Population susceptibility to North American and Eurasian swine influenza viruses in England, at three time points between 2004 and 2011

Age-stratified sera collected in 2004, 2008 and 2010 in England were evaluated for antibody to swine influenza A(H3N2) and A(H1N1) viruses from the United States or Europe as a measure of population susceptibility to the emergence of novel viruses. Children under 11 years of age had little or no measurable antibody to recent swine H3N2 viruses despite their high levels of antibody to recent H3N2 seasonal human strains. Adolescents and young adults (born 1968–1999) had higher antibody levels to swine H3N2 viruses. Antibody levels to swine H3N2 influenza show little correlation with exposure to recent seasonal H3N2 (A/Perth/16/2009) strains, but with antibody to older H3N2 strains represented by A/Wuhan/359/1995. Children had the highest seropositivity to influenza A(H1N1)pdm09 virus, and young adults had the lowest antibody levels to A/Perth/16/2009. No age group showed substantial antibody levels to A/Aragon/RR3218/2008, a European swine H1N1 virus belonging to the Eurasian lineage. After vaccination with contemporary trivalent vaccine we observed evidence of boosted reactivity to swine H3N2 viruses in children and adults, while only a limited boosting effect on antibody levels to A/Aragon/RR3218/2008 was observed in both groups. Overall, our results suggest that different vaccination strategies may be necessary according to age if swine viruses emerge as a significant pandemic threat.

Efficient boosting of the antiviral T cell response in B cell-depleted patients with autoimmune rheumatic diseases following influenza vaccination

OBJECTIVES

Booster vaccination against 2009 H1N1 influenza virus was recommended for rheumatologic patients under immunosuppressive therapy during the 2009/2010 H1N1 pandemic. In this study we assessed whether B cell depletion with rituximab influences of the antiviral immune response in 2009 H1N1 influenza virus-vaccinated patients.

METHODS

Influenza virus-specific immune responses were analysed after the first and a booster vaccination with pandemrixTM in sixteen consecutive rituximab-treated patients with different rheumatic autoimmune disorders. Antibody titers were determined by a haemagglutination-inhibition assay and virus-specific T cell responses were evaluated by a flow cytometry-based intracellular cytokine-secretion assay. Patients showing clinical symptoms of influenza infection were excluded from this study.

RESULTS

Two out of seven patients with low (<10%) and four out of nine with normal (>10%) B cells developed significant antibody responses after the first vaccination. Booster vaccination led to an antibody response in one additional patient. After the first vaccination, virus-specific CD4+ and CD8+ T cell responses were significantly lower in patients with low B cells than in those with normal B cells. Of importance, the booster vaccination stimulated the antiviral T cell response only in patients with low B cells.

CONCLUSIONS

In the absence of a significant effect of booster vaccinations against 2009 H1N1 influenza virus on the humoral immune response in B cell-depleted patients with autoimmune rheumatic diseases, enhanced antiviral T cell responses in patients with low B cells indicate that T cells, maybe, compensate for the impaired humoral immunity in these patients.

Seroprevalence of influenza A(H1N1)pdm09 virus antibody, England, 2010 and 2011

The intense influenza activity in England during the 2010-11 winter resulted from a combination of factors. Population-based seroepidemiology confirms that the third wave of influenza A(H1N1)pdm09 virus circulation was associated with a shift in age groups affected, with the highest rate of infection in young adults.

Randomized controlled trial of high-dose intradermal versus standard-dose intramuscular influenza vaccine in organ transplant recipients

