Safety and reactogenicity profile of an adjuvanted H5N1 pandemic candidate vaccine in adults within a phase III safety trial

Advances in Infectious Disease Vaccine Adjuvants

Vaccines are one of the most significant medical interventions in the fight against infectious diseases. Since their discovery by Edward Jenner in 1796, vaccines have reduced the worldwide transmission to eradication levels of infectious diseases, including smallpox, diphtheria, hepatitis, malaria, and influenza. However, the complexity of developing safe and effective vaccines remains a barrier for combating many more infectious diseases. Immune stimulants (or adjuvants) are an indispensable factor in vaccine development, especially for inactivated and subunit-based vaccines due to their decreased immunogenicity compared to whole pathogen vaccines. Adjuvants are widely diverse in structure; however, their overall function in vaccine constructs is the same: to enhance and/or prolong an immunological response. The potential for adverse effects as a result of adjuvant use, though, must be acknowledged and carefully managed. Understanding the specific mechanisms of adjuvant efficacy and safety is a key prerequisite for adjuvant use in vaccination. Therefore, rigorous pre-clinical and clinical research into adjuvant development is essential. Overall, the incorporation of adjuvants allows for greater opportunities in advancing vaccine development and the importance of immune stimulants drives the emergence of novel and more effective adjuvants. This article highlights recent advances in vaccine adjuvant development and provides detailed data from pre-clinical and clinical studies specific to infectious diseases. Future perspectives into vaccine adjuvant development are also highlighted.

A systematic review and meta-analysis on the safety of newly adjuvanted vaccines among older adults

INTRODUCTION

New adjuvants have been developed to improve the efficacy of vaccines and for dose-sparing capacity and may overcome immuno senescence in the elderly. We reviewed the safety of newly-adjuvanted vaccines in older adults.

METHODS

We searched Medline for clinical trials (CTs) including new adjuvant systems (AS01, AS02, AS03, or MF59), used in older adults, published between 01/1995 and 09/2017. Safety outcomes were: serious adverse events (SAEs); solicited local and general AEs (reactogenicity); unsolicited AEs; and potentially immune-mediated diseases (pIMDs). Standard random effects meta-analyses were conducted by type of safety event and adjuvant type, reporting Relative Risks (RR) with 95% confidence intervals (95% CI).

RESULTS

We identified 1040 publications, from which we selected 7, 7, and 12 CTs on AS01/AS02, AS03 and MF59, respectively. 47,602 study participants received newly-adjuvanted vaccine and 44,521 control vaccine, or placebo. Rates of SAEs (RR = 0.99, 95% CI = 0.96-1.02), deaths (RR = 0.99, 95% CI = 0.92-1.06) and pIMDs (RR = 0.94, 95% CI = 0.79-1.1) were comparable in newly-adjuvanted and control groups. Vaccine-related SAEs occurred in <1% of the subjects in both groups. The reactogenicity of AS01/AS02 and AS03 adjuvanted vaccines was higher compared to control vaccines, whereas MF59-adjuvanted vaccines resulted only in more pain. Grade 3 reactogenicity was reported infrequently, with fatigue (RR = 2.48, 95% CI = 1.69-3.64), headache (RR = 2.94, 95% CI = 1.24-6.95), and myalgia (RR = 2.68, 95% CI = 1.86-3.80) occurring more frequently in newly-adjuvanted groups. Unsolicited AEs occurred slightly more frequently in newly-adjuvanted groups (RR = 1.04, 95% CI = 1.00-1.08).

CONCLUSIONS

Our review suggests that, within the clinical trial setting, the use of new adjuvants in older adults has not led to any safety concerns, with no increase in SAEs or fatalities. Higher rates for solicited AEs were observed, especially for AS01/AS02 and AS03 adjuvanted vaccines, but AEs were mostly mild and transient. Further evidence will need to come from the use of new adjuvants in the real-world setting, where larger numbers can be studied to potentially detect rare reactions.

Reactogenicity and safety of AS03B-adjuvanted H5N1 influenza vaccine in children: an open-label, one-way, crossover trial

Background

Human cases of highly pathogenic avian-origin influenza A/H5N1 infection continue to be reported to the World Health Organization, and recent outbreaks of human cases of other zoonotic influenza strains highlight the continued need for strategies to mitigate influenza pandemic potential.

Methods

A Phase II–III randomized, placebo-controlled, observer-blind trial was conducted to assess the immunogenicity, reactogenicity, and safety of two 1.9 μg hemagglutinin doses of AS03B-adjuvanted H5N1 (AS03B-H5N1; A/Indonesia) vaccine in children (6 months to <18 years old) of Thailand, the United States, and Canada (Year 1, published elsewhere). After database lock in Year 1, the trial was unblinded, and children who had been randomized to receive placebo and continued to fulfill the eligibility criteria were invited to participate in an open-label, one-way, crossover safety extension phase, in which they received AS03B-H5N1 vaccine. Here we report the safety analysis in Year 2.

Results

A total of 155 children were vaccinated in Year 2. The most frequent solicited adverse event (AE) during 7 days post vaccination was injection site pain. Irritability or fussiness was reported in about one-third of younger children (aged <6 years) during 7 days post vaccination and was the most common solicited general AE in this age group. Postvaccination temperature (≥38°C) was reported in 4 (5.1%) children. The most common solicited general AEs in older children (aged ≥6 years) were muscle aches, headache, and fatigue. The AS03B-H5N1 vaccine had a clinically acceptable safety profile up to 385 days post vaccination.

Conclusions

Safety in the crossover phase was acceptable and consistent with that observed in vaccine recipients in the randomized, blinded phase of the study.

Clinical trial registration

ClinicalTrials.gov: NCT01310413.

Adjuvanted influenza vaccines

In spite of current influenza vaccines being immunogenic, evolution of the influenza virus can reduce efficacy and so influenza remains a major threat to public health. One approach to improve influenza vaccines is to include adjuvants; substances that boost the immune response. Adjuvants are particularly beneficial for influenza vaccines administered during a pandemic when a rapid response is required or for use in patients with impaired immune responses, such as infants and the elderly. This review outlines the current use of adjuvants in human influenza vaccines, including what they are, why they are used and what is known of their mechanism of action. To date, six adjuvants have been used in licensed human vaccines: Alum, MF59, AS03, AF03, virosomes and heat labile enterotoxin (LT). In general these adjuvants are safe and well tolerated, but there have been some rare adverse events when adjuvanted vaccines are used at a population level that may discourage the inclusion of adjuvants in influenza vaccines, for example the association of LT with Bell's Palsy. Improved understanding about the mechanisms of the immune response to vaccination and infection has led to advances in adjuvant technology and we describe the experimental adjuvants that have been tested in clinical trials for influenza but have not yet progressed to licensure. Adjuvants alone are not sufficient to improve influenza vaccine efficacy because they do not address the underlying problem of mismatches between circulating virus and the vaccine. However, they may contribute to improved efficacy of next-generation influenza vaccines and will most likely play a role in the development of effective universal influenza vaccines, though what that role will be remains to be seen.

