Pre-vaccination immunity and immune responses to a cell culture-derived whole-virus H1N1 vaccine are similar to a seasonal influenza vaccine

Background

Immune responses to novel pandemic influenza vaccines may be influenced by previous exposure to antigenically similar seasonal strains.

Methods

An open-label, randomized, phase I/II study was conducted to assess the immunogenicity and safety of a non-adjuvanted, inactivated whole-virus H1N1 A/California/07/2009 vaccine. 408 subjects were stratified by age (18–59 and >60 years) and randomized 1:1 to receive two vaccinations with either 3.75 or 7.5 μg hemagglutinin antigen 21 days apart. Safety, immunogenicity and the influence of seasonal influenza vaccination and antibody cross-reactivity with a seasonal H1N1 strain was assessed.

Results

A single vaccination with either dose induced substantial increases in H1N1 A/California/07/2009 hemagglutination inhibition (HI) and neutralizing (MN) antibody titers in both adult and elderly subjects. A single 7.5 μg dose induced seroprotection rates of 86.9% in adults and 75.2% in elderly subjects. Two 7.5 μg vaccinations induced seroprotection rates in adult and elderly subjects of 90.9% and 89.1%, respectively. The robust immune response to vaccination was confirmed by analyses of neutralizing antibody titers. Both HI and MN antibodies persisted for ≥6 months post-vaccination. Between 34% and 49% of subjects had seroprotective levels of H1N1 A/California/07/2009 antibodies at baseline. Higher baseline HI titers were associated with receipt of the 2008–09 or 2009–10 seasonal influenza vaccine. High baseline A/California/07/2009 neutralizing antibody titers were also associated with high baseline titers against A/New Caledonia/20/99, a seasonal H1N1 strain which circulated and was included in the seasonal vaccine from 2000–01 to 2006–07. Pre-adsorption with A/H1N1/New Caledonia/20/99 antigen reduced A/H1N1/California/07/2009 baseline titers in 55% of tested sera. The vaccine was well tolerated with low rates of fever.

Conclusions

A whole-virus H1N1 A/California/07/2009 vaccine was safe and well tolerated and a single dose induced substantial immune responses similar to seasonal influenza vaccines, probably due to immunological priming by previous seasonal influenza vaccines or infections.     

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.     

A cell culture-derived whole-virus H5N1 vaccine induces long-lasting cross-clade protective immunity in mice which is augmented by a homologous or heterologous booster vaccination

Background

Preparation for an H5N1 influenza pandemic in humans could include priming the population in the pre-pandemic period with a vaccine produced from an existing H5N1 vaccine strain, with the possibility of boosting with a pandemic virus vaccine when it becomes available. We investigated the longevity of the immune response after one or two priming immunizations with a whole-virus H5N1 vaccine and the extent to which this can be boosted by later immunization with either a homologous or heterologous vaccine.

Methods

Mice received one or two priming immunizations with a Vero cell culture-derived, whole-virus clade 1 H5N1 vaccine formulated to contain either 750 ng or 30 ng hemagglutinin. Six months after the first priming immunization, mice received either a booster immunization with the same clade 1 vaccine or a heterologous clade 2.1 vaccine, or buffer. Humoral and cellular immune responses were evaluated before and at regular intervals after immunizations. Three weeks after booster immunization, mice were challenged with a lethal dose of wild-type H5N1 virus from clades 1, 2.1 or 2.2 and survival was monitored for 14 days.

Results

One or two priming immunizations with the 750 ng or 30 ng HA formulations, respectively, induced H5N1-neutralizing antibody titers which were maintained for ≥6 months and provided long-term cross-clade protection against wild-type virus challenge. Both humoral and cellular immune responses were substantially increased by a booster immunization after 6 months. The broadest protective immunity was provided by an immunization regimen consisting of one or two priming immunizations with a clade 1 vaccine and a boosting immunization with a clade 2.1 vaccine.

