H1N1pdm09 Vaccine Research Articles

Evaluation of the Effectiveness of Pandemic Influenza A(H1N1) 2009 Vaccine Based on an Outbreak Investigation During the 2010–2011 Season in Korean Military Camps

ObjectivesIn December 2010, there was an outbreak of acute febrile respiratory disease in many Korean military camps that were not geographically related. A laboratory analysis confirmed a number of these cases to be infected by the pandemic influenza A(H1N1) 2009 (H1N1pdm09) virus. Because mass vaccination against H1N1pdm09 was implemented at the infected military camps eleven months ago, the outbreak areas in which both vaccinated and nonvaccinated individuals were well mixed, gave us an opportunity to evaluate the effectiveness of H1N1pdm09 vaccine through a retrospective cohort study design. MethodsA self-administered questionnaire was distributed to the three military camps in which the outbreak occurred for case detection, determination of vaccination status, and characterization of other risk factors. The overall response rate was 86.8% (395/455). Case was defined as fever (≥38 °C) with cough or sore throat, influenza-like illness (ILI), and vaccination status verified by vaccination registry. Crude vaccine effectiveness (VE) was calculated as “1 − attack rate in vaccinated individuals/attack rate in nonvaccinated individuals”, and adjusted VE was calculated as “1 – odds ratio” using logistic regression adjusted for potential confounding factor. A number of ILI definitions were used to test the robustness of the result. ResultsThe attack rate of ILI was 12.8% in register-verified vaccinated individuals and 24.0% in nonvaccinated individuals. The crude VE was thus calculated to be 46.8% [95% confidence interval (CI): 14.5–66.9]. The adjusted VE rate was 46.8% (95% CI: –9.4 to 74.1). Various combinations of ILI symptoms also showed similar VE rates. ConclusionWe evaluated the effectiveness of H1N1pdm09 vaccine in the 2010–2011 season in an outbreak setting. Although the result was not sensitive to any analytical method used and ILI case definition, the magnitude of effectiveness was lower than estimated in the 2009–2010 season.

Live attenuated seasonal and pandemic influenza vaccine in school-age children: A randomized controlled trial

BackgroundThe novel influenza A(H1N1pdm09) virus emerged in North America in early 2009 and rapidly spread worldwide. In this study we report the efficacy of the live attenuated monovalent H1N1pdm09 vaccine and 2009–10 seasonal influenza vaccine in a randomized double-blind placebo-controlled trial. MethodsWe enrolled 703 children aged 7–11. Each child was randomly allocated in the ratio 3:2 to receive one dose of live attenuated monovalent H1N1pdm09 vaccine or saline placebo between November 2009 and January 2010, followed after 3–10 weeks by independent random allocation to one dose of live attenuated trivalent 2009–10 seasonal influenza vaccine or saline placebo in the same ratio. Children were followed up through September 2010 with biweekly telephone calls and symptom diaries. Seasonal and pandemic influenza infections were confirmed by virologic testing of nose and throat swabs collected during acute respiratory illnesses. ResultsOverall, 30 children had confirmed influenza including 3 (0.43%) H1N1pdm09, 10 (1.4%) seasonal A(H3N2), and 17 (2.4%) influenza B. There were no significant differences in incidence rates of H1N1pdm09 or A(H3N2) between the four study arms, but receipt of the seasonal influenza vaccine was associated with a significant reduction in risk of influenza B (p<0.01). Vaccine efficacy against confirmed H1N1pdm09 infection associated with receipt of the monovalent H1N1pdm09 vaccine was 65% (95% confidence interval, CI: −281%, 97%). Vaccine efficacies against confirmed seasonal influenza A(H3N2) and B infection associated with receipt of the seasonal influenza vaccine were 31% (95% CI: −138%, 80%) and 96% (95% CI: 67%, 99%) respectively. ConclusionsVaccine efficacy was consistent with other studies of the monovalent H1N1pdm09 vaccine and seasonal influenza vaccines. Our study was underpowered to provide precise estimates of vaccine efficacy due to low incidence of influenza A viruses during the study period.