AS03- and MF59-Adjuvanted Influenza Vaccines in Children

Influenza is a major cause of respiratory disease leading to hospitalization in young children. However, seasonal trivalent influenza vaccines (TIVs) have been shown to be ineffective and poorly immunogenic in this population. The development of live-attenuated influenza vaccines and adjuvanted vaccines are important advances in the prevention of influenza in young children. The oil-in-water emulsions MF59 and adjuvant systems 03 (AS03) have been used as adjuvants in both seasonal adjuvanted trivalent influenza vaccines (ATIVs) and pandemic monovalent influenza vaccines. Compared with non-adjuvanted vaccine responses, these vaccines induce a more robust and persistent antibody response for both homologous and heterologous influenza strains in infants and young children. Evidence of a significant improvement in vaccine efficacy with these adjuvanted vaccines resulted in the use of the monovalent (A/H1N1) AS03-adjuvanted vaccine in children in the 2009 influenza pandemic and the licensure of the seasonal MF59 ATIV for children aged 6 months to 2 years in Canada. The mechanism of action of MF59 and AS03 remains unclear. Adjuvants such as MF59 induce proinflammatory cytokines and chemokines, including CXCL10, but independently of type-1 interferon. This proinflammatory response is associated with improved recruitment, activation and maturation of antigen presenting cells at the injection site. In young children MF59 ATIV produced more homogenous and robust transcriptional responses, more similar to adult-like patterns, than did TIV. Early gene signatures characteristic of the innate immune response, which correlated with antibody titers were also identified. Differences were detected when comparing child and adult responses including opposite trends in gene set enrichment at day 3 postvaccination and, unlike adult data, a lack of correlation between magnitude of plasmablast response at day 7 and antibody titers at day 28 in children. These insights show the utility of novel approaches in understanding new adjuvants and their importance for developing improved influenza vaccines for children.

Immunogenicity of AS03-adjuvanted and non-adjuvanted trivalent inactivated influenza vaccines in elderly adults: A Phase 3, randomized trial and post-hoc correlate of protection analysis

In this study we describe the immunogenicity results from a subset of older people (N = 5187) who participated in a Phase 3 randomized, observer-blinded trial of AS03-TIV versus TIV (Fluarix™) (ClinicalTrials.gov, NCT00753272). Participants received one dose of AS03-TIV or TIV in each study year and antibody titers against the vaccine strains were assessed using hemagglutination-inhibition (HI) assay at 21 d and 180 d post-vaccination in each vaccine group in the 2008/09 (Year 1) and 2009/10 (Year 2) influenza seasons. Manufacturing consistency of 3 lots of AS03-TIV for HI antibody responses in Year 1 was a co-primary objective. In a post-hoc analysis, a statistical regression model included 4830 subjects in whom immunogenicity and laboratory-confirmed attack rate data were available; the analysis was performed to assess HI antibody titers against A/H3N2 as a correlate of protection for laboratory-confirmed A/H3N2 influenza. AS03-TIV and TIV elicited strong HI antibody responses against each vaccine strain 21 d post-vaccination in both years. The manufacturing consistency of 3 lots of AS03-TIV was demonstrated. In both years and each vaccine group, HI antibody responses were lower for A/H1N1 than the other vaccine strains. Day 180 seroconversion rates (proportion with ≥4-fold increase in titer compared with pre-vaccination titer) in Year 1 in the AS03-TIV and TIV groups, respectively, were 87.7% and 74.1% for A/H3N2, 69.7% and 59.6% for influenza B, and 58.3% and 47.4% for A/H1N1. The post-hoc statistical model based on A/H3N2 attack rates and HI antibody titers estimated that a 4-fold increase in post-vaccination titers against A/H3N2 was associated with a 2-fold decrease in the odds of A/H3N2 infection.

A phase 1, open-label safety and immunogenicity study of an AS03-adjuvanted trivalent inactivated influenza vaccine in children aged 6 to 35 months

Background: There is a need for better vaccines and vaccine strategies to reduce the burden of influenza in very young children.

 

Methods: This phase 1, open-label study assessed the reactogenicity, safety, and immunogenicity of an inactivated trivalent influenza vaccine (TIV) containing low doses of hemagglutinin antigen (7.5 µg each strain), adjuvanted with a tocopherol-based oil-in-water emulsion Adjuvant System (AS03). Influenza vaccine-naïve children aged 6–35 months were sequentially enrolled to receive TIV-AS03_D (1.48 mg tocopherol) or TIV-AS03_C (2.97 mg tocopherol), then a 6-month booster of conventional TIV. The primary endpoint was the incidence of fever (axillary temperature >38 °C) for 7 days post-vaccination. Immune responses were assessed by hemagglutination-inhibition (HI) assay.

Results: Forty children were sequentially enrolled into the TIV-AS03_D or the TIV-AS03_C group. Fever >38.0 °C was reported in 5/20 (25.0%) and 7/20 (35.0%) children after the first and second doses of TIV-AS03_D, respectively, and in 7/20 (35.0%) children after 1 dose of TIV-AS03_C; the latter fulfilled the holding rule for safety, and the second dose of TIV-AS03_C was cancelled. HI immune responses exceeded adult European licensure criteria for the immunogenicity, and all children had HI antibody titers ≥ 1:40 after 1 dose of TIV booster against booster strains.

Conclusions: One dose of primary vaccine containing a low dose of antigen and AS03 may be a possible influenza vaccination strategy for young children. The relatively high frequency of fever warrants further investigation, although the generalizability of the findings are uncertain given that many of the children had antibody evidence suggesting recent infection with A(H1N1)pdm09.

Immunogenicity and safety of an AS03-adjuvanted H5N1 pandemic influenza vaccine in Korean adults: a phase IV, randomized, open-label, controlled study

BACKGROUND

AS03-adjuvanted H5N1 pandemic influenza vaccines have been assessed in an extensive clinical development program conducted in North America, Europe, and Asia including children from 6 months of age, adults, and elderly adults. We evaluated AS03-H5N1 in Korean adults 18 through 60 years of age.

METHODS

This Phase IV, randomized, study was conducted to assess the immunogenicity, reactogenicity, and safety of two doses (3.75μg of hemagglutinin antigen) of A/Indonesia/5/2005 (H5N1) adjuvanted with AS03 given 21 days apart in Korean adults. Antibody responses were assessed using hemagglutination-inhibition (HI) assays against the vaccine strain and a vaccine-heterologous strain (A/Vietnam/1194/2004) 21 days after the second dose. A control group (safety) received a licensed seasonal inactivated trivalent influenza vaccine (TIV). Reactogenicity was assessed for 7 days after each vaccination, and unsolicited adverse events were assessed for 182 days following vaccination in both study groups (NCT01730378).

RESULTS

AS03-H5N1 was immunogenic and elicited robust HI antibody responses with seroconversion rates of 100% for the vaccine strain and 69.1% for the heterologous strain (N=81). HI antibody responses fulfilled the European licensure criteria for immunogenicity (primary endpoint). The incidence of local and systemic solicited adverse events (reactogenicity) was higher with AS03-H5N1 than TIV. There was no apparent difference in the rate of unsolicited adverse events in the AS03-H5N1 and TIV groups.

CONCLUSION

The results indicate that AS03-H5N1 vaccine is immunogenic with reactogenicity and safety findings that are consistent with the established profile of AS03-H5N1 vaccine.

