Immunogenicity and safety in adults of one dose of influenza A H1N1v 2009 vaccine formulated with and without AS03A-adjuvant: Preliminary report of an observer-blind,randomised trial

Governments and public health officials are preparing vaccination campaigns against the 2009 influenza A H1N1v pandemic strain. We evaluated two inactivated split-virion A/California/7/2009 H1N1v pandemic vaccines formulated with/without AS03_A, an oil-in-water emulsion adjuvant system containing tocopherol.     

Immunogenicity and safety of AS03A-adjuvanted H5N1 influenza vaccine prepared from bulk antigen after stockpiling for 4 years

BackgroundStockpiling vaccine for deployment in the event of an influenza pandemic is an important mitigation strategy. A necessary aspect of stockpiling is to determine the shelf-life of the stored vaccine.MethodsIn this Phase II, open-label study we assessed the immunogenicity and safety of H5N1 A/Indonesia/5/2005 vaccine adjuvanted with AS03_A. The AS03_A-H5N1 vaccine was prepared from bulk antigen that had been stored for 4 years, and adjuvant that had been stored for 2.5 years. Both the antigen and adjuvant were filled in separate multi-dose vials within 4 months of use, and on the day of vaccination, the contents of antigen and adjuvant vials were mixed. Seventy-eight adults aged 18–64 years were scheduled to receive two doses of hemagglutinin-antigen (3.75 μg) given 21 days apart. Antibody responses were assessed by hemagglutination-inhibition (HI) assay according to age (18–30 years, 31–40 years, 41–50 years, and 51–64 years). Reactogenicity was assessed for 7 days after each vaccination, and safety was assessed for 385 days post-vaccination (NCT01416571).ResultsThe vaccine was immunogenic. Twenty-one days after the second dose of vaccine in the overall population, the HI seroconversion rate and seroprotection rate (SPR; titer ≥1:40) was 96.0% and 98.7%, respectively. At Day 182 after vaccination, the SPR was 76.7% in the overall population. Injection site pain was the most frequent solicited adverse event (91.0%), and no safety concerns were raised.ConclusionThe immunogenicity and safety observed with AS03_A-H5N1 vaccine formulated with bulk antigen which had been stockpiled before vialing and administration was consistent with that previously observed with newly manufactured AS03_A-H5N1 vaccine. This suggests that stockpiling bulk antigen for 4 years does not compromise the immunogenicity or reactogenicity of the vaccine.     

Immunogenicity and safety of an AS03-adjuvanted H7N1 vaccine in adults 65 years of age and older: A phase II,observer-blind,randomized, controlled trial

BackgroundH7 influenza strains can cause severe and often fatal human infections, especially in the elderly. This phase II, observer-blind, randomized trial (www.ClinicalTrials.gov: NCT01949090) assessed the immunogenicity and safety of a novel AS03-adjuvanted H7N1 vaccine that may serve as a model H7-subtype vaccine.Methods360 adults ≥65 years of age in stable health received either 1 of 4 adjuvanted A/mallard/Netherlands/12/2000 split virion vaccine formulations (3.75 μg or 7.5 μg hemagglutinin adjuvanted with either AS03_A or AS03_B) or saline placebo, given as a 2-dose series. Immunogenicity was assessed using hemagglutination-inhibition (HI) and microneutralization (MN) assays for the per-protocol cohort, comprising 332 participants at 21 days post-each dose, 332 at month 6, and 309 at month 12 (HI assay only). Safety was assessed up to month 12 for all participants who had received ≥1 dose (360 participants).ResultsFor H7N1 HI antibody assessment at day 42 (21 days post-dose 2), seroprotection rates (SPR) in the vaccinated groups were 69.6%–88.7%, seroconversion rates (SCR) 69.6%–88.5%, mean geometric increase (MGI) 11.0–18.9, and HI geometric mean titers (GMTs) 55.0–104.8. These parameters declined by month 6 and month 12. Microneutralization GMTs were 46.2–74.7 in the vaccinated groups at day 42, while vaccine response rate (VRR; proportion with ≥4-fold increase in MN titer) was 46.4%–81.5%. For the cross-reactive H7N9 strain, at day 42, HI GMT were 64.3–201.3, SPR 78.6%–96.3%, SCR 79.3%–96.3%, and MGI 14.1–37.7; MN GMTs were 44.0–85.6, and VRR 46.4–85.2%.The most frequent solicited symptom was injection site pain (41.7%–65.0% of vaccine recipients). In total, 40 participants reported 67 serious adverse events; none were considered causally related to vaccination.ConclusionsIn adults aged ≥65 years, the adjuvanted H7N1 vaccine was immunogenic after 2 doses, and had an acceptable safety profile.www.ClinicalTrials.gov: NCT01949090.     