The immunogenicity of standard intramuscular (IM) influenza vaccine is suboptimal in transplant recipients. Also, recent studies suggest that alloantibody may be upregulated due to vaccination. We evaluated a novel high-dose intradermal (ID) vaccine strategy. In conjunction, we assessed alloimmunity. Transplant recipients were randomized to receive IM or high-dose ID vaccine. Strain-specific serology and HLA alloantibody production was determined pre- and postimmunization. In 212 evaluable patients (105 IM, 107 ID), seroprotection to H1N1, H3N2 and B strains was 70.5%, 63.8% and 52.4% in the IM group, and 71.0%, 70.1%, 63.6% in the ID group (p=ns). Seroconversion to ≥1 antigen was 46.7% and 51.4% in the IM and ID groups respectively (p=0.49). Response was more likely in those≥6 months posttransplant (53.2% vs. 19.2%; p=0.001). Use of mycophenolate mofetil was inversely associated with vaccine response in a dose-dependent manner (p<0.001). Certain organ subgroups had higher response rates for influenza B in the ID vaccine group. Differences in anti-HLA antibody production were detected in only 3/212(1.4%) patients with no clinical consequences. High-dose intradermal vaccine is an alternative to standard vaccine and has potential enhanced immunogenicity in certain subgroups. In this large cohort, we also show that seasonal influenza does not result in significant alloantibody production.

Humoral Immune Response following Seasonal Influenza Vaccine in Islet Transplant Recipients

Annual influenza vaccine is recommended for organ transplant recipients, but immunogenicity is known to be suboptimal. Islet transplant recipients receive immunosuppressive therapy, but there are no data on the immunogenicity of influenza vaccine in this population. In this prospective cohort study, adult islet transplant recipients at least 3 months posttransplant were enrolled. All patients received the 2010–2011 seasonal influenza vaccine. Serum was obtained pre- and postvaccination to determine humoral response to each of the three influenza strains included in the vaccine. Adverse effects of vaccine were also noted. A total of 61 islet transplant recipients were enrolled and completed the study protocol. The median time from last transplant was 1.9 years (range 0.26–11.4 years), and most patients had undergone multiple prior islet transplant procedures (90.2%). Overall immunogenicity of the vaccine was poor. Seroconversion rates to H1N1, H3N2, and B antigens were 34.4%, 29.5%, and 9.8%, respectively. In the subset not seroprotected at baseline, a protective antibody titer postvaccination was achieved in 58.6%, 41.9%, and 34.5% of patients, respectively. Patients within the first year of transplant were significantly less likely to seroconvert to at least one antigen (23.5% vs. 54.5%; p = 0.029). Alemtuzumab recipients trended toward lower seroconversion rates (25% vs. 51%; p = 0.11). No vaccine-related safety concerns were identified. Seasonal influenza vaccine had suboptimal immunogenicity in islet transplant recipients especially those who were less than 1 year posttransplant or had received alemtuzumab induction. Novel strategies for protection in this group of patients need further study.

Influenza serological studies to inform public health action: best practices to optimise timing, quality and reporting

BACKGROUND

Serological studies can detect infection with a novel influenza virus in the absence of symptoms or positive virology, providing useful information on infection that goes beyond the estimates from epidemiological, clinical and virological data. During the 2009 A(H1N1) pandemic, an impressive number of detailed serological studies were performed, yet the majority of serological data were available only after the first wave of infection. This limited the ability to estimate the transmissibility and severity of this novel infection, and the variability in methodology and reporting limited the ability to compare and combine the serological data.

OBJECTIVES

  To identify best practices for conduct and standardisation of serological studies on outbreak and pandemic influenza to inform public policy.

METHODS/SETTING

An international meeting was held in February 2011 in Ottawa, Canada, to foster the consensus for greater standardisation of influenza serological studies.

RESULTS

Best practices for serological investigations of influenza epidemiology include the following: classification of studies as pre-pandemic, outbreak, pandemic or inter-pandemic with a clearly identified objective; use of international serum standards for laboratory assays; cohort and cross-sectional study designs with common standards for data collection; use of serum banks to improve sampling capacity; and potential for linkage of serological, clinical and epidemiological data. Advance planning for outbreak studies would enable a rapid and coordinated response; inclusion of serological studies in pandemic plans should be considered.

CONCLUSIONS

Optimising the quality, comparability and combinability of influenza serological studies will provide important data upon emergence of a novel or variant influenza virus to inform public health action.

