitant medications (analgesics, antipyretics and/or corticosteroids) was low and similar among
Paired blood specimens (days 0 and 21) were obtained from 1186 subjects; 591 in the Vaxigrip ® group and 595 in the Fluad ® group. Both vaccines induced increases in anti-HI antibody titres ≥40 (seroprotective titre) in a large proportion of subjects (Table 3; Figs. 1–3). In both groups, more subjects achieved seroprotective titres (≥40) against the A/Sydney/5/97 (H3N2) and A/Beijing/262/95 (H1N1) strains than against the B/Beijing/184/93 strain. Vaxigrip ® was shown to be equivalent (non-inferiority) to Fluad ® regarding seroprotection and seroconversion rates against the A/Sydney/5/97 (H3N2) strain (Table 3, Fig. 1). Furthermore, the geometric mean of titre ratios (GMTR; Table 3) confirmed that the two vaccines were similarly
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Table 3 Geometric mean titres for anti-HI antibodies and seroprotection and seroconversion rates in subjects <75 and ≥75 years in age and in the whole population Vaxigrip ® (N = 591)
Fluad ® (N = 595)
A/Sydney/5/97 (H3N2)
A/Beijing/262/95 (H1N1)
B/Beijing/184/93a
A/Sydney/5/97 (H3N2)
A/Beijing/262/95 (H1N1)
B/Beijing/184/93a
36.8 183.2 5.0
10.4 87.1 8.4
9.2 18.9 2.1
39.9 214.3 5.4
11.3 154.4 13.7
9.3 24.0 2.6
<75 years ≥75 years Whole population
92.4 87.1 90.4
74.9 66.1 71.6
30.9 27.4 29.5
93.8 94.2 94.0
86.4 78.9 83.4
37.7 38.4 38.0
Seroconversiond (%) <75 years ≥75 years Whole population
61.9 58.0 60.4
66.9 59.5 63.7
15.6 12.6 14.5
59.8 62.4 60.8
77.9 73.1 76.0
25.2 17.8 22.2
Pre-GMT ( day 0) Post-GMT (day 21) GMTRb Seroprotectionc (%)
a
Anti-HI antibodies to B/Beijing/184/93 were assessed using B/Harbin/7/94. Geometric mean of anti-HI titre ratio (post/pre). c Anti-HI titre ≥40 on day 21. d Greater than or equal to four-fold rise in anti-HI titre between days 0 and 21. b
Fig. 1. Reverse cumulative distribution curves (RCDs) of the anti-HI titres for the A/Sydney/5/97 (H3N2) strain. The titres are expressed as log10 titres, not as two-fold dilutions (10, 20, 40, etc.).
immunogenic against the A/Sydney/5/97 (H3N2) strain. However, Fluad ® elicited greater increases in GMTRs against the other two strains (A/Beijing/262/95 (H1N1) and B/Beijing/184/93). Seroprotection and seroconversion rates for the two vaccines were also separately assessed in subjects <75 or ≥75 years of age (Table 3). The seroprotection and seroconversion responses to Fluad ® and Vaxigrip ® were similar for the A/Sydney/5/97 (H3N2) strain, in the <75 years of age group. Regarding the other two virus strains, responses were higher in the Fluad ® group. In subjects 75 years of age or
older, Fluad ® was more immunogenic than Vaxigrip ® for all three virus strains.
4. Discussion The safety and effectiveness of inactivated influenza vaccination for elderly people has been demonstrated in several clinical studies [1–9]. Studies carried out among elderly persons in the US and Canada have demonstrated that vaccination prevents approximately 30–50% of deaths
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Fig. 2. Reverse cumulative distribution curves (RCDs) of the anti-HI titres for the A/Beijing/262/95 (H1N1) strain. The titres are expressed as log10 titres, not as two-fold dilutions (10, 20, 40, etc.).