Safety and immunogenicity of an inactivated cell culture-derived H7N9 influenza vaccine in healthy adults: A phase I/II,prospective, randomized,open-label trial

BackgroundWe conducted a phase I/II clinical trial to evaluate the safety and immunogenicity of a Madin-Darby canine kidney (MDCK) cell-grown inactivated H7N9 influenza vaccine for pandemic preparedness purposes.MethodsBetween April 7, 2015 and May 27, 2016, healthy adults aged 20–60 years were enrolled sequentially in phase I (n = 40) and phase II (n = 160) from three hospitals in Taiwan and randomized to receive 2 doses of whole-virus H7N9 vaccine (15 or 30 μg hemagglutinin antigen (HA) with or without an aluminum hydroxide adjuvant) at 21-day intervals. Safety up to 180 days and changes in hemagglutinin inhibition (HI) titers at 21 days after each vaccination were determined.ResultsOf the 200 randomized subjects, 193 (96.5%) received 2 doses of the study vaccine and were included in the intention-to-treat analysis for safety, and 190 (95%) were included in the per-protocol analysis for immunogenicity. Most adverse events were mild and transient; no death or vaccine-related serious adverse events were reported. Overall, higher immune responses were observed in the groups administered with 30 μg HA formulation than in the other two groups administered with 15 μg HA formulation. The highest immune response was observed in subjects who received 2 doses of the adjuvanted vaccine containing 30 μg HA with HI titer, seroprotection rate, seroconversion rate, and seroconversion factor of 36.2, 64.6%, 64.6% and 5.7, respectively.ConclusionsOur study demonstrated that the H7N9 influenza vaccine containing 30 µg HA with aluminum hydroxide adjuvant was immunogenic and safe in adults aged 20–60 years.CLINICALTRIALS.GOV identifier: NCT02436928.     

Immunogenicity and safety of different dose schedules and antigen doses of an MF59-adjuvanted H7N9 vaccine in healthy adults aged 65 years and older

BackgroundThe number of human influenza A (H7N9) infections has escalated since 2013 with high resultant mortality. We conducted a phase II, randomized, partially-blinded trial to evaluate the safety and immunogenicity of an MF59-adjuvanted inactivated, split virion, H7N9 influenza vaccine (H7N9 IIV) administered at various dose levels and schedules in older adults.Methods479 adults ≥ 65 years of age in stable health were randomized to one of six groups to receive either 3.75, 7.5 or 15 µg of influenza A/Shanghai/02/2013 (H7N9) IIV adjuvanted with MF59 given as a 3-dose series either on days 1, 28 and 168 or on days 1, 57 and 168. Immunogenicity was assessed using both hemagglutination inhibition (HAI) and microneutralization (MN) assays prior to and 28 days following each dose. Safety was assessed through 1 year following the last dose.ResultsSubjects in all groups had only modest immune responses, with the HAI GMT < 20 after the second vaccine dose and <29 after the third vaccine dose. HAI titers ≥ 40 were seen in <37% of subjects after the second dose and <49% after the third dose. There were no significant differences seen between the two dose schedules. MN titers followed similar patterns, although the titers were approximately two-fold higher than the HAI titers. Logistic regression modeling demonstrated no statistically significant associations between the immune responses and age, sex or body mass index whereas recent prior receipt of seasonal influenza vaccine significantly reduced the HAI response [OR 0.13 (95% CI 0.05, 0.33); p < 0.001]. Overall, the vaccine was well tolerated. Two mild potentially immune mediated adverse events occurred, lichen planus and guttate psoriasis.ConclusionsMF59-adjuvanted H7N9 IIV was only modestly immunogenic in the older adult population following three doses. There were no significant differences in antibody responses noted among the various antigen doses or the two dose schedules.     