Conclusions

These data support the concept that pre-pandemic vaccination can provide robust and long-lasting H5N1 immunity which could be effectively boosted by immunization either with another pre-pandemic vaccine or with the pandemic strain vaccine.     

Inactivated trivalent seasonal influenza vaccine induces limited cross-reactive neutralizing antibody responses against 2009 pandemic and 1934 PR8 H1N1 strains

Background

In June 2009, we conducted a prospective study in Singapore on 51 individuals to determine their serologic responses before and following receipt of the 2009 Southern Hemisphere seasonal influenza vaccine.

Materials and methods

Paired serum samples were obtained before and 3–4 weeks after vaccination. Virus microneutralization assays were performed to quantify antibodies against A/Brisbane/59/2007 vaccine, pandemic H1N1-2009 and A/Puerto Rico/08/34 H1N1 strains.

Results

Post-vaccination, 43%, 12% and 24% of subjects displayed a 4-fold or greater rise in neutralizing antibody titers against the three strains, respectively. There was a positive correlation among individuals who showed increased titers to both pandemic H1N1-2009 and A/Puerto Rico/08/34 (p < 0.001). However, this correlation was not observed for A/Brisbane/59/2007 with either strain. The relative conservation and accessibility of predicted B-cell epitopes may explain the limited cross-reactivity of the antibodies directed against common H1N1 epitopes.

Conclusions

These results suggest that seasonal influenza vaccination confers a certain degree of cross-protection to other H1N1 strains. The correlation in cross-reactive antibody titers to A/Puerto Rico/08/34 and pandemic H1N1-2009 implies that previous exposure to pre-1957 H1N1 strains may confer some protection against the 2009 pandemic strain.     

A randomised, single-blind, dose-range study to assess the immunogenicity and safety of a cell-culture-derived A/H1N1 influenza vaccine in adult and elderly populations

Background

Modern cell-culture production techniques and the use of adjuvants helps to ensure that the global demand for pandemic influenza vaccine can be met. This study aimed to assess the immunogenicty and safety profiles of various cell-culture-derived A/H1N1 pandemic vaccine formulations in healthy adult and elderly subjects.

Methods

Adult (18–60 years) subjects (n = 544) received vaccine either containing 3.75 μg of antigen with half the standard dose of MF59^® (Novartis Vaccines and Diagnostics) adjuvant, 7.5 μg antigen with a full dose of MF59, or a non-adjuvanted vaccine containing 15 μg of antigen. Elderly (≥61 years) subjects (n = 268) received either the 3.75 μg or 7.5 μg adjuvanted formulations. Two priming vaccine doses were administered 3 weeks apart, followed by a single booster dose of seasonal influenza vaccine 1 year later. Immunogenicity was assessed 3 weeks after each vaccination. The safety profile of each formulation was evaluated throughout the study.

Results

A single primary dose of each A/H1N1 vaccine formulation was sufficient to meet all three European (CHMP) licensure criteria for pandemic influenza vaccines in adult subjects. Two licensure criteria were met after one vaccine dose in elderly subjects; two primary doses were required to meet all three criteria in this age group. The highest antibody titres were observed in response to the 7.5 μg vaccine containing a full dose of MF59 adjuvant. All subjects rapidly generated seroprotective antibody titres in response to booster vaccination.

Conclusion

This study identified one 3.75 μg vaccine dose containing half the standard dose of MF59 adjuvant as optimal for adults, two doses were optimal for elderly subjects. The antigen-sparing properties of MF59, and rapid, modern, cell-culture production techniques represent significant steps towards meeting the global demand for influenza vaccine.     

Factors mediating seasonal and influenza A (H1N1) vaccine acceptance among ethnically diverse populations in the urban south

Objective

We examined the acceptability of the influenza A (H1N1) and seasonal vaccinations immediately following government manufacture approval to gauge potential product uptake in minority communities. We studied correlates of vaccine acceptance including attitudes, beliefs, perceptions, and influenza immunization experiences, and sought to identify communication approaches to increase influenza vaccine coverage in community settings.