Comparing the immunogenicity of AS03-adjuvanted 2009 pandemic H1N1 vaccine with clinical protection in priority risk groups in England

In England, during pandemic 2009 H1N1, vaccine efficacy and immunogenicity population studies in priority groups were rolled out in parallel to evaluate the pandemic vaccination programme. This provided a unique opportunity to compare immunogenicity and clinical protection in the same population and thus provide insights into the correlates of protection for the pandemic H1N1 2009 vaccine in risk groups. While clinical protection from AS03-adjuvanted pandemic 2009 H1N1 vaccine was high in those aged <25 years and pregnant women, effectiveness in older adults with chronic conditions has been found to be surprisingly poor. Here we present results from the immunogenicity study derived from the same population. Individuals from priority groups eligible for pandemic vaccination attending participating general practices were recruited. Pre and post-vaccination blood samples were collected and HI antibody testing to assess immune response to vaccination performed. The final cohort consisted of 610 individuals: 60 healthy children aged <5 years; 32 healthy pregnant women; 518 individuals from risk groups. Seroconversion rate in healthy children aged <5 years (87%, 95% CI: 75% to 94%) was higher than that of risk groups combined (65%, 95% CI: 61% to 69%) (p<0.001). Multivariable analysis of risk groups showed that the size of response in those who did seroconvert was lower in those who received the 2009/10 seasonal TIV (Fold effect: 0.52, 0.35 to 0.78). Predicted immunological boosting from higher pre-vaccine titres after 2009 pandemic H1N1 vaccination only occurred in children (seroconversion rate = 92%) and not in individuals aged 10 to 39 from risk groups (seroconversion rate = 74%). The lack of clinical protection identified in the same population in older adults from risk groups could be attributed to these lower seroresponses. Current immunogenicity licensing criteria for pandemic influenza vaccine may not correlate with clinical protection in individuals with chronic disease or immunocompromised.

Severe respiratory illness caused by a novel coronavirus, in a patient transferred to the United Kingdom from the Middle East, September 2012

Coronaviruses have the potential to cause severe transmissible human disease, as demonstrated by the severe acute respiratory syndrome (SARS) outbreak of 2003. We describe here the clinical and virological features of a novel coronavirus infection causing severe respiratory illness in a patient transferred to London, United Kingdom, from the Gulf region of the Middle East.

Severe respiratory illness caused by a novel coronavirus, in a patient transferred to the United Kingdom from the Middle East, September 2012

Coronaviruses have the potential to cause severe transmissible human disease, as demonstrated by the severe acute respiratory syndrome (SARS) outbreak of 2003. We describe here the clinical and virological features of a novel coronavirus infection causing severe respiratory illness in a patient transferred to London, United Kingdom, from the Gulf region of the Middle East.

Strategies for screening blood donors to source convalescent H1N1v plasma for intervention therapy

BACKGROUND AND OBJECTIVES

During the 1918, pandemic blood components were successfully used to treat severe influenza pneumonia. A Proof of Principle trial investigating the clinical benefit of convalescent plasma was proposed in the 2009 H1N1v epidemic with the aim of screening donors for high titre antibody in order to stockpile plasma packs to be used for treatment for severe pneumonia.

MATERIALS AND METHODS

Serum samples were collected from donors. IgG antibody capture format enzyme-linked immunoassays using recombinant proteins (GACELISAs) were compared with microneutralization (MN) and haemagglutination inhibition (HAI). The influence of age and history of influenza-like illness (ILI) on the detection of high titre antibody was examined.

RESULTS

1598 unselected donor sera collected in October and December 2009 were tested by HAI. The HAI and demographic data defined a possible strategy for selective donor screening. One of the GACELISAs was highly specific for recent infection but showed lower sensitivity than HAI.

CONCLUSIONS

During the 2009 pandemic screening 17- to 30-year-old donors by HAI delivered around 10% with high antibody levels. The ELISA using a short recombinant H1N1v HA detected fewer reactives but was more specific for high titre antibody (≥1:256). Screening strategies are proposed based on using HAI on serum or GACELISA on plasma.

Seroepidemiologic study of pandemic (H1N1) 2009 during outbreak in boarding school, England

TOC Summary: Prophylactic antiviral agents lower the odds of acute respiratory infection but not serologic infection.