and hospitalisations for influenza-associated respiratory complications [6]. During influenza epidemics, vaccination yields substantial savings in health care costs [7]. The relationship between of anti-HI antibody responses and the clinical efficacy of influenza vaccines is still disputed [24–29]. However, as a surrogate marker for protection, an increase in anti-HI antibody titre has been regularly considered an acceptable measure for evaluating influenza vaccines. For regulatory purposes, anti-HI titres are the basis for the yearly approval of new influenza vaccines. Safety considerations are also important, and can affect acceptance
of influenza vaccines by decision makers responsible for public health programs. In this study, both Vaxigrip ® and Fluad ® were well tolerated. Few local and systemic adverse reactions were observed within 3 days of vaccine administration, although local reactions were slightly more frequent in the Fluad ® group. Vaxigrip ® caused pain at the injection site in a significantly lower proportion of subjects (3.9% for Vaxigrip ® versus 6.6% for Fluad ® ). For both vaccines the intensity of pain was considered mild in most subjects and did not interfere with usual activity.
Fig. 3. Reverse cumulative distribution curves (RCDs) of the anti-HI titres for the B/Beijing/184/93 strain. The titres are expressed as log10 titres, not as two-fold dilutions (10, 20, 40, etc.).
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Systemic adverse reactions after influenza vaccination occurred in low frequencies, as previously observed [21,22]. Fever was reported in a very small percentage of subjects in both groups. Few subjects took antipyretics, analgesics or anti-inflammatory medications following vaccination, another marker of good tolerability. Both vaccines induced good immune responses. Three weeks after vaccination, seroprotection rates were above 60% and seroconversion rates above 30% for the two influenza A strains. Increases in GMT between days 0 and 21 were above 2 for all strains for both vaccines. Significantly, Vaxigrip ® was equivalent to Fluad ® with respect to seroprotection and seroconversion rates against the more virulent A/Sydney/5/97 (H3N2) strain. For subjects ≥75 years in age, Fluad ® was more immunogenic against all three virus strains. Both vaccines produced an increase in the number of subjects protected (titre ≥40) against the A/Sydney/5/97 (H3N2) and A/Beijing/262/95 (H1N1) strains, whereas a lower percentage of subjects achieved a seroprotective titre against the B/Beijing/184/93 strain. A lower antibody response against the influenza B strain was also observed in other studies conducted during the same season [29]. Our findings concerning the reactogenicity and the immunogenicity of Vaxigrip ® and Fluad ® agree with those of other clinical trials [10,15,16]. The feasibility of improving the immunogenicity of conventional influenza vaccines by means of adjuvants (particularly MF59) has been confirmed. This finding is significant with regards to elderly subjects and subjects with chronic diseases. Many of them develop lower antibody responses to conventional inactivated influenza vaccines, in comparison to younger adults. However, the increased immunogenicity of adjuvanted vaccines is associated with a slightly higher frequency of local reactions compared to the conventional vaccine. Thus, it may be preferable to administer adjuvanted influenza vaccines in elderly people and use conventional vaccines in younger subjects.
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[29] Aventis Pasteur. Clinical report on immunogenicty and safety of the inactivated influenza vaccine (split virion) 1998–1999 formulation— A 146 IVB1/GRT 09298. Data on file. [30] Palmer DF, Dowle WR, Coleman MT, Schild GC. Advanced laboratory technicals for immunological diagnostic. US Department of Health Education and Welfare, P.H.S. Atlanta, Immunology Series No. 6. Procedural guide. Part 2. Haemagglutination-inhibition test. 1975. p. 25–62.