Safety of AS03-adjuvanted inactivated split virion A(H1N1)pdm09 and H5N1 influenza virus vaccines administered to adults: pooled analysis of 28 clinical trials

Clinical trials have shown that AS03-adjuvanted H5N1 and A(H1N1)pdm09 vaccines are highly immunogenic, although with an increased reactogenicity profile relative to non-adjuvanted vaccines in terms of the incidence of common injection site and systemic adverse events (AEs). We evaluated pooled safety data from 22,521 adults who had received an AS03-adjuvanted H5N1 or A(H1N1)pdm09 influenza or control vaccine with the purpose to identify medically-attended AEs (MAEs), including subsets of serious AEs (SAEs), potentially immune-mediated diseases (pIMDs), and AEs of special interest (AESI), and to explore a potential association of these AEs with the administration of an AS03-adjuvanted influenza vaccine. For participants who had received an AS03-adjuvanted vaccine, the relative risks (RRs) for experiencing a MAE or a SAE compared to control group (participants who had received a non-adjuvanted vaccine or saline placebo) were 1.0 (95% confidence interval [CI]: 0.9; 1.1) and 1.1 (95% CI: 0.9; 1.4), respectively. The overall RRs for experiencing an AESI or a pIMD (AS03-adjuvanted vaccine/control) were 1.2 (95% CI: 0.9; 1.6) and 1.7 (95% CI: 0.8; 3.8), respectively. Thirty-8 participants in the AS03-adjuvanted vaccine group had a pIMD reported after vaccine administration, yielding an incidence rate (IR) of 351.9 (95% CI: 249.1; 483.1) per 100,000 person-years. The estimated IRs in the AS03-adjuvanted vaccine group were greater than the literature reported rates for: facial paresis/VIIth nerve paralysis, celiac disease, thrombocytopenia and ulcerative colitis. These results do not support an association between AS03-adjuvanted H5N1 and A(H1N1)pdm09 vaccines and the AEs collected in the trials included in the analysis.

The safety and immunogenicity of a MF59-adjuvanted H5N1 prepandemic influenza vaccine in healthy adults primed with homologous or heterologous H5N1 vaccines: an observational study

Background

World Health Organization (WHO) has recommended individuals with increased risk of contracting influenza A H5N1 infection to be immunized against the virus during the inter-pandemic period. Safety and immunogenicity of H5N1 vaccine among participants primed with homologous or heterologous H5N1 vaccines produced by diverse manufactures have not been reported.

Methods

Healthy individuals aged 20 to 60 years old were recruited and stratified into three groups: participants without priming (control group), participants primed with A/Indonesia/05/2005 vaccine, participants primed with A/Vietnam/1194/2004 vaccine and A/Indonesia/05/2005 vaccine. Enrolled participants received two doses of MF59-adjuvanted A/Vietnam/1194/2004 vaccine (study vaccine). Solicited reactions were recorded by vaccine recipients. Blood samples were obtained for hemagglutination inhibition test.

Results

A total of 131 participants were enrolled. No significant adverse events were recorded. Tenderness, fatigue and general muscle ache were the most common solicited reactions which alleviated within one week of immunization. Three weeks after two doses of the study vaccine, 63%, 68% and 88% were in seroprotective status in the control group, A/Indonesia/05/2005 primed group and A/Vietnam/1194/2004 and A/Indonesia/05/2005 primed group, respectively. Participants primed with A/Vietnam/1194/2004 and A/Indonesia/05/2005 showed high immune response after booster with one dose of the study vaccine.

Conclusion

The study vaccine did not cause severe adverse events. It elicited mostly mild to moderate reactions among participants. Participants primed with A/Vietnam/1194/2004 and A/Indonesia/05/2005 vaccine showed higher immune response than those without priming or primed with A/Indonesia/05/2005 vaccine. The report suggested those with an increased risk of influenza A H5N1 virus exposure may benefit from receiving influenza A H5N1 priming during the inter-pandemic period if the antigenicity of the pandemic influenza strain is similar to that of the priming strain.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0587-z) contains supplementary material, which is available to authorized users.

AS03B-adjuvanted H5N1 influenza vaccine in children 6 months through 17 years of age: a phase 2/3 randomized, placebo-controlled, observer-blinded trial

BACKGROUND

This phase 2/3, randomized, placebo-controlled, observer-blinded study assessed the immunogenicity, reactogenicity, and safety of an inactivated, split-virion H5N1 influenza vaccine (A/Indonesia/5/2005) in children aged 6 months through 17 years.

METHODS

Children received 2 influenza vaccine doses 21 days apart, each containing 1.9 µg of hemagglutinin and AS03B adjuvant (5.93 mg of α-tocopherol). The randomization ratio was 8:3 for vaccine to placebo, with equal allocation between 3 age strata (6-35 months, 3-8 years, and 9-17 years). Immunogenicity against the vaccine strain was assessed 21 days after the first and second vaccine doses for all vaccinees, at day 182 for half, and at day 385 for the remaining half. Reactogenicity after each dose and safety up to 1 year after vaccination were evaluated.

RESULTS

Within each age stratum, the lower limit of the 98.3% confidence interval for the day 42 seroprotection rate was ≥70%, thus fulfilling the US and European licensure criteria. The immune responses elicited by vaccine persisted well above baseline levels for 1 year. The vaccine was more reactogenic than placebo, but no major safety concerns were identified.

CONCLUSIONS

AS03B-adjuvanted H5N1 influenza vaccine was immunogenic and showed an acceptable safety profile in all age groups studied. Clinical Trials Registration: NCT01310413.

Heterologous prime-boost vaccination using an AS03B-adjuvanted influenza A(H5N1) vaccine in infants and children<3 years of age

Background. Protecting young children from pandemic influenza should also reduce transmission to susceptible adults, including pregnant women.

Methods. An open study assessed immunogenicity and reactogenicity of a heterologous booster dose of A/turkey/Turkey/1/2005(H5N1)-AS03_B (AS03_B is an Adjuvant System containing α-tocopherol and squalene in an oil-in-water emulsion [5.93 mg tocopherol]) in infants and children aged 6 to < 36 months that was given 6 months following 2-dose primary vaccination with A/Indonesia/05/2005(H5N1)-AS03_B. Vaccines contained 1.9 µg of hemagglutinin antigen and AS03_B. Hemagglutinin inhibition (HI) responses, microneutralization titers, and antineuraminidase antibody levels were assessed for 6 months following the booster vaccination.

Results. For each age stratum (defined on the basis of the subject's age at first vaccination as 6 to < 12 months, 12 to < 24 months, and 24 to < 36 months) and overall (n = 113), European influenza vaccine licensure criteria were fulfilled for responses to A/turkey/Turkey/1/2005(H5N1) 10 days following the booster vaccination. Local pain and fever increased with consecutive doses. Anamnestic immune responses were demonstrated for HI, neutralizing, and antineuraminidase antibodies against vaccine-homologous/heterologous strains. Antibody responses to vaccine-homologous/heterologous strains persisted in all children 6 months following the booster vaccination.

Conclusions. Prevaccination of young children with a clade 2 strain influenza A(H5N1) AS03-adjuvanted vaccine followed by heterologous booster vaccination boosted immune responses to the homologous strain and a related clade, with persistence for at least 6 months. The results support a prime-boost vaccination approach in young children for pandemic influenza preparedness.