Keywords: pandemic, influenza, A/H1N1, pandemic (H1N1) 2009, seroepidemiology, outbreak, serology, asymptomatic, prophylaxis, antiviral agents, vaccine, viruses, research

We conducted a seroepidemiologic study during an outbreak of pandemic (H1N1) 2009 in a boarding school in England. Overall, 353 (17%) of students and staff completed a questionnaire and provided a serum sample. The attack rate was 40.5% and 34.1% for self-reported acute respiratory infection (ARI). Staff were less likely to be seropositive than students 13–15 years of age (staff 20–49 years, adjusted odds ratio [AOR] 0.30; >50 years AOR 0.20). Teachers were more likely to be seropositive than other staff (AOR 7.47, 95% confidence interval [CI] 2.31–24.2). Of seropositive persons, 44.6% (95% CI 36.2%–53.3%) did not report ARI. Conversely, of 141 with ARI and 63 with influenza-like illness, 45.8% (95% CI 37.0%–54.0%) and 30.2% (95% CI 19.2%–43.0%) had negative test results, respectively. A weak association was found between seropositivity and a prophylactic dose of antiviral agents (AOR 0.55, 95% CI 0.30–0.99); prophylactic antiviral agents lowered the odds of ARI by 50%.

H1N1 antibody persistence 1 year after immunization with an adjuvanted or whole-virion pandemic vaccine and immunogenicity and reactogenicity of subsequent seasonal influenza vaccine: a multicenter follow-on study

Two doses of AS03_B-adjuvanted pandemic influenza vaccine may be sufficient to maintain seroprotection across 2 influenza seasons. Administration of trivalent influenza vaccine to children who previously received 2 doses of pandemic influenza vaccine is safe and is immunogenic for the H1N1 strain.

Background. We investigated antibody persistence in children 1 year after 2 doses of either an AS03_B-adjuvanted split-virion or nonadjuvanted whole-virion monovalent pandemic influenza vaccine and assessed the immunogenicity and reactogenicity of a subsequent dose of trivalent influenza vaccine (TIV).

Methods. Children previously immunized at age 6 months to 12 years in the original study were invited to participate. After a blood sample was obtained to assess persistence of antibody against swine influenza A/H1N1(2009) pandemic influenza, children received 1 dose of 2010/2011 TIV, reactogenicity data were collected for 7 days, and another blood sample was obtained 21 days after vaccination.

Results. Of 323 children recruited, 302 received TIV. Antibody persistence (defined as microneutralization [MN] titer ≥1:40) 1 year after initial vaccination was significantly higher in the AS03_B-adjuvanted compared with the whole-virion vaccine group, 100% (95% confidence interval [CI], 94.1%–100%) vs 32.4% (95% CI, 21.5%–44.8%) in children immunized <3 years old and 96.9% (95% CI, 91.3%–99.4%) vs 65.9% (95% CI, 55.3%–75.5%) in those 3–12 years old at immunization, respectively (P < .001 for both groups). All children receiving TIV had post-vaccination MN titers ≥1:40. Although TIV was well tolerated in all groups, reactogenicity in children <5 years old was slightly greater in those who originally received AS03_B-adjuvanted vaccine.

Conclusions. This study provides serological evidence that 2 doses of AS03_B-adjuvanted pandemic influenza vaccine may be sufficient to maintain protection across 2 influenza seasons. Administration of TIV to children who previously received 2 doses of either pandemic influenza vaccine is safe and is immunogenic for the H1N1 strain.

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.