A clinical phase I study of an EB66 cell-derived H5N1 pandemic vaccine adjuvanted with AS03

BackgroundWe conducted a phase I clinical trial of a cell culture-derived AS03-adjuvanted influenza vaccine containing HA antigen (A/Indonesia/05/2005(H5N1)/PR8-IBCDC-RG2) derived from EB66 cells (KD-295).MethodsHealthy male adult volunteers (20–40 years old, N = 60) enrolled in the study were divided into 3 groups, the MA group (3.8 μg of HA + AS03), HA group (7.5 μg of HA + AS03), and 1/2 MA group (half the volume of the MA group), and received KD-295 intramuscularly twice with a 21-day interval. After administration of KD-295, adverse events, clinical laboratory parameters, and immune response to the vaccine strain and heterologous virus strains were evaluated.ResultsNo severe adverse events leading to discontinuation of vaccine administration occurred. The vaccine was well-tolerated. There was no dose dependency in the rate, timing, or duration of the adverse events. Immunogenicity of the vaccines was evaluated by HI (hemagglutination inhibition) assay, which confirmed that the antibody response to the vaccine strain and heterologous strain in all groups met the three criteria for immunogenicity described in the Japanese guidelines for development of a pandemic prototype vaccine. We also measured the neutralizing antibody titers against several virus strains, and confirmed a significant rise in antibody levels to both the vaccine strain and heterologous strains.ConclusionThe EB66-derived H5N1 influenza vaccine adjuvanted with AS03 elicited a broad cross-reactive antibody response among H5N1 strains with acceptable reactogenicity. Therefore, KD-295 can be considered a useful pandemic and pre-pandemic influenza vaccine candidate.     

Immune response after one or two doses of pandemic influenza A (H1N1) monovalent,AS03-adjuvanted vaccine in HIV infected adults

Introduction

Continued research is needed to evaluate and improve the immunogenicity of influenza vaccines in HIV infected patients. We aimed to determine the antibody responses after one or two doses of the AS03-adjuvanted pandemic influenza A (H1N1) vaccine in HIV infected patients.

Method

Following the influenza season 2009/2010, 219 HIV infected patients were included and divided into three groups depending on whether they received none (n = 60), one (n = 31) or two (n = 128) doses of pandemic influenza A (H1N1) vaccine. At inclusion, antibody titers for all patients were analyzed and compared to pre-pandemic antibody titers analyzed from serum samples in a local storage facility.

Results

4–9 months after a single immunization, we found a seroprotection rate of 77.4% and seroconversion rate of 67.7%. After two immunizations the rates increased significantly to seroprotection rate of 97.7% and seroconversion rate of 86.7%.

Conclusion

A single dose of AS03-adjuvanted pandemic influenza A (H1N1) vaccine created an adequate immune response in HIV infected patients lasting as long as 4–9 months. Two doses improved the immunogenicity further.     

Efficacy of an AS03A-adjuvanted split H5N1 influenza vaccine against an antigenically distinct low pathogenic H5N1 virus in pigs

We used the pig model of influenza to examine the efficacy of an AS03(A)-adjuvanted split H5N1 (A/Indonesia/05/2005) vaccine against challenge with a low pathogenic (LP) H5N1 avian influenza (AI) virus (duck/Minnesota/1525/1981) with only 85% amino acid homology in its HA1. Influenza seronegative pigs were vaccinated twice intramuscularly with adjuvanted vaccine at 3 antigen doses, unadjuvanted vaccine or placebo. All pigs were challenged 4 weeks after the second vaccination and euthanized 2 days later. After 2 vaccinations, all pigs in the adjuvanted vaccine groups had high hemagglutination inhibiting (HI) antibody titers to the vaccine strain (160-640), and lower antibody titers to the A/Vietnam/1194/04 H5N1 strain and to 2 LP H5 viruses with 90-91% amino acid homology to the vaccine strain (20-160). Eight out of 12 pigs had HI titers (10-20) to the challenge virus immediately before challenge. Neuraminidase inhibiting antibodies to the challenge virus were detected in most pigs (7/12) and virus neutralizing antibodies in all pigs. There was no antigen-dose dependent effect on the antibody response among the pigs immunized with adjuvanted H5N1 vaccines. After challenge, these pigs showed a complete clinical protection, reduced lung lesions and a significant protection against virus replication in the respiratory tract. Though the challenge virus showed only moderate replication efficiency in pigs, our study suggests that AS03(A)-adjuvanted H5N1 vaccine may confer a broader protection than generally assumed. The pros and cons of the pig as an H5N1 challenge model are also discussed.     