Methods

Adults ≥18 years participated in a cross-sectional survey from September through December 2009. Venue-based sampling was used to recruit participants of racial and ethnic minorities.

Results

The sample (N = 503) included mostly lower income (81.9%, n = 412) participants and African Americans (79.3%, n = 399). Respondents expressed greater acceptability of the H1N1 vaccination compared to seasonal flu immunization (t = 2.86, p = 0.005) although H1N1 vaccine acceptability was moderately low (38%, n = 191). Factors associated with acceptance of the H1N1 vaccine included positive attitudes about immunizations [OR = 0.23, CI (0.16, 0.33)], community perceptions of H1N1 [OR = 2.15, CI (1.57, 2.95)], and having had a flu shot in the past 5 years [OR = 2.50, CI (1.52, 4.10). The factors associated with acceptance of the seasonal flu vaccine included positive attitudes about immunization [OR = 0.43, CI (0.32, 0.59)], community perceptions of H1N1 [OR = 1.53, CI (1.16, 2.01)], and having had the flu shot in the past 5 years [OR = 3.53, CI (2.16, 5.78)]. Participants were most likely to be influenced to take a flu shot by physicians [OR = 1.94, CI (1.31, 2.86)]. Persons who obtained influenza vaccinations indicated that Facebook (χ² = 11.7, p = 0.02) and Twitter (χ² = 18.1, p = 0.001) could be useful vaccine communication channels and that churches (χ² = 21.5, p < 0.001) and grocery stores (χ² = 21.5, p < 0.001) would be effective “flu shot stops” in their communities.

Conclusions

In this population, positive vaccine attitudes and community perceptions, along with previous flu vaccination, were associated with H1N1 and seasonal influenza vaccine acceptance. Increased immunization coverage in this community may be achieved through physician communication to dispel vaccine conspiracy beliefs and discussion about vaccine protection via social media and in other community venues.     

Effect of two injections of non-adjuvanted influenza A H1N1pdm2009 vaccine in renal transplant recipients: INSERM C09-32 TRANSFLUVAC trial

Background

Enhancing vaccine immunogenicity in kidney transplant recipients, particularly against influenza, is required since the immunosuppression used to prevent graft rejection limits vaccine immunogenicity. We therefore investigated the immunogenicity and safety of a double dose non-adjuvanted vaccination regimen against influenza H1N1pdm2009 in kidney transplant adult recipients.

Methods

A prospective single-arm study was conducted including 121 renal transplant recipients under triple immunosuppressive regimen. Patients received 2 injections (day 0, day 21) of an inactivated, non-adjuvanted H1N1pdm2009 vaccine. Immunogenicity (hemagglutination-inhibition [HI] antibodies and anti-hemagglutin [HA] specific T cells) was evaluated after one and two injections (day 21, day 42) and at 6 months (day 182).

Results

The seroprotection rate (HI antibody titer ≥ 1/40) was 19% at day 0 (n = 119), 53% at day 21 (n = 118), 60% at day 42 (n = 116) (p = 0.013; day 42 vs. day 21) and 56% at day 182 (n = 113). The seroconversion rate was 24% and 32%, the geometric mean fold rise was 3.7 and 4.6 after the first and second injections, respectively. T-cell immunity to the H1N1pdm2009 vaccine showed a two-fold increase from baseline, though not statistically significant, in H1N1pdm2009-HA-specific CD4+ and CD8+ T cells in 34% and 48% of cases, respectively. No rejection episodes related to vaccination were observed while the donor-specific antibodies and creatinine clearance remained unchanged throughout the study.

Conclusion

Administration of two doses of the non-adjuvanted influenza H1N1pdm2009 vaccine in renal transplant patients is safe and induces a significant seroprotection, not strong enough yet to meet European or US requirements for adults below 60 years, but comparable to seroprotection levels usually observed in the non immunosuppressed elderly population or conferred by a single dose of adjuvanted vaccine in solid organ transplant recipients. These results provide useful indications for future strategies required to improve immunogenicity of vaccines against influenza in transplanted patients.     