Clinical Trials Registration. NCT01323946.

Pandemic influenza A H1N1 vaccines and narcolepsy: vaccine safety surveillance in action

The 2009 influenza A H1N1 pandemic placed unprecedented demand on public health authorities and the vaccine industry. Efforts were coordinated internationally to maximise the speed of vaccine development, distribution, and delivery, and the European Union's novel fast-track authorisation procedures mandated increased postmarketing surveillance to monitor vaccine safety. Clinicians in Finland and Sweden later identified an apparent increase in the incidence of narcolepsy associated with a specific adjuvanted pandemic influenza vaccine. After extensive review, the European Medicines Agency confirmed the existence of this association, which has since been detected in England, Ireland, France, and Norway. Assessments of the causal mechanisms continue. In this Review, we discuss how the narcolepsy association was detected, and we present the evidence according to the causality assessment criteria for adverse events following immunisation. The lessons learnt emphasise the central role of alert clinicians in reporting of suspected adverse reactions, and the importance of internationally robust postmarketing surveillance strategies as crucial components in future mass immunisation programmes.

H5N1 vaccines in humans

The spread of highly pathogenic avian H5N1 influenza viruses since 1997 and their virulence for poultry and humans has raised concerns about their potential to cause an influenza pandemic. Vaccines offer the most viable means to combat a pandemic threat. However, it will be a challenge to produce, distribute and implement a new vaccine if a pandemic spreads rapidly. Therefore, efforts are being undertaken to develop pandemic vaccines that use less antigen and induce cross-protective and long-lasting responses, that can be administered as soon as a pandemic is declared or possibly even before, in order to prime the population and allow for a rapid and protective antibody response. In the last few years, several vaccine manufacturers have developed candidate pandemic and pre-pandemic vaccines, based on reverse genetics and have improved the immunogenicity by formulating these vaccines with different adjuvants. Some of the important and consistent observations from clinical studies with H5N1 vaccines are as follows: two doses of inactivated vaccine are generally necessary to elicit the level of immunity required to meet licensure criteria, less antigen can be used if an oil-in-water adjuvant is included, in general antibody titers decline rapidly but can be boosted with additional doses of vaccine and if high titers of antibody are elicited, cross-reactivity against other clades is observed. Prime-boost strategies elicit a more robust immune response. In this review, we discuss data from clinical trials with a variety of H5N1 influenza vaccines. We also describe studies conducted in animal models to explore the possibility of reassortment between pandemic live attenuated vaccine candidates and seasonal influenza viruses, since this is an important consideration for the use of live vaccines in a pandemic setting.

Safety of AS03-adjuvanted split-virion H1N1 (2009) pandemic influenza vaccine: a prospective cohort study

OBJECTIVES

To assess the safety of an AS03-adjuvanted split virion H1N1 (2009) vaccine (Pandemrix) in persons vaccinated during the national pandemic influenza vaccination campaign in the UK.

DESIGN

Prospective, cohort, observational, postauthorisation safety study.

SETTING

87 general practices forming part of the Medical Research Council General Practice Research Framework and widely distributed throughout England.

PARTICIPANTS

A cohort of 9143 individuals aged 7 months to 97 years who received at least one dose of the AS03-adjuvanted H1N1 pandemic vaccine during the national pandemic influenza vaccination campaign in the UK was enrolled. 94% completed the 6-month follow-up. Exclusion criteria were previous vaccination with other H1N1 pandemic vaccine and any child in care.

PRIMARY AND SECONDARY OUTCOME MEASURES

Medically attended adverse events (MAEs) occurring within 31 days after any dose, serious adverse events (SAEs) and adverse events of special interest (AESIs) following vaccination were collected for all participants. Solicited adverse events (AEs) were assessed in a subset of participants.

RESULTS

MAEs were reported in 1219 participants and SAEs in 113 participants during the 31-day postvaccination period. The most frequently reported MAEs and SAEs were consistent with events expected to be reported during the winter season in this population: lower respiratory tract infections, asthma and pneumonia. The most commonly reported solicited AEs were irritability in young children aged <5 years (61.8%), muscle aches in children aged 5-17 years (61.9%) and adults (46.9%). 18 AESIs, experienced by 14 patients, met the criteria to be considered for the observed-to-expected analyses. AESIs above the expected number were neuritis (1 case within 31 days) and convulsions (8 cases within 181 days). There were 41 deaths during the 181-day period after vaccination, fewer than expected.

CONCLUSIONS

Results indicate that the AS03-adjuvanted H1N1 pandemic vaccine showed a clinically acceptable reactogenicity and safety profile in all age and risk groups studied.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT00996853.

Safety of seasonal influenza and influenza A (H1N1) 2009 monovalent vaccines in pregnancy

Inactivated influenza vaccines have been given to pregnant women since 1964. Since 2004, the Advisory Committee on Immunization Practices has recommended that pregnant women receive trivalent inactivated influenza vaccine at any time during pregnancy. Studies conducted before 2009 did not identify any safety concerns after trivalent inactivated influenza vaccine in mothers or their infants. During the 2009-2010 influenza A (H1N1) influenza vaccination program, several monitoring systems were established or enhanced to assess whether adverse events were associated with H1N1 2009 monovalent vaccines (2009 H1N1 influenza vaccines). Data from these systems did not identify any safety concerns in pregnant women who received 2009 H1N1 influenza vaccines or their infants. Although live attenuated influenza vaccines are not recommended in pregnant women, a small number of studies have not shown any safety concern among pregnant women or their infants who were inadvertently exposed to these vaccines. This review summarizes US and international safety data for influenza vaccines in pregnant women with an emphasis on 2009 H1N1 influenza vaccines.

Cross-protection against drifted influenza viruses: options offered by adjuvanted and intradermal vaccines

Antigenic drift, the evolutionary mechanism of influenza viruses, results in an increased susceptibility of vaccinated subjects against circulating viruses. New vaccines able to grant a broader and cross-reactive immune response against drifted influenza variants are needed. Several strategies were explored to enhance the immunogenicity of plain vaccines: adjuvants, carriers and intradermal administration of influenza vaccine emerge as a promising options. To evaluate the ability of a MF59-adjuvanted and intradermal influenza vaccine to elicit an effective antibody response against circulating viruses presenting antigenic patterns different from those of the vaccine strains, we compared antibody responses elicited by "implemented" vaccines and conventional intramuscular trivalent inactivated vaccine against heterologous circulating influenza A viruses. Different studies, simulating different epidemiological pictures produced by the natural antigenic drift of seasonal influenza viruses, highlighted the superior cross-reactivity of the antibodies elicited by MF59 and intradermal vaccines, compared with subunit or split vaccine against heterologous viruses.

Safety of AS03-adjuvanted split-virion H1N1 (2009) pandemic influenza vaccine: a prospective cohort study

OBJECTIVES

To assess the safety of an AS03-adjuvanted split virion H1N1 (2009) vaccine (Pandemrix) in persons vaccinated during the national pandemic influenza vaccination campaign in the UK.

DESIGN

Prospective, cohort, observational, postauthorisation safety study.

SETTING

87 general practices forming part of the Medical Research Council General Practice Research Framework and widely distributed throughout England.