Safety and immunogenicity of 2010–2011 A/H1N1pdm09-containing trivalent inactivated influenza vaccine in adults previously given AS03-adjuvanted H1N1 2009 pandemic vaccine

Many Canadians received a novel AS03-adjuvanted vaccine during the 2009 influenza A/H1N1 pandemic. Longer term implications of adjuvant use were unclear: would anti-H1N1 immune responses persist at high levels and, if so, could that result in increased or unusual adverse effects upon re-exposure to H1N1pdm09 antigen in the trivalent influenza vaccine (TIV) for 2010–11? To answer these questions, adults given AS03-adjuvanted H1N1pdm09 vaccine (Arepanrix®, GSK Canada) 9–10 mo earlier were enrolled in an evaluator-blinded, crossover trial to receive 2010–2011 non-adjuvanted TIV (Fluviral®, GSK Canada) and placebo 10 d apart, in random order. Adverse effects were monitored for 7 d after each injection. Vaccine-attributable adverse event (VAAE) rates were calculated by subtracting rates after placebo from those after vaccine. Blood was obtained pre-vaccination and 21–30 d afterward to measure hemagglutination inhibiting antibody titers. In total, 326 participants were enrolled and 321 completed the study. VAAE rates were low except for myalgia (18.6%) and injection site pain (63.2%). At baseline, H1N1pdm09 titers ≥ 40 were present in 176/325 subjects (54.2%, 95% confidence interval 48.6, 59.7), with a geometric mean titer (GMT) of 37.4 (95% CI 32.8, 42.6). Post-immunization, 96.0% (95% CI 92.3, 97.8) had H1N1pdm09 titers ≥ 40, with GMT of 167.4 (95% CI 148.7, 188.5). Responses to both influenza A strains in TIV were similar, implying no lasting effect of adjuvant exposure. In summary, titers ≥ 40 persisted in only half the participants 9–10 mo after adjuvanted pandemic vaccine but were restored in nearly all after TIV vaccination, with minimal increase in adverse effects.

AID Activity in B Cells Strongly Correlates with Polyclonal Antibody Affinity Maturation in-vivo Following Pandemic 2009-H1N1 Vaccination in Humans

The role of Activation-Induced Cytidine Deaminase (AID) in somatic hypermutation and polyclonal antibody affinity maturation has not been shown for polyclonal responses in humans. We investigated whether AID induction in human B cells following H1N1pdm09 vaccination correlated with in-vivo antibody affinity maturation against hemagglutinin domains in plasma of young and elderly individuals. AID was measured by qPCR in B cells from individuals of different ages immunized with the H1N1pdm09 influenza vaccine. Polyclonal antibody affinity in human plasma for the HA1 and HA2 domains of the H1N1pdm09 hemagglutinin was measured by antibody-antigen complex dissociation rates using real time kinetics in Surface Plasmon Resonance. Results show an age-related decrease in AID induction in B cells following H1N1pdm09 vaccination. Levels of AID mRNA before vaccination and fold-increase of AID mRNA expression after H1N1pdm09 vaccination directly correlated with increase in polyclonal antibody affinity to the HA1 globular domain (but not to the conserved HA2 stalk). In the younger population, significant affinity maturation to the HA1 globular domain was observed, which associated with initial levels of AID and fold-increase in AID after vaccination. In some older individuals (>65 yr), higher affinity to the HA1 domain was observed before vaccination and H1N1pdm09 vaccination resulted in minimal change in antibody affinity, which correlated with low AID induction in this age group. These findings demonstrate for the first time a strong correlation between AID induction and in-vivo antibody affinity maturation in humans. The ability to generate high affinity antibodies could have significant impact on the elucidation of age-specific antibody responses following vaccination and eventual clinical efficacy and disease outcome.

H1N1pdm09 Adjuvanted Vaccination in HIV-Infected Adults: A Randomized Trial of Two Single versus Two Double Doses

BackgroundSince human immunodeficiency virus (HIV)-infected individuals are at increased risk of severe disease from pandemic influenza A (H1N1pdm09), vaccination was recommended as a prevention strategy. The aim of the present study was to evaluate the safety, immunogenicity and persistence of the immune response after vaccination against pandemic influenza A (H1N1pdm09) with an adjuvanted vaccine in human immunodeficiency virus (HIV)-infected adults using two single and two double doses.Methodology/Principal FindingsOpen label, randomized trial to evaluate the immune response following H1N1pdm09 vaccination in HIV-infected participants compared to HIV-negative controls (NCT01155037). HIV-infected participants were randomized to receive 2 single (3.75 µg hemagglutinin) or 2 double (7.5 µg hemagglutinin) doses of the vaccine, 21 days apart. Controls received one dose of the vaccine. The primary endpoint was seroconversion as measured by hemagglutination inhibition assay. Two hundred fifty six HIV-infected participants (129 and 127 randomized to single and double doses, respectively) and 71 HIV-negative controls were enrolled. Among HIV-infected participants, seroconversion increased from 46.7% and 51.7% after the first dose to 77.2% and 83.8% after the second dose of the vaccine using single and double doses, respectively. Participants aged >40 years showed higher seroconversion compared to younger participants. Seroconversion among HIV-infected women and those with nadir CD4<200 cells/mm3 was significantly higher with double doses. Persistence of protective antibodies six months after vaccination was achieved by 80% and 89.9% of the HIV-infected participants who received single and double doses, respectively.Conclusions/SignificanceOur results support the recommendation of two double doses of adjuvanted H1N1pdm09 vaccine for HIV-infected individuals, particularly women, and those aged >40 years or with nadir CD4<200 cells/mm3, to achieve antibody levels that are both higher and more sustained.Trial RegistrationClinicalTrials.gov NCT01155037