Randomized clinical trial of immunogenicity and safety of a recombinant H1N1/2009 pandemic influenza vaccine containing Advax™ polysaccharide adjuvant

Background

Timely vaccine supply is critical during influenza pandemics. A recombinant hemagglutinin (rHA)-based vaccine could overcome production hurdles of egg-based vaccines but has never previously been tested in a real-life pandemic setting. The primary aim was to determine the efficacy of a recombinant pandemic vaccine and whether its immunogenicity could be enhanced by a novel polysaccharide adjuvant (Advax™).

Methods

281 adults aged 18–70 years were recruited in a randomized, subject and observer blinded, parallel-group study of rHA H1N1/2009 vaccine with or without adjuvant. Immunizations were at 0 and 3 weeks with rHA 3, 11 or 45 μg. Serology and safety was followed for 6 months.

Results

At baseline, only 9.1% of subjects (95% CI: 6.0–13.2) had seroprotective H1N1/2009 titers. Seroconversion rates varied by rHA dose, presence of adjuvant, subject age and number of immunizations. Eighty percent (95% CI: 52–96) of 18–49 year olds who received rHA 45 μg with adjuvant were seroprotected at week 3, representing a 11.1-fold increase in antibody titers from baseline. Advax™ adjuvant increased seroprotection rates by 1.9 times after the first, and 2.5 times after the second, immunization when compared to rHA alone. Seroprotection was sustained at 26 weeks and the vaccine was well tolerated with no safety issues.

Conclusions

The study confirmed the ability to design, manufacture, and release a recombinant vaccine within a short time from the start of an actual influenza pandemic. Advax™ adjuvant significantly enhanced rHA immunogenicity.     

Antibody persistence and response to 2010-2011 trivalent influenza vaccine one year after a single dose of 2009 AS03-adjuvanted pandemic H1N1 vaccine in children

Background

In 2009, several countries used the ASO3-adjuvanted pandemic A/H1N1 vaccine. We assessed the persistence of antibody and the priming induced by a single paediatric dose of this vaccine in children.

Methods

Children aged 15-120 months vaccinated one year before with the ASO3-adjuvanted monovalent pandemic vaccine were tested for the presence of antibody against 2010-2011 TIV components (A/California/7/2009(H1N1), A/Wisconsin/15/2009 (H3N2 A/Perth/16/2009-like) and B/Brisbane/60/2008) before and 21-28 days after each dose of 2010-2011 TIV. Hemagglutination-inhibition (HAI) assay was used. Children received one or two doses of 2010-2011 TIV at 21-28 days interval in relation with their previous immunization status.

Results

The results of 128 children were included in the ATP analysis. Before the 2010-2011 TIV administration, 46% of children showed sero-protection to the A/California/7/2009(H1N1) strain (HAI titre ≥40) with lower rates of sero-protection to the H3N2A/Perth/16/2009 (37%) and B/Brisbane/60/2008 (19%). After the first dose of 2010-2011 TIV, 98%, 75%, and 57% of vaccinees attained a sero-protective titre to A/California/7/2009(H1N1), A/Perth/16/2009(H3N2), and B/Brisbane/60/2008 strain, respectively. The youngest age group showed significantly lower antibody response to the influenza B component compared to the older age groups after the first dose of vaccine. Among vaccinees who received the second dose of TIV, 96% and 87% had a sero-protective titre to H3N2A/Perth/16/2009 and B/Brisbane/60/2008, respectively. The 2010-2011 TIV was well tolerated.

Conclusions

We found substantial persistence of antibody to the A/California/7/2009 strain one year after a single paediatric dose of AS03-adjuvanted pandemic vaccine and a seroprotective level of antibody to this strain in virtually all children who received one year later a single dose of the 2010-2011 TIV. In contrast, two doses of the 2010-2011 TIV were necessary to induce an adequate immune response to the A/Perth/16/2009(H3N2) and B/Brisbane/60/2008 strains in children previously naïve to seasonal vaccine.     