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Comparison of the reactogenicity and immunogenicity of a split and a subunit-adjuvanted influenza vaccine in elderly subjects S. Squarcione a,∗ , S. Sgricia b,1 , L.R. Biasio c,2 , E. Perinetti c,3 a
Direzione Sanitaria—Azienda IRCCS, Ospedale Lazzaro Spallanzani, Via Portuense, 292, 00149 Rome, Italy b Servizio di Vaccinazioni, Via Terme di Traiano, 39/A, 00053 Civitavecchia, Italy c Aventis Pasteur MSD S.p.A., Via degli Aldobrandeschi, 15, 00163 Rome, Italy Received 4 September 2001; received in revised form 25 July 2002; accepted 9 August 2002
Abstract A randomised, open study was carried out among an elderly population in order to compare the reactogenicity and immunogenicity of an inactivated, split virion influenza vaccine (Vaxigrip ® , Aventis Pasteur MSD, Lyon, France) with that of an MF59-adjuvanted, subunit vaccine (Fluad ® , Chiron Vaccines, Siena, Italy). Both vaccines contained the three strains: A/Sydney/5/97 (H3N2), A/Beijing/262/95 (H1N1) and B/Beijing/184/93, recommended by the WHO for the 1998–1999 influenza season. A total of 2150 subjects were vaccinated and included in the reactogenicity analysis. A total of 1076 subjects received Vaxigrip ® (age 73.3 ± 5.9 years, 49.6% men) and 1074 subjects received Fluad ® (age 73.4 ± 5.9 years, 52.3% men). All subjects were kept under medical observation for 30 min after vaccination, in order to check any immediate local and/or systemic reaction. A self monitoring diary card was given to all subjects to collect any local and/or systemic reaction occurring during the 3 days following the vaccination, any adverse event occurring between vaccination day and 21st day post-vaccination and any medication taken during the study period. A total of 1186 subjects were included in the immunogenicity analysis. A total of 591 subjects received Vaxigrip ® (age 73.4 ± 5.6 years, 52.3% men) and 595 subjects received Fluad ® (age 73.8 ± 5.9 years, 55.8% men). Blood samples were collected pre- and 21 days post-vaccination and were analysed by the haemagglutination inhibition assay. In terms of reactogenicity both vaccines were generally well tolerated. The frequency of local reactions was lower in the group that received Vaxigrip ® . Pain at the injection site occurring from 30 min to 3 days after vaccination was also significantly less frequent (P = 0.005) in the Vaxigrip ® group. Fever ≥37.5 ◦ C was reported in less than 1% of all vaccinated subjects. No serious adverse event was related to vaccine administration. In terms of immunogenicity both vaccines induced an effective immune response (anti-HI titre ≥40) against A/Sydney/5/97 (H3N2) and A/Beijing/262/95 (H1N1) strains in the entire population. Vaxigrip ® and Fluad ® induced similar seroprotection and seroconversion rates against the A/Sydney/5/97 (H3N2) strain. For both vaccines a lower percentage of subjects achieved a seroprotective titre ≥40 against the B/Beijing/184/93. A lower antibody response against the influenza B strain was also observed in other studies conducted during the same season. In subjects 75 years of age or older, Fluad ® was more immunogenic than Vaxigrip ® for all three virus strains. © 2002 Elsevier Science Ltd. All rights reserved. Keywords: Influenza; Vaccination; Elderly; Reactogenicity; Immunogenicity
1. Introduction Vaccination is currently the most effective means of controlling influenza and preventing its complications and mortality in persons at risk [1–4]. Following vaccination, seroprotective antibody titres are achieved in a high pro∗
Corresponding author. Tel.: +39-6-5583329; fax: +39-6-5592581. E-mail addresses: [email protected] (S. Squarcione), [email protected] (S. Sgricia), [email protected] (L.R. Biasio), [email protected] (E. Perinetti). 1 Tel.: +39-766-591718/591719; fax: +39-766-599604. 2 Tel.: +39-6-66409227; fax: +39-6-66512539. 3 Tel.: +39-6-66409205; fax: +39-6-66512539.