Squalene-adjuvanted H7N9 virus vaccine induces robust humoral immune response against H7N9 and H7N7 viruses

Recent cases of avian influenza H7N9 have caused great concerns that virus may become transmittable between humans. It is imperative to develop an effective vaccine to fight against the pandemic potential of this H7N9 influenza virus to protect human from the disease. This study aims to investigate an optimized formulation for the development of H7N9 vaccines. Various doses of H7N9 inactivated whole or split-virus antigens (0.5, 1.5, or 3 μg based on hemagglutinin content) combined with squalene-based adjuvant (AddaVAX), aluminum hydroxide Al(OH)₃ or without adjuvant were evaluated for the efficacy of H7N9 vaccine regiments in mice. With either H7N9 whole or split-virus based vaccines, AddaVAX-adjuvanted formulations were the most immunogenic in eliciting significant humoral immune response against H7N9 virus and exhibited strong cross-reactive response in hemagglutination inhibition (HAI) and viral-neutralization assays against H7N7 virus as well. In contrast, formulations with Al(OH)₃ or without adjuvant were less immunogenic and elicited lower titers of HAI and microneutralization assays against both viruses. Dose-sparing experiments suggested that the formulation with as low as 0.004 μg of split or whole virus vaccine antigens together with 50% AddaVAX provided sufficient sero-protective HAI titers and achieved essential virus-neutralizing antibody titers against H7-subtype influenza viruses in mice. Protection experiments demonstrated that the formulation of 0.004 μg to 0.5 μg of split-virion vaccines with AddaVAX conferred full protection against viral challenge up to 100 LD50 of wild-type H7N9 virus, with 0% survival in placebo group. Taken together, our study demonstrates that squalene-based adjuvant can significantly enhance the protective efficacy of H7N9 virus vaccine and provides a useful strategy to confront the potential pandemic outbreaks of H7N9 virus.     

A phase I evaluation of inactivated influenza A/H5N1 vaccine administered by the intradermal or the intramuscular route

In a phase I clinical trial, one hundred healthy young adults were randomized to receive two doses 28 days apart of an inactivated, subvirion vaccine containing 15 or 45 μg of influenza A/H5N1 hemagglutinin (HA) by the intramuscular (IM) route, or 3 or 9 μg of H5 HA by the intradermal(ID) route. Seventy-seven subjects received a third dose. All regimens were safe and well tolerated. Antibody responses after two or three doses were low (≤20% or ≤38%, respectively) and similar in groups given 3 or 9 μg ID or 15 μg IM, and were significantly lower than those given 45 μg IM. Higher dosages of H5 HA and/or inclusion of adjuvant will be required to enhance immunogenicity by the ID route.     

Lessons from pandemic influenza A(H1N1): the research-based vaccine industry's perspective

As A(H1N1) influenza enters the post-pandemic phase, health authorities around the world are reviewing the response to the pandemic. To ensure this process enhances future preparations, it is essential that perspectives are included from all relevant stakeholders, including vaccine manufacturers. This paper outlines the contribution of R&D-based influenza vaccine producers to the pandemic response, and explores lessons that can be learned to improve future preparedness.The emergence of 2009 A(H1N1) influenza led to unprecedented collaboration between global health authorities, scientists and manufacturers, resulting in the most comprehensive pandemic response ever undertaken, with a number of vaccines approved for use three months after the pandemic declaration. This response was only possible because of the extensive preparations undertaken during the last decade.During this period, manufacturers greatly increased influenza vaccine production capacity, and estimates suggest a further doubling of capacity by 2014. Producers also introduced cell-culture technology, while adjuvant and whole virion technologies significantly reduced pandemic vaccine antigen content. This substantially increased pandemic vaccine production capacity, which in July 2009 WHO estimated reached 4.9 billion doses per annum. Manufacturers also worked with health authorities to establish risk management plans for robust vaccine surveillance during the pandemic. Individual producers pledged significant donations of vaccine doses and tiered-pricing approaches for developing country supply.Based on the pandemic experience, a number of improvements would strengthen future preparedness. Technical improvements to rapidly select optimal vaccine viruses, and processes to speed up vaccine standardization, could accelerate and extend vaccine availability. Establishing vaccine supply agreements beforehand would avoid the need for complex discussions during a period of intense time pressure.Enhancing international regulatory co-operation and mutual recognition of approvals could accelerate vaccine supply, while maintaining safety standards. Strengthening communications with the public and healthcare workers using new approaches and new channels could help improve vaccine uptake. Finally, increasing seasonal vaccine coverage will be particularly important to extend and sustain pandemic vaccine production capacity.     

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

BackgroundAS03-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.MethodsThis Phase IV, randomized, study was conducted to assess the immunogenicity, reactogenicity, and safety of two doses (3.75 μg 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).ResultsAS03-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.ConclusionThe results indicate that AS03-H5N1 vaccine is immunogenic with reactogenicity and safety findings that are consistent with the established profile of AS03-H5N1 vaccine.     