PARTICIPANTS

A cohort of 9143 individuals aged 7 months to 97 years who received at least one dose of the AS03-adjuvanted H1N1 pandemic vaccine during the national pandemic influenza vaccination campaign in the UK was enrolled. 94% completed the 6-month follow-up. Exclusion criteria were previous vaccination with other H1N1 pandemic vaccine and any child in care.

PRIMARY AND SECONDARY OUTCOME MEASURES

Medically attended adverse events (MAEs) occurring within 31 days after any dose, serious adverse events (SAEs) and adverse events of special interest (AESIs) following vaccination were collected for all participants. Solicited adverse events (AEs) were assessed in a subset of participants.

RESULTS

MAEs were reported in 1219 participants and SAEs in 113 participants during the 31-day postvaccination period. The most frequently reported MAEs and SAEs were consistent with events expected to be reported during the winter season in this population: lower respiratory tract infections, asthma and pneumonia. The most commonly reported solicited AEs were irritability in young children aged <5 years (61.8%), muscle aches in children aged 5-17 years (61.9%) and adults (46.9%). 18 AESIs, experienced by 14 patients, met the criteria to be considered for the observed-to-expected analyses. AESIs above the expected number were neuritis (1 case within 31 days) and convulsions (8 cases within 181 days). There were 41 deaths during the 181-day period after vaccination, fewer than expected.

CONCLUSIONS

Results indicate that the AS03-adjuvanted H1N1 pandemic vaccine showed a clinically acceptable reactogenicity and safety profile in all age and risk groups studied.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT00996853.

An assessment of prime-boost vaccination schedules with AS03A -adjuvanted prepandemic H5N1 vaccines: a randomized study in European adults

BACKGROUND

Long-term persistence of immune response and safety of an H5N1 prepandemic influenza vaccine adjuvanted with AS03 (an α-tocopherol oil-in-water emulsion-based adjuvant system) was evaluated using various prime-boost schedules that mimicked potential pandemic scenarios (NCT00430521).

METHODS

Five hundred and twelve healthy adults aged 18-60 years received primary vaccination with one or two doses (0, 21 days schedule) of the A/Vietnam/1194/2004 H5N1 vaccine followed by a booster dose (A/Vietnam/1194/2004 or A/Indonesia/05/2005 strain) six or twelve months later across eight randomized groups. Immunogenicity results by hemagglutination inhibition [HI] assay, microneutralization assay, and the cell-mediated immune response (CMI) are reported here for the four groups boosted at Month 12.

RESULTS

A one-dose-adjuvanted primary administration followed 12 months later by a single-adjuvanted booster dose containing a heterologous vaccine strain met or exceeded all US and European criteria for both strains. Increasing the interval between the first and second dose (from 21 days to 12 months) resulted in stronger cross-reactive immune responses against the A/Indonesia/05/2005 strain. The HI antibody response against the two strains persisted for 6 months after the booster dose irrespective of the booster vaccine's strain. The neutralizing antibody responses and the CMI observed in the study population paralleled the HI immune response. Overall, the vaccine had a clinically acceptable safety profile.

CONCLUSION

The H5N1 vaccine in this study allowed for flexibility in the time interval between primary and booster vaccination and the use of a heterologous strain without impacting the strength of the humoral and cellular immune response to both vaccine strains.

Flexibility of interval between vaccinations with AS03A-adjuvanted influenza A (H1N1) 2009 vaccine in adults aged 18-60 and >60 years: a randomized trial

BACKGROUND

Flexibility of vaccination schedule and lower antigen content can facilitate pandemic vaccine coverage. We assessed the immune response and safety of AS03-adjuvanted A/California/7/2009 H1N1 pandemic vaccine containing half of the registered adult haemagglutinin (HA) antigen content, administered as a two-dose schedule at intervals of 21 days or 6 months in both young and elderly adults.

METHODS

In this open-label randomized trial, healthy adults aged 18-60 years (N = 163) and >60 years (N = 143) received AS03A-adjuvanted A/California/7/2009 H1N1 vaccine containing 1.9 μg HA on Day 0. A second dose was given on Day 21 (n = 177) or Day 182 (n = 106). Haemagglutination-inhibition (HI) antibody responses were analyzed on Days 0, 21, 42, 182, 364 and additionally on Day 203 for subjects vaccinated on Day 182. Solicited and unsolicited adverse events were recorded.

RESULTS

The HI antibody response in both age strata 21 days after the first dose met and exceeded all regulatory acceptance criteria although the results suggested a lower response in the older age stratum (geometric mean titres [GMTs] for HI antibodies of 420.5 for subjects aged 18-60 years and 174.4 for those >60 years). A second dose of AS03A adjuvanted A/H1N1/2009 vaccine induced a further increase in antibody titres and the response was similar whether the second dose was administered at 21 days (GMTs of 771.8 for 18-60 years and 400.9 for >60 years) or 6 months (GMTs of 708.3 for 18-60 years and 512.1 for >60 years) following the first dose. Seroprotection rates remained high at 6 months after one dose or two doses while at 12 months rates tended to be higher for the 6 month interval schedule (93.3% for 18-60 years and 80.4% for >60 years) than the 21 day schedule (82.3% for 18-60 years and 50.0% for >60 years). Reactogenicity/safety profiles were similar for both schedules, there was no evidence of an increase in reactogenicity following the second dose.

CONCLUSIONS

The results indicate that flexibility in the dosing interval for AS03A adjuvanted vaccine may be possible. Such flexibility could help to reduce the logistic stress on delivery of pandemic vaccination programmes.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT00975884.

Development and evaluation of AS03, an Adjuvant System containing α-tocopherol and squalene in an oil-in-water emulsion

AS03 is an Adjuvant System composed of α-tocopherol, squalene and polysorbate 80 in an oil-in-water emulsion. In various nonclinical and clinical studies, high levels of antigen-specific antibodies were obtained after administration of an AS03-adjuvanted vaccine, permitting antigen-sparing strategies. AS03 has been shown to enhance the vaccine antigen-specific adaptive response by activating the innate immune system locally and by increasing antigen uptake and presentation in draining lymph nodes, a process that is modulated by the presence of α-tocopherol in AS03. In nonclinical models of the AS03-adjuvanted prepandemic H5N1 influenza vaccine, increased levels of anti-influenza antibody afforded protection against disease and against virus replication of influenza strains homologous and heterologous to the vaccine strain. By incorporating AS03 in the pandemic H1N1/2009 vaccine, vaccine immunogenicity was increased compared with nonadjuvanted H1N1 vaccines. High H1N1/2009/AS03 vaccine effectiveness was demonstrated in several assessments in multiple populations. Altogether, the nonclinical and clinical data illustrate the ability of AS03 to induce superior adaptive responses against the vaccine antigen, principally in terms of antibody levels and immune memory. In general, these results support the concept of Adjuvant Systems as a plausible approach to develop new effective vaccines.

Safety and immunogenicity of a split-virion AS03A-adjuvanted A/Indonesia/05/2005 (H5N1) vaccine in Taiwanese adults

BACKGROUND/PURPOSE

This study evaluated the immune response elicited by two formulations of an AS03(A)-adjuvanted H5N1 A/Indonesia/05/2005 prepandemic influenza vaccine, developed using manufacturing processes with or without thiomersal. In addition, it also evaluated compliance to the Centre for Biologics Evaluation and Research and Committee for Medicinal Products for Human Use (CHMP) immunogenicity guidance criteria for pandemic influenza vaccines in adults.