Compatibility of ASO3-adjuvanted H1N1pdm09 and seasonal trivalent influenza vaccines in adults: Results of a randomized, controlled trial

When Canada chose a novel adjuvanted vaccine to combat the 2009 influenza pandemic, seasonal trivalent inactivated vaccine (TIV) was also available but compatibility of the two had not been assessed. To compare responses after concurrent or sequential administration of these vaccines, adults 20–59 years old were randomly assigned (1:1) to receive ASO3-adjuvanted H1N1pdm09 vaccine (Arepanrix®, GSK, Quebec City, Quebec), with TIV (Vaxigrip®, Sanofi Pasteur, Toronto) given concurrently or 21 days later. Blood was obtained at baseline and 21 days after each vaccination to measure hemagglutination inhibition (HAI) titers. Adverse effects were assessed using symptom diaries and personal interviews. 282 participants completed the study (concurrent vaccines 145, sequential vaccines 137). HAI titers to H1N1pdm09 were ≥40 at baseline in 15–18% of participants and following vaccination in 91–92%. Initially seropositive subjects (titer ≥10) had lower H1N1pdm09 geometric mean HAI titers (GMT) after concurrent than separate vaccinations (320.0 vs 476.5, p=0.039) but both exceeded GM responses of initially naïve participants, which were unaffected by concurrent TIV. Responses to TIV were not lower after concurrent than separate vaccination. Adverse event rates were not increased by concurrent vaccinations above those with H1N1pdm09 vaccine alone. This adjuvanted H1N1pdm09 vaccine was immunogenic and compatible with concurrently administered TIV.

Increased hemagglutinin content in a reassortant 2009 pandemic H1N1 influenza virus with chimeric neuraminidase containing donor A/Puerto Rico/8/34 virus transmembrane and stalk domains

The glycoproteins, heamagglutinin (HA) and neuraminidase (NA) of influenza virus confer host protective immune responses during vaccination, which is the most effective approach for preventing influenza-associated morbidity and mortality. Since the functional balance between the HA and NA proteins may affect viral receptor binding and replication, a pandemic influenza A virus (H1N1 pdm09), strain A/Texas/05/2009, was optimized to elevate its HA antigen content by modifying the NA gene. In this study, we have constructed two 2:6 reassortant viruses between pdmH1N1 (A/Texas/05/2009) and A/Puerto Rico/8/34 (PR8), in which the NA gene of A/Texas/05/2009 was modified to contain part of the NA gene from PR8. One chimeric NA virus has the PR8 transmembrane (TM) region (HNtm 2:6) and the other contains both the PR8 NA TM and stem regions (HNst 2:6). Using quantitative reverse phase-HPLC (RP-HPLC) analysis, we observed that the HNst2:6 virus contains a higher HA1 content than HN2:6 wild type. In addition, this mutant virus displays a higher HA1 to nucleoprotein (NP) ratio, based on gel electrophoresis densitometry analysis. Furthermore, the neuraminidase activity of purified HNst 2:6 virus is approximately 30% lower than that of HN2:6 virus, which is suggestive of a lower incorporation of NA into the viral envelope. Therefore, we propose that the reduction of NA packaging in the virion may lead to a compensatory increase of HA. Such an improvement in HA yield is possibly beneficial to H1N1 pdm09 vaccine production.