AF03-adjuvanted and non-adjuvanted pandemic influenza A (H1N1) 2009 vaccines induce strong antibody responses in seasonal influenza vaccine-primed and unprimed mice

Pandemic influenza vaccines have been manufactured using the A/California/07/2009 (H1N1) strain as recommended by the World Health Organization. We evaluated in mice the immunogenicity of pandemic (H1N1) 2009 vaccine and the impact of prior vaccination against seasonal trivalent influenza vaccines (TIV) on antibody responses against pandemic (H1N1) 2009. In naïve mice, a single dose of unadjuvanted H1N1 vaccine (3 μg of HA) was shown to elicit hemagglutination inhibition (HI) antibody titers >40, a titer associated with protection in humans against seasonal influenza. A second vaccine dose of pandemic (H1N1) 2009 vaccine strongly increased these titers, which were consistently higher in mice previously primed with TIV than in naïve mice. At a low immunization dose (0.3 μg of HA), the AF03-adjuvanted vaccine elicited higher HI antibody titers than the corresponding unadjuvanted vaccines in both naïve and TIV-primed animals, suggesting a potential for antigen dose-sparing. These results are in accordance with the use in humans of a split-virion inactivated pandemic (H1N1) 2009 vaccine formulated with or without AF03 adjuvant to protect children and young adults against influenza A (H1N1) 2009 infection.     

Delayed focal lipoatrophy after AS03-adjuvanted influenza A (H1N1) 2009 vaccine

Intramuscular vaccination may lead to loss of subcutaneous fat resulting in skin depression at the site of injection. We report for the first time a delayed lipoatrophy after with AS03-adjuvanted influenza A (H1N1) 2009 vaccine. Inadequate administration into the adipose tissue may be causative. During next pandemic, education to optimal intramuscular administration and prolonged monitoring of adverse effects could be proposed.     

Clinical testing of an inactivated influenza A/H5N1 vaccine candidate in a double-blinded,placebo-controlled,randomized trial in healthy adults in Vietnam

We tested an inactivated egg-grown whole virus influenza A/H5N1 vaccine candidate developed by the Institute of Vaccines and Medical Biologicals (IVAC), a state-run vaccine manufacturer in Vietnam, in a Phase 1, placebo controlled, double blinded, randomized trial. The vaccine was adjuvanted with aluminum hydroxide. The trial enrolled 75 subjects who were randomized to receive two injections of one of the following: low-dose of vaccine (7.5 mcg HA), high-dose of vaccine (15 mcg HA), or placebo. The vaccine candidate was well tolerated with minimal local reactogenicity consisting of mild, short-lived injection site pain and/or tenderness. No systemic reactogenicity was observed other than transient low-grade fever in about 13% of the subjects and no unsolicited adverse events were attributable to product administration. Immune responses were assessed at baseline and after the first and second dose by hemagglutination inhibition (HAI) and microneutralization (MN) assays, with 72% of the high-dose and 68% of the low-dose vaccine recipients presenting a ⩾4-fold response in the HAI assay and 72% of the high-dose and 61% of the low-dose vaccine recipients exhibiting a ⩾4-fold response in the MN assay. These promising results support further development. ClinicalTrials.gov number NCT02171819, June 20, 2014.     

Safety and immunogenicity of a virus-like particle pandemic influenza A (H1N1) 2009 vaccine in a blinded, randomized, placebo-controlled trial of adults in Mexico