portion of vaccinated subjects, but in elderly people (≥65 years of age) antibody responses are often lower than those in younger adults [3,5,8,9]. In order to increase the antibody response in groups at risk, adjuvanted and virosomal vaccines have been developed. The administration of an MF59-adjuvanted influenza subunit vaccine (Fluad ® ) has been shown to improve immunogenicity in both animals and man [10,12,13,15]. However, compared with conventional subunit vaccines, this adjuvanted vaccine has caused significantly higher rates of mild and transient local reactions [13,14]. In studies carried out among elderly people, local reactions were observed more frequently in subjects vaccinated with adjuvanted
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vaccine as opposed to those receiving non-adjuvanted vaccine [11,15,16]. The administration of a conventional split influenza virus vaccine (Vaxigrip ® ) to elderly subjects, young adults and children induces a good immune response and has a good local and systemic safety profile [17–21]. When compared with a subunit influenza vaccine, Vaxigrip ® has been shown to be more immunogenic in persons 17–83 years in age [18]. A prospective study comparing whole virus, subunit and split virus vaccines administered to elderly persons has confirmed the good safety profile of Vaxigrip ® [22]. We report the results of a study comparing the reactogenicity and immunogenicity of Vaxigrip ® with that of a recently developed subunit-adjuvanted vaccine (Fluad ® ) when administered to elderly subjects (≥65 years of age).
investigator, might interfere with the evaluation of the study results. All subjects were observed for 30 min following vaccine administration to check for immediate local and/or systemic reactions. Each subject filled out a diary card and recorded any local and/or systemic reaction occurred during the 3 days following the vaccination, any adverse event occurred between vaccination day and 21st day post-vaccination and any medication taken during the study period. Local reactions included pain, erythema, induration, ecchymosis, oedema, abscess. Systemic reactions included fatigue, malaise, myalgia, arthralgia, shivering, sweating, headache, axillary temperature ≥37.5 ◦ C or aggravation of any pre-existing symptom. On days 0 and 21 (±3 days) 10 ml venous blood samples were obtained from a subset of all subjects.
2. Materials and methods
2.2. Vaccines
2.1. Study design
The two vaccines used in the study were an inactivated, Triton X-100 ® split influenza vaccine—Vaxigrip ® (batch no. P5627, Aventis Pasteur MSD, Lyon, France) and a subunit influenza vaccine adjuvanted with MF59—Fluad ® (batch no. 0521, Chiron Vaccines, Siena, Italy). The MF59 adjuvant is an oil-in-water microemulsion consisting of squalene, polysorbate 80 and sorbitan trioleate [15,16,23]. A single vaccine dose (0.5 ml) contained 15 g of viral haemagglutinin (HA) for each of the three influenza strains: A/Sydney/5/97 (H3N2), A/Beijing/262/95 (H1N1) and B/Beijing/184/93. Both vaccines were supplied in pre-filled syringes and were injected intramuscularly in the deltoid.
The primary objective of this open, randomised, phase IV study was to compare the reactogenicity of local reactions of Vaxigrip ® and Fluad ® , in particular the rates of injection site pain. The secondary objective was to demonstrate the equivalence (non-inferiority) in immunogenicity for both vaccines. The trial was carried out in compliance with Good Clinical Practice in a Public Health Department (AUSL RMF-Civitavecchia, Rome, Italy) during the influenza vaccination campaign for the 1998–1999 influenza season. Written informed consent was obtained from all participants before study participation. Each was randomly assigned to receive either Vaxigrip ® or Fluad ® . All subjects enrolled in the study were ≥65 years in age and in good health. Demographic data for the subjects included are described in Table 1. Exclusion criteria included: febrile illness ≥37.5 ◦ C on the day of enrolment, influenza vaccine administration within the past 6 months, any other vaccination within the past 15 days (30 days if live virus vaccine), any analgesic treatment on the inclusion day, treatment with corticosteroids on a regular basis (except for local corticosteroids), any bleeding disorder, known allergy to egg protein or suspected allergy to any of the vaccine components and any condition which, in the opinion of the Table 1 Demographic characteristics