Cell culture (Vero cell) derived whole-virus non-adjuvanted H5N1 influenza vaccine induces long-lasting cross-reactive memory immune response: Homologous or heterologous booster response following two dose or single dose priming

Background

Influenza pandemic preparedness involves priming of the population with pre-pandemic vaccines. Such vaccines should be well tolerated and induce a long-lasting immunological memory that can effectively be boosted with a single dose of pandemic vaccine once available. The presented studies assessed different prime-boost regimens with a Vero cell-derived whole virus non-adjuvanted H5N1 vaccine.

Methods

In one study, 281 healthy adult (18–59 years) and 280 elderly (≥60 years) subjects received two vaccinations, 21 days apart, with Vero cell-derived whole virus non-adjuvanted H5N1 vaccine (7.5 μg HA antigen A/Vietnam/1203/2004) followed by a 6, 12–15, or 24 month booster (7.5 or 3.75 μg A/Indonesia/05/2005 or A/Vietnam/1203/2004). In the other study, 230 healthy adults (18–59 years) received single dose priming (7.5 μg A/Vietnam/1203/2004) followed by a 12 month booster (7.5 or 3.75 μg A/Indonesia/05/2005). Antibody responses were assessed by microneutralization (MN) and single radial hemolysis (SRH) assay. Vaccine safety was assessed throughout.

Results

Two dose priming was equally immunogenic in adults and the elderly: >72% of subjects in each population achieved MN titers ≥1:20 after the second vaccination. Booster vaccinations at 6, 12–15, and 24 months induced substantial antibody increases to both strains: after a 7.5 μg A/Indonesia/05/2005 booster, 93–95% of adults and 72–84% of the elderly achieved MN titers ≥ 1:20 against this strain. Homologous and heterologous booster responses were higher in the 7.5 μg dose group than in the 3.75 μg dose group. Booster responses following single dose priming were similar; a 7.5 μg booster dose induced homologous MN titers ≥1:20 in 93% of subjects.

Conclusions

A Vero cell derived whole virus non-adjuvanted H5N1 influenza vaccine is well tolerated and induces long-lasting cross-clade immunological memory that can be effectively boosted 1–2 years after two dose or single dose priming, supporting its suitability for pre-pandemic vaccination.     

Association between obesity and vulnerability and serologic response to influenza vaccination in older adults

Background

Serologic response to influenza vaccination declines with age. Few other host factors are known to be associated with serologic response. Our objective was to determine whether obesity and vulnerability independently predicted serologic response to influenza vaccination.

Methods

Adults ≥50 years were recruited during the 2008–2009 influenza season. Subjects provided pre- and post-vaccination sera for measuring antibody titers to 2008–2009 vaccine components. Body mass index (BMI) was calculated as weight (kg)/height (m²). Data were collected on vulnerability using the vulnerable elders survey (VES13). Logistic regression evaluated the associations between obesity and vulnerability and the serologic response to vaccination (both seroprotection and seroconversion), adjusting for gender, age, comorbidities, pre-vaccination titer, and site.

Results

Mean (±standard deviation) age of 415 study subjects was 65 ± 10 years; 40% were obese. Mean BMI was 29 ± 5.6 kg/m²; mean VES13 was 1.6 ± 1.8. The proportions of subjects who seroconverted and had seroprotective titers were 40% and 49%, respectively, for A/Brisbane/59 (H1N1); 73% and 80% for A/Brisbane/10 (H3N2); and 34% and 94% for B/Florida. Modified VES-13 (score 0–10, with 10 being most vulnerable) was not associated with seroprotection against H1N1 or H3N2, and VES-13 was directly associated with seroconversion to H1N1 but not H3N2 or B. Obesity (BMI ≥ 30 kg/m² vs. BMI 18.5–30 kg/m²) was not associated with seroprotection for H1N1 or H3N2; obesity was directly associated with seroconversion to H3N2 but not H1N1 or B. Age was inversely associated with seroprotection and seroconversion against H1N1 and with seroconversion to influenza B.