METHODS

This phase III, observer-blind, randomized study (NCT00812981) enrolled 320 subjects aged 18-60 years into two groups to receive, 21 days apart, two doses of the formulation manufactured using either the thiomersal-containing process (Group TC) or the thiomersal-free process (Group TF). Blood samples collected before vaccination, 21 days after the second vaccine dose, and 6 months following the first vaccine dose (Days 0, 42, and 180) were analysed using a hemagglutination inhibition (HI) assay. Safety assessments were made for the entire study period.

RESULTS

Twenty-one days after the second dose of vaccine, both groups met the CHMP criteria for vaccine-homologous HI response (seroprotection rates/seroconversion rates ≥ 98.7%, seroconversion factor ≥ 121.9) and also for a heterologous HI response against the A/Vietnam/1194/2004 strain (seroprotection rates/seroconversion rates ≥ 81.3%, seroconversion factor ≥ 10.8). Six months after the first dose of vaccine, a marked persistence of the vaccine-homologous HI response was observed that still met one or more CHMP criteria. Pain at the injection site (Group TF 95%, Group TC 91.8%) and myalgia (Group TF 68.8%, Group TC 63.5%) were the most frequently recorded solicited symptoms. Overall, both formulations had a clinically acceptable safety profile.

CONCLUSION

Administration of two doses of the AS03(A)-adjuvanted H5N1 prepandemic influenza vaccine was found to be highly immunogenic in adults with a clinically acceptable safety profile. The ability to confer cross-clade protective immunity makes it a suitable option for mitigation of the morbidity and mortality of outbreaks and pandemics due to H5N1 and drifted strains.

Motivations for participating in a clinical trial on an avian influenza vaccine

In this study we describe the sociodemographic characteristics of people participating in a clinical trial on the safety and immunogenicity of a H5N1 influenza vaccine and we identify the main motivations for joining it.

Rapid immunization against H5N1: a randomized trial evaluating homologous and cross-reactive immune responses to AS03(A)-adjuvanted vaccination in adults

Background. Accelerated immunization schedules may help gain early control of influenza pandemics. We investigated different schedules of an AS03_A-adjuvanted H5N1 vaccine.

Methods. This phase II, open-label, 6-month study randomized participants (aged 18–64 years) to 2 vaccine doses administered 21 (standard schedule), 14, or 7 days apart, or on the same day. Coprimary end points were that the lower limit of the 98.75% confidence interval 14 days after the last dose must be (1) >40% for seroconversion rate (SCR) (Center for Biologics Evaluation and Research [CBER] criterion) and (2) >50% for seroprotection rate (SPR) (attainment rate for reciprocal hemagglutination inhibition titers ≥40, protocol-defined criterion) for the vaccine homologous strain (A/Indonesia/5/2005). European Committee for Human Medicinal Products (CHMP) immunogenicity criteria were also evaluated.

Results. Coprimary end points were achieved (lower 98.75% confidence intervals exceeded defined values). Titers were highest with the standard schedule. Nevertheless, CBER SCR, protocol-defined SPR, and CHMP criteria were met with all schedules for the A/Indonesia/5/2005 strain. There were no significant differences between age groups (18–40 vs 41–64 years). Immune response was robust against drift variants A/turkey/Turkey/1/2005 and A/Vietnam/1194/2004.

Conclusions. The AS03_A-adjuvanted H5N1 vaccine in accelerated schedules offers a robust immune response against vaccine homologous and drift variant strains, allowing consideration of compressed vaccination intervals.

Clinical Trials Registration. NCT00695669.

Evaluation of a virosomal H5N1 vaccine formulated with Matrix M™ adjuvant in a phase I clinical trial

The avian influenza H5 virus epizootic continues to cause zoonosis with human fatalities, highlighting the continued need for pandemic preparedness against this subtype. This study evaluated the tolerability and immunogenicity of a Matrix M™ adjuvanted virosomal H5N1 vaccine in a phase I clinical trial. Sixty healthy adults were vaccinated intramuscularly with two doses of influenza H5N1 (NIBRG-14) virosomal vaccine alone (30 μg haemagglutinin (HA)) or 1.5, 7.5 or 30 μg HA formulated with 50 μg Matrix M™ adjuvant. The antibody response was analysed by haemagglutination inhibition (HI), microneutralisation (MN) and single radial haemolysis (SRH) assays. The vaccine was well tolerated in all groups but injection site pain was more frequently observed in the Matrix M™ adjuvanted groups. The vaccine elicited homologous and heterologous H5N1-specific antibody responses and the Matrix M™ adjuvanted formulations met all the EU regulatory criteria. In conclusion, Matrix M™ adjuvant was well tolerated and augmented the antibody response allowing considerable dose sparing down to 1.5 μg HA.

Dose-sparing H5N1 A/Indonesia/05/2005 pre-pandemic influenza vaccine in adults and elderly adults: a phase III, placebo-controlled, randomized study

BACKGROUND

Highly pathogenic avian influenza H5N1 viruses remain a threat to human health, with potential to become pandemic agents.

METHODS

This phase III, placebo-controlled, observer-blinded study evaluated the immunogenicity, cross-reactivity, safety, and lot consistency of 2 doses of oil-in-water (AS03(A)) adjuvanted H5N1 A/Indonesia/05/2005 (3.75 μg hemagglutinin antigen) prepandemic candidate vaccine in 4561 adults aged 18-91 years.

RESULTS

Humoral antibody responses in the H5N1 vaccine groups fulfilled US and European immunogenicity licensure criteria for pandemic vaccines in all age strata 21 days after the second dose. At 6 months after the administration of the primary dose, serum antibody seroconversion rates continued to fulfill licensure criteria. Neutralizing cross-clade immune responses were demonstrated against clade 1 A/Vietnam/1194/2004. Consistency was demonstrated for 3 consecutive H5N1 vaccine lots. Temporary injection-site pain was more frequent with H5N1 vaccine than placebo (89.3% and 70.7% in the 18-64 and ≥65 years strata vs 22.2% and 14.4% in the placebo groups). Unsolicited adverse event frequency, including medically attended and serious events, was similar between groups through day 364.

CONCLUSIONS

In adults and elderly adults, AS03(A)-adjuvanted H5N1 candidate vaccine was highly immunogenic for A/Indonesia/05/2005, with cross-reactivity against A/Vietnam/1194/2004. Temporary injection site reactions were more frequent with H5N1 vaccine than placebo, although the H5N1 vaccine was well tolerated overall. Clinical Trials Registration. NCT00616928.

Immunogenicity profile of a 3.75-μg hemagglutinin pandemic rH5N1 split virion AS03A-adjuvanted vaccine in elderly persons: a randomized trial

Background. Elderly persons often experience a reduced immune response to influenza vaccination. We evaluated the usual dose of AS03_A-adjuvanted H5N1 pandemic vaccine (3.75 μg hemagglutinin of A/Vietnam/1194/2004-like strain) compared with a double dose in an elderly population.