Reactogenicity population (N) Mean age (years ± S.D.) Men (%) Immunogenicity population (N) Mean age (years ± S.D.) Men (%)
Vaxigrip ®
Fluad ®
1076 73.3 ± 5.9 49.6
1074 73.4 ± 5.9 52.3
591 73.4 ± 5.6 52.3
595 73.8 ± 5.9 55.8
2.3. Antibody studies Anti-haemagglutinin antibody titres to the three influenza virus haemagglutinins were determined using the haemagglutination inhibition test (HI test) [30,31]. The principle of the HI test is based on the ability of specific anti-influenza antibodies to inhibit haemagglutination of chicken red blood cells (RBC) by influenza virus haemagglutinin (HA). The sera to be tested were previously treated to eliminate the non-specific inhibitors and the anti-species haemagglutinin. Titre is expressed as the reciprocal of the highest dilution of serum that completely inhibited hæmagglutination. A level of 10 or below was regarded as undetectable. For evaluation purposes, a titre value <10 was considered as equal to 5. A titre of 40 was considered as protective. Anti-HI titres to B/Beijing/184/93 were measured using B/Harbin/7/94. The immunogenicity of the two study vaccines was assessed according to the frequency of seroconversion on day 21, the proportion of subjects seroprotected on days 0 and 21 and the increase in geometric mean titre of anti-HI between days 0 and 21, defined as the geometric mean titre ratio (GMTR). Seroconversion was defined as a change from a pre-vaccination titre <10 to a post-vaccination titre ≥40 or a four-fold or greater rise in
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Table 2 Local and systemic reactions Vaxigrip ® (N = 1076)
Any reaction (local or systemic)
Fluad ® (N = 1074)
P value
No. of subjects
Percentage
No. of subjects
Percentage
143
13.3
168
15.6
Any immediate reaction (within 30 min) Any immediate local reaction Any immediate systemic reaction
8 8 –
0.7 0.7 0.0
13 7 6
1.2 0.7 0.6
– 1.000 0.015
Any delayed reaction (30 min to 3 days) Any local reaction Pain at the injection site Any systemic reaction
141 93 42 65
13.1 8.6 3.9 6.0
160 114 71 70
14.9 10.6 6.6 6.5
– 0.125 0.005 0.658
titre in those with an initial anti-HI titre ≥10 [32]. Seroprotection was defined as a titre≥40.
–
the two groups (5% for Vaxigrip ® and 3.8% for Fluad ® ). Only one subject in the Vaxigrip ® group received high doses of corticosteroids.
2.4. Sample size and statistical analysis 3.1. Reactogenicity Reactogenicity: the percentages of local and systemic reactions in the Vaxigrip ® and Fluad ® groups were compared using Fisher’s exact test. The study was based on the hypothesis that Vaxigrip ® and Fluad ® would produce pain at the injection site in the same percentage of subjects. Assuming that the percentages were 12% in the Vaxigrip ® group, and 17% in the Fluad ® group, 1037 subjects per group would have to be analysed to show a significant difference with an α of 5% and a power of 90% in a two-sided test Table 2. Immunogenicity: seroprotection and seroconversion rates for both vaccines were compared using the equivalence (non-inferiority) testing approach, with a one-sided α of 2.5% and a clinically acceptable difference of 10%. All enrolled subjects were included in the reactogenicity analysis. Subjects excluded from the immunogenicity analysis were those non-compliant with the immunisation, blood sampling schedule or those who received medication that could interfere with the immune response.
The overall rates of immediate local reactions (occurring 0–30 min after vaccine administration) were similar for the two groups. Pain at the injection site was observed in 0.1% of Vaxigrip ® subjects (mild) and 0.3% of Fluad ® subjects (mild or moderate). None of the six immediate systemic reactions in the Fluad ® group were serious. The frequency of local and systemic reactions occurring from 30 min to 3 days after vaccination was also low in both groups. There was a statistically significantly lower rate of injection site pain in the Vaxigrip ® group (3.9%) compared with the Fluad ® group (6.6%) (P = 0.005). Other local reactions consisted mainly of erythema and induration. Systemic reactions were less frequent in the Vaxigrip ® group compared with the Fluad ® group (any systemic reaction: 6.0 and 6.5%, respectively). The intensity of most systemic reactions was also mild for both vaccines. Fever ≥37.5 ◦ C was reported in fewer than 1% of vaccinees. None of the nine serious adverse events (SAEs) were considered to be related to either of the study vaccines.