Monoclonal antibodies to the haemagglutinin HA1 subunit of the pandemic influenza A/H1N1 2009 virus and potential application to serodiagnosis

In order to provide specific serological reagents for pandemic influenza A/H1N1 2009 virus, monoclonal antibodies (Mabs) to recombinant haemagglutinin component HA1 (rHA1) were generated after fusing spleen cells from a mouse immunized with rHA1 protein derived from influenza strain A/California/06/09 H1N1 with a mouse myeloma cell line. Five hybridoma clones secreting Mabs specific for the rHA1 protein derived from pandemic influenza A/H1N1 2009 and not for rHA1 from seasonal H1N1 influenza strains A/Brisbane/59/07 and A/Solomon Islands/03/06 were identified by EIA. Mabs 7H4, 9A4, and 9E12 were reactive in Western blots with full length rHA and/or rHA1 subunit derived from A/California/06/09 strain. Only Mab 1F5 inhibited haemagglutination of turkey red blood cells with recombinant NIBRG-121 virus derived from A/California/07/09, but did not react in Western blots. Immunostaining of MDCK cells infected with NIBRG-121 was localized to the membrane/cytoplasm for four of the reactive Mabs. The differing reactivity of the Mabs in Western blots, immunostaining, EIA, and haemagglutination inhibition assay suggest that at least four of the five Mabs recognize different epitopes on HA1 of the pandemic influenza A/H1N1 2009 virus. Ferret antisera to pandemic influenza A/H1N1 2009 (A/England/195/09 and A/California/07/09 strains) and sera from human subjects vaccinated with Influenza A (H1N1) 2009 Monovalent Vaccine (CELTURA®, Novartis Vaccines, Germany), inhibit binding of 1F5-HRP to biotinylated rHA1 derived from A/California/06/09 in a competitive EIA, suggesting that the epitope recognized by this Mab also evokes an antibody response in infected ferrets and vaccinated humans.

A randomised, partially observer blind, multicentre, head-to-head comparison of a two-dose regimen of Baxter and GlaxoSmithKline H1N1 pandemic vaccines, administered 21 days apart

OBJECTIVES

To evaluate the immunogenicity of a two-dose schedule of Baxter cell-cultured, non-adjuvanted, whole-virion H1N1 vaccine, and GlaxoSmithKline AS03(A)-adjuvanted split-virion H1N1 vaccine with respect to the EU Committee for Medicinal Products for Human Use (CHMP) and the US Food and Drug Administration (FDA) licensing criteria.

DESIGN

An age-stratified, randomised, observer-blind, parallel-group, multicentre controlled trial was carried out in volunteers aged ≥ 18-44, ≥ 45-64 and ≥ 65 years.

SETTING

Three teaching hospitals in the UK (Leicester Royal Infirmary, Leicester; Nottingham City Hospital, Nottingham; and Royal Hallamshire Hospital, Sheffield).

PARTICIPANTS

Three hundred and forty-seven subjects were identified and randomised to AS03(A)-adjuvanted split-virion H1N1 vaccine or whole-virion (WV) vaccine in age groups [≥ 18-44 years (n = 140), ≥ 45-64 years (n = 136) and ≥ 65 years (n = 71)].

INTERVENTIONS

Vaccine was administered by intramuscular injection into the deltoid muscle of the non-dominant arm. One hundred and seventy-five randomised subjects were allocated AS03(A)-adjuvanted split H1N1 vaccine; one hundred and sixty-nine subjects had a second dose of the same vaccine 21 days later. One hundred and seventy-two subjects were allocated WV vaccine; one hundred and seventy-one subjects had a second dose of the same vaccine 21 days later. Serum samples for antibody measurements were collected on days 0 (before the first vaccination), 7, 14, 21 (before the second vaccination), 28, 35, 42 and 180. Subjects were observed for local and systemic reactions for 30 minutes after each injection, and for the next 7 days they recorded, in self-completed diaries, the severity of solicited local (pain, bruising, erythema and swelling) and systemic symptoms (chills, malaise, muscle aches, nausea and headache), oral temperature and use of analgesic medications.

MAIN OUTCOME MEASURES

Vaccine immunogenicity using the CHMP and the FDA licensing criteria. Antibody titres were measured using haemagglutination inhibition (HI) and microneutralisation (MN) assays at baseline and 7, 14 and 21 days after each vaccination and at day 180. The three immunogenicity criteria end points were the seroprotection rate, the seroconversion rate and the mean-fold titre elevation.