Methods. This phase 2, open-label study (NCT00397215; http://www.clinicaltrials.gov) randomized participants (age, ≥61 years) to receive, on days 0 and 21: (1) a single dose of AS03_A-adjuvanted vaccine (n = 152), (2) a single dose of nonadjuvanted vaccine (n = 54), (3) a double dose of AS03_A-adjuvanted vaccine (n = 145), or (4) a double dose of nonadjuvanted vaccine (n = 44). The primary end point was hemagglutination inhibition (HI) and neutralizing antibody response against vaccine antigen (according-to-protocol cohort).

Results. Day 42 geometric mean titers for HI antibodies were 126.8 and 237.3 for single and double doses of the AS03_A-adjuvanted vaccine, respectively. Corresponding values for neutralizing antibodies were 447.3 and 595.8. Although the immune response was higher with the double dose, European Committee for Human Medicinal Products criteria for seroconversion and seroprotection rates were achieved in both AS03_A-adjuvanted groups. Antigen-specific CD4 T cell responses were elicited. Immune response persistence at 6 months was high. Immune response in the non-adjuvanted groups was considerably less.

Conclusions. The AS03_A-adjuvanted H5N1 vaccine can be administered elderly persons at the same dose and schedule as in younger adults.

Pregnancy and safety outcomes in women vaccinated with an AS03-adjuvanted split virion H1N1 (2009) pandemic influenza vaccine during pregnancy: a prospective cohort study

Infection with influenza virus during pregnancy poses a significant risk of complications for both mother and fetus. During the H1N1 2009 pandemic, pregnant women constituted one of the priority groups for vaccination in many countries, creating a need for close monitoring of the safety of the vaccine in pregnant women. We present findings from an analysis of a cohort of pregnant women (N=267) from a prospective, observational, post-authorization safety study of the AS03-adjuvanted split virion H1N1 (2009) pandemic vaccine. There were 265 known pregnancy outcomes with 261 live births, four spontaneous abortions with no congenital anomalies, and no stillbirths. There were six live births with congenital anomalies, of which one was diagnosed before vaccination. A total of 247 women (94.6%), of whom four had twin pregnancies, delivered at term, and 14 women (5.4%), of whom two had twin pregnancies, delivered preterm (between Weeks 24 and 36 of gestation), with three of them (1.1%) occurring before 32 weeks (very preterm). Twenty-one neonates (8.1%) had a low birth weight (<2.5 kg), of whom nine (3.5%) were term neonates. The prevalence of all outcomes was in line with the expected rates. The adverse events reported were consistent with the events anticipated to be reported by this study population. No adverse events of special interest were reported. The results of this analysis suggest that exposure to the AS03 adjuvanted H1N1 (2009) vaccine during pregnancy does not increase the risk of adverse pregnancy outcomes including spontaneous abortion, congenital anomalies, preterm delivery, low birth weight neonates, or maternal complications. Although limited in size, the fully prospective nature of the safety follow-up of these women vaccinated during pregnancy is unique and offers an important degree of reassurance for the use of the AS03 adjuvanted H1N1 (2009) vaccine in this high risk group for H1N1 infection.

Evaluation of adjuvanted pandemic H1N1(2009) influenza vaccine after one and two doses in young children

BACKGROUND

When Canada chose an adjuvanted influenza A H1N1(2009) vaccine for pandemic control, dosing requirements and safety in children were unknown. This study compared responses after 1 and 2 doses in young children.

METHODS

Five Canadian centers evaluated ASO3-adjuvanted H1N1(2009) vaccine (Arepanrix, GSK Laval, Quebec) in children aged 6 to 35 months, given 2 doses (0.25 mL, 1.9 μg hemagglutinin) 21 days apart. Blood was collected at baseline and 21 to 28 days after each dose to measure hemagglutination inhibition antibody titers. Adverse events were documented daily for 7 days after each dose.

RESULTS

Centers enrolled 167 children (mean age, 19 months). At baseline, 29 children (17.4%) had hemagglutination inhibition titers ≥ 10. After dose 1, titers ≥ 40 were present in 79.7% of initially naive subjects and 100% of initially primed subjects, whose respective geometric mean titers were 68 and 1020 (P < 0.001). After dose 2, 100% of subjects had titers ≥ 40, with geometric mean titers increasing to 723 in naive subjects and to 1854 in primed subjects (P < 0.001). Injection site reactions occurred in 56% of subjects after dose 1 and 43% after dose 2 (P < 0.01), with severe reactions noted in ≤ 3%. Fever >39.0°C was infrequent after either dose (5.4%, 6.6%, P = 0.20). Mild or moderate general symptoms were common but short-lived and less frequent after dose 2.

CONCLUSIONS

One dose of adjuvanted vaccine met criteria for licensing seasonal influenza vaccines. A second dose increased titers substantially, potentially affording greater or more durable protection. Adverse effects were common but tolerable. The use of adjuvanted seasonal influenza vaccines in young children merits consideration.

Immunogenicity and safety of AS03-adjuvanted H1N1 pandemic vaccines in children and adolescents

Vaccines with acceptable efficacy profile against the H1N1 A/California/7/2009 virus are needed for use in children. The two studies presented here evaluated the immunogenicity and the reactogenicity/safety of A/H1N1/2009 vaccines containing either 3.75 μg haemagglutinin antigen (HA) and AS03(A)-adjuvant (3.75 μg HA/AS03(A) study) (N=210 [53, 57 and 100 in the 3-5, 6-9 and 10-17 years age strata, respectively]) or 1.9 μg HA and AS03(B)-adjuvant (1.9 μg HA/AS03(B) study) (N=244 [61, 65 and 118 in the 3-5, 6-9 and 10-17 years age strata, respectively]), given as two-dose series. Although the haemagglutination inhibition antibody titres were higher in the 3.75 μg HA/AS03(A) study, both vaccine dosages were highly immunogenic and exceeded regulatory acceptance criteria after the first and the second doses. Seroprotection rates reached 100% and seroconversion rates ranged from 98.2% to 99.1% after each dose of both vaccine dosages. Geometric mean titres increased from 456.5 to 1538.5 and from 297.9 to 1106.7 between the first and the second doses in the 3.75 μg HA/AS03(A) study and the 1.9 μg HA/AS03(B) study, respectively. Despite an observed slight increase of the reactogenicity following the second dose in the 3.75 μg HA/AS03(A) study, the vaccines safety profiles were considered clinically acceptable. In conclusion, both dosages of the AS03-adjuvanted A/H1N1/2009 pandemic influenza vaccines were highly immunogenic and well-tolerated in children and adolescents.