3. Results
3.2. Immunogenicity
A total of 2150 subjects were vaccinated, of these 1076 received Vaxigrip ® and 1074 Fluad ® . The two vaccine groups were similar with respect to demographic characteristics (Table 1). A total of 1186 paired blood specimens (days 0 and 21) were obtained for antibody assessment. Among the 1186 included in the immunogenicity analysis, 591 received Vaxigrip ® and 595 Fluad ® . Of the total study population, 81 subjects (3.8%) withdrew prematurely: 40 (1.86%) in the Vaxigrip ® group and 41 (1.90%) in the Fluad ® group. The majority of premature withdrawals were due to “lost to follow-up”. The number of subjects taking concomitant medications (analgesics, antipyretics and/or corticosteroids) was low and similar among
Paired blood specimens (days 0 and 21) were obtained from 1186 subjects; 591 in the Vaxigrip ® group and 595 in the Fluad ® group. Both vaccines induced increases in anti-HI antibody titres ≥40 (seroprotective titre) in a large proportion of subjects (Table 3; Figs. 1–3). In both groups, more subjects achieved seroprotective titres (≥40) against the A/Sydney/5/97 (H3N2) and A/Beijing/262/95 (H1N1) strains than against the B/Beijing/184/93 strain. Vaxigrip ® was shown to be equivalent (non-inferiority) to Fluad ® regarding seroprotection and seroconversion rates against the A/Sydney/5/97 (H3N2) strain (Table 3, Fig. 1). Furthermore, the geometric mean of titre ratios (GMTR; Table 3) confirmed that the two vaccines were similarly
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Table 3 Geometric mean titres for anti-HI antibodies and seroprotection and seroconversion rates in subjects <75 and ≥75 years in age and in the whole population Vaxigrip ® (N = 591)
Fluad ® (N = 595)
A/Sydney/5/97 (H3N2)
A/Beijing/262/95 (H1N1)
B/Beijing/184/93a
A/Sydney/5/97 (H3N2)
A/Beijing/262/95 (H1N1)
B/Beijing/184/93a
36.8 183.2 5.0
10.4 87.1 8.4
9.2 18.9 2.1
39.9 214.3 5.4
11.3 154.4 13.7
9.3 24.0 2.6
<75 years ≥75 years Whole population
92.4 87.1 90.4
74.9 66.1 71.6
30.9 27.4 29.5
93.8 94.2 94.0
86.4 78.9 83.4
37.7 38.4 38.0
Seroconversiond (%) <75 years ≥75 years Whole population
61.9 58.0 60.4
66.9 59.5 63.7
15.6 12.6 14.5
59.8 62.4 60.8
77.9 73.1 76.0
25.2 17.8 22.2
Pre-GMT ( day 0) Post-GMT (day 21) GMTRb Seroprotectionc (%)
a
Anti-HI antibodies to B/Beijing/184/93 were assessed using B/Harbin/7/94. Geometric mean of anti-HI titre ratio (post/pre). c Anti-HI titre ≥40 on day 21. d Greater than or equal to four-fold rise in anti-HI titre between days 0 and 21. b
Fig. 1. Reverse cumulative distribution curves (RCDs) of the anti-HI titres for the A/Sydney/5/97 (H3N2) strain. The titres are expressed as log10 titres, not as two-fold dilutions (10, 20, 40, etc.).
immunogenic against the A/Sydney/5/97 (H3N2) strain. However, Fluad ® elicited greater increases in GMTRs against the other two strains (A/Beijing/262/95 (H1N1) and B/Beijing/184/93). Seroprotection and seroconversion rates for the two vaccines were also separately assessed in subjects <75 or ≥75 years of age (Table 3). The seroprotection and seroconversion responses to Fluad ® and Vaxigrip ® were similar for the A/Sydney/5/97 (H3N2) strain, in the <75 years of age group. Regarding the other two virus strains, responses were higher in the Fluad ® group. In subjects 75 years of age or
older, Fluad ® was more immunogenic than Vaxigrip ® for all three virus strains.