Virus-like particles (VLPs) can be rapidly developed from influenza virus genetic sequences in order to supply vaccine after the onset of a pandemic. The safety and immunogenicity of one or two doses of a recombinant A (H1N1) 2009 influenza VLP vaccine was evaluated in a two-stage, Phase 2, randomized, double-blind, placebo-controlled study conducted in 4563 healthy adults, 18-64 years of age, during the H1N1 2009 pandemic in Mexico. In Part A, 1013 subjects were randomized into four treatment groups (5 μg, 15 μg, or 45 μg hemagglutinin [HA] VLP vaccine or placebo) and vaccinated 21 days apart, with sera collected on Days 1, 14 and 36 for hemagglutination inhibition (HAI) testing. After review of safety and immunogenicity data from Part A, additional subjects were immunized with a single dose of 15 μg VLP vaccine (N = 2537) or placebo (N = 1011) and assessed for safety in Part B. Results showed the H1N1 2009 VLP vaccine was safe and well-tolerated. Systemic solicited events were similar between placebo and VLP vaccinated groups with no vaccine-related serious adverse events. Dose response trends for solicited local adverse events were observed, with higher incidences of local pain, swelling, tenderness, and redness reported in the higher VLP dose groups (15 μg and 45 μg) compared to the placebo and 5 μg VLP groups following both vaccinations. Although the majority of local AEs were mild in severity, a dose trend in events of moderate or greater severity was also noted for these solicited events. The VLP vaccine groups demonstrated robust HAI immune responses after a single vaccination, with high rates of seroprotection (≥40 HAI titer) in 82-92% of all subjects and in 64-85% of subjects who were seronegative at the time of immunization. HAI geometric mean titers (GMTs), geometric mean ratios (GMRs) and seroconversion rates were also all statistically higher in the VLP groups compared to placebo for both post-baseline time points. Based on these data, additional clinical trials are in development to evaluate influenza vaccine candidate antigens manufactured using Spodoptera frugiperda (Sf9)/baculovirus-based VLP technology.     

Safety and immunogenicity of an inactivated split-virus influenza A/H1N1 vaccine in healthy children from 6 months to <18 years of age: A prospective,open-label,multi-center trial

This study was conducted to determine the immunogenicity and safety of an inactivated split-virus influenza A/H1N1 vaccine in healthy Korean children from 6 months to <18 years of age. The immunization schedule consisted of two vaccinations, 21 days apart. The unadjuvanted vaccine contained 7.5 μg (subjects 6 months to <3 years of age) or 15 μg (subjects 3 to <18 years of age) of hemagglutinin antigen per dose. A total of 251 subjects were enrolled and 248 and 242 subjects, respectively, were included in the post-first dose and post-second dose immunogenicity evaluations conducted on a per protocol basis. By day 21, after the first dose, hemagglutination-inhibition titers of 1:40 or more were observed in 5.9% of subjects 6 months to <3 years of age, 34.9% of subjects 3 to <9 years of age and 81.4% of subjects 9–18 years of age. By day 21 after the second dose, the titer had been achieved 55.9%, 69.5% and 90.5%, respectively. No vaccination-related serious adverse events were observed. A single 15-μg dose of vaccine was highly immunogenic in subjects equal to or more than 9 years of age. However, a two-dose regimen is needed to produce potentially protective antibody titers in younger children.     

The humoral immune response of hematopoietic stem cell transplantation recipients to AS03-adjuvanted A/California/7/2009 (H1N1)v-like virus vaccine during the 2009 pandemic

We evaluated the formation of hemagglutination-inhibition (HI) antibodies in response to vaccination of 55 allogeneic and 23 autologous hematopoietic stem cell transplantation (HSCT) recipients with 3.75 μg inactivated influenza A/California/7/2009 (H1N1)v-like virus adjuvanted with AS03, given towards the end of the 2009 influenza pandemic. The 78 HSCT recipients, aged 11-72 (median 50) years, were vaccinated 1-290 (median 27) months post-HSCT. Of the 55 allogeneic HSCT recipients, 50.9% received reduced intensity conditioning, 74.5% had a sibling donor, 67.2% had active graft-versus-host disease and 43.6% were on steroid therapy. At baseline, 14/78 (17.9%) had HI titers ≥1:40. Blood samples of 77 patients were available post-1st vaccination; of these, 34 (44.2%) patients had HI titers ≥1:40. Blood samples of 43 patients were available post-2nd vaccination; of these, 21 (48.8%) had HI titers ≥1:40. There was a significant increase in HI titers ≥1:40 from baseline to both post-1st and 2nd vaccinations (p < 0.001 each), and also from 1st to 2nd vaccination (p = 0.008). In seronegative (HI titers <1:10) patients, whose sera were available before, after one dose, and after 2 doses of vaccine, seroconversion (to ≥1:40) occurred in 4/24 (16.7%) after 1-dose and in a total of 10/24 (41.7%) after 2-dose vaccination (p = 0.031). Logistic regression analysis revealed that ≥1:40 HI titers were significantly associated with higher lymphocyte counts and higher HI baseline titers and, in allogeneic HSCT, with having a sibling donor and higher baseline titers. In conclusion, 2-dose vaccination with AS03-adjuvanted vaccine containing 3.75 μg antigen resulted in a statistically significant, yet limited, serological response. Therefore, additional precautions should be taken during influenza outbreaks.