Conclusion

Based on this sample of older healthy subjects, there were no consistent relationships between VES 13 or obesity and either seroprotection or seroconversion to three influenza vaccine antigens.     

Development of VAX128, a recombinant hemagglutinin (HA) influenza-flagellin fusion vaccine with improved safety and immune response

Background

We evaluated the safety and immunogenicity profiles of 3 novel influenza vaccine constructs consisting of the globular head of the HA1 domain of the Novel H1N1 genetically fused to the TLR5 ligand, flagellin. HA1 was fused to the C-terminus of flagellin in VAX128A, replaced the D3 domain of flagellin in VAX128B and was fused in both positions in VAX128C.

Methods

In a dose escalation trial, 112 healthy subjects 18–49 and 100 adults ≥65 years old were enrolled in a double blind, placebo controlled clinical trial at two centers. Vaccines were administered IM at doses ranging from 0.5 to 20 μg. VAX128C was selected for second study performed in 100 subjects 18–64 years old comparing 1.25 and 2.5 μg doses. All subjects were followed for safety and sera collected pre- and post-vaccination were tested by hemagglutination-inhibition (HAI). Serum C-reactive protein and cytokine levels were also measured.

Conclusions

In the first study high HAI titers and high seroconversion and seroprotection rates were observed at doses ≥2.5 μg in adults 18–49. In adults ≥65 years, the vaccines doses of ≥4 μg were required to induce a ≥4-fold rise in HAI titer, 50% seroconversion and 70% seroprotection. Based on safety, VAX128A was tested up to 8 μg, VAX128B to 16 μg and VAX128C to 20 μg. Dose escalation for VAX128A was stopped at 8 μg because one subject had temperature 101.6 °F associated with a high CRP response, VAX128B was stopped at 16 μg because of a severe AE associated with a high CRP and IL-6 response. VAX128C was not stopped before reaching the 20 μg dose. In the second study VAX128C was well tolerated among 100 subjects who received 1.25 or 2.5 μg. The peak GMT was 385 (95%CI 272–546), 79% (71–87%) seroconversion and 92% (84–96%) seroprotection.

Discussion

Flagellin adjuvanted vaccines can be designed to minimize reactogenicity and retain immunogenicity, thereby representing a promising next generation vaccine technology.     

The impact of pandemic A(H1N1)pdm09 influenza and vaccine-associated adverse events on parental attitudes and influenza vaccine uptake in young children

Introduction

Parental attitudes towards vaccination significantly influence vaccine uptake. The A(H1N1)pdm09 influenza pandemic was followed in 2010 by an unprecedented increase in febrile reactions in children receiving trivalent inactivated influenza vaccine manufactured by bioCSL. Uptake of TIV in children <5 years in Western Australia (WA) decreased in 2010 and has remained low. The impact of pandemic A(H1N1)pdm09 and adverse-events on parental attitudes towards vaccination is uncertain.

Materials and Methods

A parental attitudes survey towards influenza illness and vaccination was conducted as part of the West Australian Influenza Vaccine Effectiveness study. Vaccination status was assessed by parental interview and confirmed by the national register and/or vaccine providers. Parental attitudes from vaccinated and unvaccinated children and attitudes in 2008–2009 and 2010–2012 were compared. Principal Component Analysis was conducted to determine core attitudes that influenced vaccine uptake.

Results

Vaccination history and parental attitude surveys were available from 2576 children. Parents of fully vaccinated children less frequently stated that influenza was a mild disease, more frequently stated that influenza vaccine was safe and were less frequently worried about vaccine side effects.Uptake of influenza vaccine decreased significantly from 2010 onwards. From 2010, parents were less concerned about severe influenza, but more concerned about vaccine side effects and safety. Despite this significant shift in attitudes towards influenza vaccine, parental acceptance of vaccines on the national immunisation program did not change. Principal Component Analysis revealed that attitudes around vaccine safety and efficacy were the most important attitudes impacting on vaccine uptake.