4. Discussion The safety and effectiveness of inactivated influenza vaccination for elderly people has been demonstrated in several clinical studies [1–9]. Studies carried out among elderly persons in the US and Canada have demonstrated that vaccination prevents approximately 30–50% of deaths
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Fig. 2. Reverse cumulative distribution curves (RCDs) of the anti-HI titres for the A/Beijing/262/95 (H1N1) strain. The titres are expressed as log10 titres, not as two-fold dilutions (10, 20, 40, etc.).
and hospitalisations for influenza-associated respiratory complications [6]. During influenza epidemics, vaccination yields substantial savings in health care costs [7]. The relationship between of anti-HI antibody responses and the clinical efficacy of influenza vaccines is still disputed [24–29]. However, as a surrogate marker for protection, an increase in anti-HI antibody titre has been regularly considered an acceptable measure for evaluating influenza vaccines. For regulatory purposes, anti-HI titres are the basis for the yearly approval of new influenza vaccines. Safety considerations are also important, and can affect acceptance
of influenza vaccines by decision makers responsible for public health programs. In this study, both Vaxigrip ® and Fluad ® were well tolerated. Few local and systemic adverse reactions were observed within 3 days of vaccine administration, although local reactions were slightly more frequent in the Fluad ® group. Vaxigrip ® caused pain at the injection site in a significantly lower proportion of subjects (3.9% for Vaxigrip ® versus 6.6% for Fluad ® ). For both vaccines the intensity of pain was considered mild in most subjects and did not interfere with usual activity.
Fig. 3. Reverse cumulative distribution curves (RCDs) of the anti-HI titres for the B/Beijing/184/93 strain. The titres are expressed as log10 titres, not as two-fold dilutions (10, 20, 40, etc.).
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Systemic adverse reactions after influenza vaccination occurred in low frequencies, as previously observed [21,22]. Fever was reported in a very small percentage of subjects in both groups. Few subjects took antipyretics, analgesics or anti-inflammatory medications following vaccination, another marker of good tolerability. Both vaccines induced good immune responses. Three weeks after vaccination, seroprotection rates were above 60% and seroconversion rates above 30% for the two influenza A strains. Increases in GMT between days 0 and 21 were above 2 for all strains for both vaccines. Significantly, Vaxigrip ® was equivalent to Fluad ® with respect to seroprotection and seroconversion rates against the more virulent A/Sydney/5/97 (H3N2) strain. For subjects ≥75 years in age, Fluad ® was more immunogenic against all three virus strains. Both vaccines produced an increase in the number of subjects protected (titre ≥40) against the A/Sydney/5/97 (H3N2) and A/Beijing/262/95 (H1N1) strains, whereas a lower percentage of subjects achieved a seroprotective titre against the B/Beijing/184/93 strain. A lower antibody response against the influenza B strain was also observed in other studies conducted during the same season [29]. Our findings concerning the reactogenicity and the immunogenicity of Vaxigrip ® and Fluad ® agree with those of other clinical trials [10,15,16]. The feasibility of improving the immunogenicity of conventional influenza vaccines by means of adjuvants (particularly MF59) has been confirmed. This finding is significant with regards to elderly subjects and subjects with chronic diseases. Many of them develop lower antibody responses to conventional inactivated influenza vaccines, in comparison to younger adults. However, the increased immunogenicity of adjuvanted vaccines is associated with a slightly higher frequency of local reactions compared to the conventional vaccine. Thus, it may be preferable to administer adjuvanted influenza vaccines in elderly people and use conventional vaccines in younger subjects.
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