Effect on cellular and humoral immune responses of the AS03 adjuvant system in an A/H1N1/2009 influenza virus vaccine administered to adults during two randomized controlled trials

The influence of AS03(A), a tocopherol oil-in-water emulsion-based adjuvant system, on humoral and cell-mediated responses to A/California/7/2009 H1N1 pandemic vaccine was investigated. In two observer-blind studies, a total of 261 healthy adults aged 18 to 60 years were randomized to receive either AS03(A)-adjuvanted H1N1 vaccine containing 3.75 μg hemagglutinin (HA) or nonadjuvanted H1N1 vaccine containing 15 or 3.75 μg HA on days 0 and 21. Hemagglutination inhibition (HI) antibody and T-cell responses were analyzed up to day 42. A first dose of AS03(A)-adjuvanted vaccine (3.75 μg HA) or nonadjuvanted vaccine (15 μg HA) induced HI responses of similar magnitudes that exceeded licensure criteria (e.g., 94 to 100% with titers of ≥ 40). A lower response following 3.75 μg HA without adjuvant was observed (73% with titers of ≥ 40). Following a second dose, geometric mean HI titers at day 42 were higher for AS03(A)-adjuvanted vaccine (636 and 637) relative to nonadjuvanted vaccine (341 for 15 μg HA and 150 for 3.75 μg HA). Over the 42-day period, the increase in frequency of A/H1N1/2009-specific CD4⁺ T cells was significantly higher in the adjuvanted group than in the nonadjuvanted group. There was no evidence of correlation between baseline CD4⁺ T-cell frequencies and day 21 HI antibody titers, while there was some correlation (R = 0.35) between day 21 CD4⁺ T-cell frequencies and day 42 HI titers. AS03(A) adjuvant enhanced the humoral and CD4⁺ T-cell-mediated responses to A/H1N1/2009 vaccine. Baseline A/H1N1/2009-specific CD4⁺ T-cell frequencies did not predict post-dose 1 antibody responses, but there was some correlation between post-dose 1 CD4⁺ T-cell frequencies and post-dose 2 antibody responses.

Safety review: squalene and thimerosal in vaccines

Few studies show the reluctance of the people to get vaccinated against A (H1N1) influenza for fear of side effects of squalene (MF59, AS03, AF03) and thimerosal. The aim of this paper is to assess the safety in using these adjuvants and preservative reviewing data of clinical trials relative to which formulation includes these compounds. In the current state of knowledge, these vaccines have proved to be effective even though they more frequently give local adverse events than non-adjuvanted influenza vaccines. Systemic side effects are generally not serious. In the studies, adjuvanted vaccines do not increase neither the risk of Guillain Barre syndrome nor auto-immune diseases. There is no convincing evidence that exposure to thimerosal in vaccines had any deletorious effect on physiological outcome.

H5N1 influenza vaccine formulated with AS03 A induces strong cross-reactive and polyfunctional CD4 T-cell responses

Objective

Adjuvantation of an H5N1 split-virion influenza vaccine with AS03_A substantially reduces the antigen dose required to produce a putatively protective humoral response and promotes cross-clade neutralizing responses. We determined the effect of adjuvantation on antibody persistence and B- and T-cell-mediated immune responses.

Methods

Two vaccinations with a split-virion A/Vietnam/1194/2004 (H5N1, clade 1) vaccine containing 3.75–30 μg hemagglutinin and formulated with or without adjuvant were administered to groups of 50 volunteers aged 18–60 years.

Results

Adjuvantation of the vaccine led to better persistence of neutralizing and hemagglutination-inhibiting antibodies and higher frequencies of antigen-specific memory B cells. Cross-reactive and polyfunctional H5N1-specific CD4 T cells were detected at baseline and were amplified by vaccination. Expansion of CD4 T cells was enhanced by adjuvantation.

Conclusion

Formulation of the H5N1 vaccine with AS03_A enhances antibody persistence and induces stronger T- and B-cell responses. The cross-clade T-cell immunity indicates that the adjuvanted vaccine primes individuals to respond to either infection and/or subsequent vaccination with strains drifted from the primary vaccine strain.

A phase II, open-label, multicentre study to evaluate the immunogenicity and safety of an adjuvanted prepandemic (H5N1) influenza vaccine in healthy Japanese adults

Background

Promising clinical data and significant antigen-sparing have been demonstrated for a pandemic H5N1 influenza split-virion vaccine adjuvanted with AS03_A, an α-tocopherol-containing oil-in-water emulsion-based Adjuvant System. Although studies using this formulation have been reported, there have been no data for Japanese populations. This study therefore aimed to assess the immunogenicity and tolerability of a prepandemic (H5N1) influenza vaccine adjuvanted with AS03_A in Japanese adults.

Methods

This open-label, single-group study was conducted at two centres in Japan in healthy Japanese males and females aged 20-64 years (n = 100). Subjects received two doses of vaccine, containing 3.75 μg haemagglutinin of the A/Indonesia/5/2005-like IBCDC-RG2 Clade 2.1 (H5N1) strain adjuvanted with AS03_A, 21 days apart. The primary endpoint evaluated the humoral immune response in terms of H5N1 haemagglutination inhibition (HI) antibody titres against the vaccine strain (Clade 2.1) 21 days after the second dose. Ninety five percent confidence intervals for geometric mean titres, seroprotection, seroconversion and seropositivity rates were calculated. Secondary and exploratory endpoints included the assessment of the humoral response in terms of neutralising antibody titres, the response against additional H5N1 strains (Clade 1 and Clade 2.2), as well as the evaluation of safety and reactogenicity.

Results

Robust immune responses were elicited after two doses of the prepandemic influenza vaccine adjuvanted with AS03_A. Overall, vaccine HI seroconversion rates and seroprotection rates were 91% 21 days after the second vaccination. This fulfilled all regulatory acceptance criteria for the vaccine-homologous HI antibody level. A substantial cross-reactive humoral immune response was also observed against the virus strains A/turkey/Turkey/1/2005 (Clade 2.2) and A/Vietnam/1194/2004 (Clade 1) after the second vaccine administration. A marked post-vaccination response in terms of neutralising antibody titres was demonstrated and persistence of the immune response was observed 6 months after the first dose. The vaccine was generally well tolerated and there were no serious adverse events reported.

Conclusions

The H5N1 candidate vaccine adjuvanted with AS03_A elicited a strong and persistent immune response against the vaccine strain A/Indonesia/5/2005 in Japanese adults. Vaccination with this formulation demonstrated a clinically acceptable reactogenicity profile and did not raise any safety concerns in this population.

Trial registration

Clinicaltrials.gov NCT00742885

Unmet needs in modern vaccinology: adjuvants to improve the immune response

The key objective of vaccination is the induction of an effective pathogen-specific immune response that leads to protection against infection and/or disease caused by that pathogen, and that may ultimately result in its eradication from humanity. The concept that the immune response to pathogen antigens can be improved by the addition of certain compounds into the vaccine formulation was demonstrated about one hundred years ago when aluminium salts were introduced. New vaccine technology has led to vaccines containing highly purified antigens with improved tolerability and safety profiles, but the immune response they induce is suboptimal without the help of adjuvants. In parallel, the development of effective vaccines has been facing more and more important challenges linked to complicated pathogens (e.g. malaria, TB, HIV, etc.) and/or to subjects with conditions that jeopardize the induction or persistence of a protective immune response. A greater understanding of innate and adaptive immunity and their close interaction at the molecular level is yielding insights into the possibility of selectively stimulating immunological pathways to obtain the desired immune response. The better understanding of the mechanism of 'immunogenicity' and 'adjuvanticity' has prompted the research of new vaccine design based on new technologies, such as naked DNA or live vector vaccines and the new adjuvant approaches. Adjuvants can be used to enhance the magnitude and affect the type of the antigen-specific immune response, and the combination of antigens with more than one adjuvant, the so called adjuvant system approach, has been shown to allow the development of vaccines with the ability to generate effective immune responses adapted to both the pathogen and the target population. This review focuses on the adjuvants and adjuvant systems currently in use in vaccines, future applications, and the remaining challenges the field is facing.