Conclusions

Parental attitudes to influenza vaccine changed from 2010. Confidence in the WA preschool influenza vaccination program remains low yet appeared unchanged for other vaccines. Restoring public confidence in childhood influenza vaccination is needed before uptake can be improved.     

A non-adjuvanted whole-virus H1N1 pandemic vaccine is well tolerated and highly immunogenic in children and adolescents and induces substantial immunological memory

This phase 1/2 open-label, randomized clinical study investigated the safety and immunogenicity of a non-adjuvanted, whole virus, Vero cell-derived H1N1 pandemic influenza vaccine (A/H1N1/California/07/2009) in children and adolescents (6 months to 17 years). Subjects were stratified by age (6–11 months, 12–35 months, 3–8 years, 9–17 years) to receive two vaccinations 21 days apart of either the 3.75 μg or 7.5 μg dose. A booster with a licensed trivalent seasonal (2010/2011) influenza vaccine was administered one year after the first vaccination to a subgroup that had previously received the 7.5 μg dose.     

Influenza pandemic (H1N1) 2009 activity during summer 2009. Effectiveness of the 2008-9 trivalent vaccine against pandemic influenza in Spain

Introduction

The Spanish influenza surveillance system (SISS) maintained its activity during the summer of 2009 to monitor the influenza pandemic.

Objectives

To describe pandemic influenza activity from May to September 2009 and to estimate the effectiveness of the 2008-9 seasonal influenza vaccine against laboratory-confirmed pandemic (H1N1) 2009 influenza.

Methods

Data from the SISS were used to identify the trend of pandemic (H1N1) 2009 influenza outside the influenza season. For the effectiveness study, we compared the vaccination status of notified cases [influenza-like illnesses (ILI) laboratory confirmed as pandemic influenza] with that of the test-negative controls.

Results

The first laboratory-confirmed case of the pandemic virus was notified in the system in week 20/2009. The ILI rate increased gradually in the study period, exceeding basic activity in week 38. The proportion of pandemic (H1N1) 2009 influenza viruses detected by the system represented 14% in week 20/2009 and rapidly increased to 90% in week 34. The adjusted vaccine effectiveness of the 2008-9 seasonal vaccine against laboratory-confirmed pandemic influenza was 12% (-30; 41).

Conclusions

The SISS became an essential tool for pandemic monitoring in Spain. The improved SISS will provide more accurate information on influenza activity in future seasonal or pandemic waves. Using surveillance data, we could not demonstrate the effectiveness of the seasonal 2008-9 vaccine against laboratory-confirmed pandemic influenza.     

Live attenuated H7N7 influenza vaccine primes for a vigorous antibody response to inactivated H7N7 influenza vaccine

Background

H7 influenza viruses have emerged as potential pandemic threat. We evaluated the safety and immunogenicity of two candidate H7 pandemic live attenuated influenza vaccines (pLAIV) and their ability to prime for responses to an unadjuvanted H7 pandemic inactivated influenza vaccine (pIIV).

Methods

Healthy seronegative adults received two doses of A/Netherlands/219/03 (H7N7) or one dose of A/chicken/British Columbia/CN-6/04 (H7N3) pLAIV all given as 10^7.5 50% tissue culture infective doses (TCID₅₀) intranasally. A subset of subjects received one 45 μg dose of H7N7 pIIV containing the A/Mallard/Netherlands/12/2000 HA intramuscularly 18–24 months after pLAIV. Viral shedding was assessed by culture and real-time polymerase chain reaction (rRT-PCR), B cell responses following pLAIV were evaluated by ELISPOT and flow cytometry. Serum antibody was assessed by hemagglutination-inhibition (HAI), microneutralization (MN) and ELISA assays after each vaccine.