Incidence of H1N1 2009 Virus Infection through the Analysis of Paired Plasma Specimens among Blood Donors, France

BackgroundKnowledge of the age-specific prevalence of seroprotection and incidence of seroconversion infection is necessary to complement clinical surveillance data and statistical models. It provides the basis for estimating the future impact of influenza A (H1N1pdm09) and implementing appropriate prevention and response strategies.MethodsUsing a cross-sectional design, two-stage stratified sampling and paired plasma samples, we estimated the age-specific prevalence of a protective level of H1N1pdm09 antibodies in the French adult population before and after the 2009/10 pandemic, and the proportion of those susceptible that seroconverted due to infection, from a single sample of 1,936 blood donors aged 20–70 years in mainland France in June 2010. Samples with a haemagglutination inhibition (HI) titre ≥1∶40 were considered seropositive, and seroconversion due to infection was defined as a 4-fold increase in titre in the absence of H1N1pdm09 vaccination or pre-pandemic seropositivity.ResultsOut of the 1,936 donors, 1,708 were included in the analysis. Seroprevalence before the pandemic was 6.7% (95% CI 5.0, 8.9) with no significant differences by age-group (p = 0.3). Seroprevalence afterwards was 23.0% (95% CI 17.7, 29.3) with 20–29 year olds having a higher level than older groups (p<0.001). Seroconversion due to infection was 12.2% (95% CI 6.9, 20.5). Younger age-group, vaccination against H1N1 and being seropositive before the pandemic were strongly associated with post-pandemic seropositivity.ConclusionsBefore the 2009/2010 winter influenza season, only 6.7% of the French mainland population aged 20–70 had a level of antibodies usually considered protective. During the first pandemic wave, 12.2% of the population seroconverted due to infection and the seroprevalence after the wave rose to 23%, either due to prepandemic seropositivity, infection or vaccination. This relatively low latter figure contributed to an extension of target groups for influenza vaccination for the 2010/2011 season.

Immune Response Following H1N1pdm09 Vaccination: Differences in Antibody Repertoire and Avidity in Young Adults and Elderly Populations Stratified by Age and Gender

The H1N1 2009 influenza (H1N1pdm09) pandemic had unexpected features, including lower morbidity and mortality in elderly populations. We performed in-depth elucidation of antibody responses generated post-H1N1pdm09 vaccination in elderly (aged 66-83 years) and younger (aged 18-45 or 46-65 years) adults using H1N1pdm09 whole-genome-fragment phage display library and measured antibody isotype and affinity to antigenic domains within hemagglutinin (HA). H1N1pdm09 vaccination induced 10-fold higher antibody levels in elderly compared with younger adults. These antibodies primarily targeted the HA1 globular domain, including neutralizing epitopes in the receptor-binding domain. Antibody epitope repertoire, isotype, and affinity maturation after H1N1pdm09 vaccination evolved independently for HA2, HA1, and HA1 N-terminus antigenic regions. Postvaccination serum samples from elderly subjects demonstrated substantially higher avidity than from younger subjects (>60% vs <30% resistance to 7 mol/L urea) and slower antibody dissociation rates using surface plasmon resonance. We also identified a gender difference in postvaccination antibody avidity (female < male subjects) in adults <65 years old. This is the first study in humans that provides evidence for a qualitatively superior antibody response in elderly adults after H1N1pdm09 vaccination. These findings may help explain the age-related mortality observed during the H1N1pdm09 pandemic. The difference in gender specific avidity merits further exploration.

Recombinant HA1 produced in E. coli forms functional oligomers and generates strain-specific SRID potency antibodies for pandemic influenza vaccines

Vaccine production and initiation of mass vaccination is a key factor in rapid response to new influenza pandemic. During the 2009–2010 H1N1 pandemic, several bottlenecks were identified, including the delayed availability of vaccine potency reagents. Currently, antisera for the single-radial immunodiffusion (SRID) potency assay are generated in sheep immunized repeatedly with HA released and purified after bromelain-treatment of influenza virus grown in eggs. This approach was a major bottleneck for pandemic H1N1 (H1N1pdm09) potency reagent development in 2009. Alternative approaches are needed to make HA immunogens for generation of SRID reagents in the shortest possible time. In this study, we found that properly folded recombinant HA1 globular domain (rHA1) from several type A viruses including H1N1pdm09 and two H5N1 viruses could be produced efficiently using a bacterial expression system and subsequent purification. The rHA1 proteins were shown to form functional oligomers of trimers, similar to virus derived HA, and elicited high titer of neutralizing antibodies in rabbits and sheep. Importantly, the immune sera formed precipitation rings with reference antigens in the SRID assay in a dose-dependent manner. The HA contents in multiple H1N1 vaccine products from different manufacturers (and in several lots) as determined with the rHA1-generated sheep sera were similar to the values obtained with a traditionally generated sheep serum from NIBSC. We conclude that bacterially expressed recombinant HA1 proteins can be produced rapidly and used to generate SRID potency reagents shortly after new influenza strains with pandemic potential are identified.