Results

Serum HAI or MN responses were not detected in any subject following one or two doses of either H7 pLAIV, although some subjects had detectable H7 specific B cells after vaccination. However, 10/13 subjects primed with two doses of H7N7 pLAIV responded to a subsequent dose of the homologous H7N7 pIIV with high titer HAI and MN antibody that cross-reacted with both North American and Eurasian lineage H7 viruses, including H7N9. In contrast, naïve subjects and recipients of a single dose of the mismatched H7N3 pLAIV did not develop HAI or MN antibody after pIIV.

Conclusions

While pLAIVs did not elicit detectable serum MN or HAI antibody, strain-specific pLAIV priming established long term immune memory that was cross-reactive with other H7 influenza strains. Understanding the mechanisms underlying priming by pLAIV may aid in pandemic vaccine development.     

Comparison of the safety and immunogenicity of an MF59-adjuvanted with a non-adjuvanted seasonal influenza vaccine in elderly subjects

Aim

Adjuvanted influenza vaccines can overcome the poor antibody response of conventional non-adjuvanted vaccines in the elderly. We evaluated the immunogenicity, safety and clinical effectiveness of an MF59^®-adjuvanted trivalent influenza vaccine (aTIV) compared with a non-adjuvanted vaccine (TIV) in subjects ≥65 years old, with or without co-morbidities.

Methods

In 2010–2011, subjects (N = 7082) were randomized to receive one dose of aTIV or TIV. Co-primary objectives were to assess lot-to-lot consistency of aTIV, non-inferiority, superiority and immunogenicity 22 days after vaccination. Clinical effectiveness, reactogenicity and serious adverse events were monitored up to Day 366.

Results

The immunological equivalence of three lots of aTIV was demonstrated. aTIV was not only non-inferior to TIV but also elicited significantly higher antibody responses at Day 22 than TIV against all homologous and heterologous strains, even in subjects with co-morbidities. Superiority was not established. Reactogenicity was higher in the aTIV group, but reactions were mild to moderate and transient.

Conclusions

aTIV elicited a significantly higher antibody response than TIV, especially against A/H3N2 strains, although superiority by pre-defined criteria was not formally met. The study demonstrates potential immunological benefits of MF59-adjuvanted influenza vaccines for the elderly.This trial was registered with www.clinicaltrials.gov (NCT01162122).     

Responses after one dose of a monovalent influenza A (H1N1) 2009 inactivated vaccine in Chinese population—A practical observation

Background

The globally large-scale immunization was the most important method of controlling the 2009 pandemic influenza.

Methods

We conducted an observational clinical trial, including 148 adults aged 18-60 years to evaluate the safety and immunogenicity of a licensed 2009 H1N1 influenza vaccine. All subjects received a single 15-μg dose of a monovalent, unadjuvanted inactivated vaccine. Antibody titers were measured by means of hemagglutinin-inhibition assays and neutralization assays based on Real-Time Cell Analyzer (RTCA) instruments at baseline, 7 days and 21 days after vaccination.

Results

Local and systemic reactions were respectively reported by 19.1% and 22.1% of subjects. All adverse events were mild to moderate in intensity, without any deaths or serious events. By day 21 after vaccination, hemagglutinin-inhibition antibody titers of 1:40 or more were achieved in 101 of 123 (82.1%) subjects and the geometric mean titers (GMTs) increased to 1:95.27. For neutralization assays, all subjects could provide the protection against wide influenza virus, with the GMT of 1:525.44. Moreover, the rates of seroconversion, as measured using hemagglutinin-inhibition assays and neutralization assays, were 73.98% and 91.87% of subjects, respectively.

Conclusions

A single 15-μg dose of a monovalent, unadjuvanted inactivated 2009 H1N1 influenza vaccine was well tolerated, and induced a protective immune response in the majority of subjects aged 18-60 years (clinical trials gov number, NCT01055990).