RESULTS

Both vaccine doses were given in 340 subjects (98%). Data from 680 (99%) of 687 issued diary cards were returned. Sera were obtained from 340 (98.0%), 333 (96.0%), 341 (98.3%), 331 (95.4%), 329 (94.8%) and 332 (95.7%) subjects on days 7, 14, 21, 28, 35 and 42, respectively. Three hundred and forty-six and 345 subjects were included in the safety and immunogenicity analyses, respectively. Prevaccination antibody was detected by HI (titre ≥ 1 : 8) and MN (titre ≥ 1 : 10) in 14% and 31% of subjects, respectively. Among the 298 (85.9%) subjects without baseline antibody on HI assay, a titre of ≥ 1 : 40 (seroprotection) was achieved after a single dose of AS03(A)-adjuvanted vaccine and WV vaccine by day 21 in 93.0% and 65.5%, respectively, of subjects between 18 and 44 years, 76.4% and 36.1% of subjects between 45 and 64 years, and 53.1% and 30.0% of subjects ≥ 65 years. Among all 347 subjects, a titre of ≥ 1 : 40 was achieved after a single dose of AS03(A)-adjuvanted vaccine and WV vaccine by day 21 in 94.0% and 71.4%, respectively, of subjects between 18 and 44 years, 77.3% and 38.8% of subjects between 45 and 64 years, and 51.4% and 32.4% of subjects ≥ 65 years. The age-adjusted odds ratio (OR) for adjuvanted compared with WV vaccine, in terms of seroprotection, was 4.42 [95% confidence interval (CI) 2.63 to 7.44, p < 0.001]. On day 42, among subjects without baseline antibody on HI assay, a titre of ≥ 1 : 40 was achieved after the second dose of AS03(A)-adjuvanted vaccine and WV vaccine by 100% and 67.9%, respectively, of subjects between 18 and 44 years, 89.3% and 41% of subjects between 45 and 64 years, and 76.5% and 34.5% of subjects ≥ 65 years. Among all 347 subjects, a titre of ≥ 1 : 40 was achieved on day 42 after the second dose of AS03(A)-adjuvanted vaccine and WV vaccine in 100% and 73.1%, respectively, of subjects between 18 and 44 years, 90.8% and 43.9% of subjects between 45 and 64 years, and 75.7% and 36.4% of subjects ≥ 65 years. The age-adjusted OR for adjuvanted vaccine compared with WV vaccine, in terms of seroprotection, was 11.21 (95% CI 5.80 to 21.64, p < 0.001). Age-related decline in antibody response occurred after both doses of both vaccines. WV vaccine was associated with fewer local and systemic reactions and lower immune responses than was AS03(A)-adjuvanted vaccine. The most frequent solicited local event was pain, reported by 28% and 76% of subjects after either dose of WV or adjuvanted vaccine, respectively (OR 7.71, 95% CI 4.48 to 13.24, p < 0.0001). The most common systemic event was myalgia, reported by 24% and 49% of subjects after either dose of WV or adjuvanted vaccine (OR 2.99, 95% CI 1.86 to 4.80, p < 0.0001).

CONCLUSIONS

AS03(A)-adjuvanted 2009 H1N1 vaccine is more immunogenic and provides greater antigen-sparing capacity than WV 2009 H1N1 vaccine.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN92328241.

FUNDING

This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 14, No. 55. See the HTA programme website for further project information.

Observational study to investigate vertically acquired passive immunity in babies of mothers vaccinated against H1N1v during pregnancy

OBJECTIVE

The primary objective was to determine the proportion of babies who acquired passive immunity to A/H1N1v, born to mothers who accepted vaccination as part of the national vaccination programme while pregnant (during the second and/or third trimesters) against the novel A/H1N1v influenza virus (exposed group) compared with unvaccinated (unexposed) mothers.

DESIGN

An observational study at three sites in the UK. The purpose was to determine if mothers immunised against A/H1N1v during the pandemic vaccination period transferred that immunity to their child in utero.

SETTING

Three sites in the UK [Queen's Medical Centre, Nottingham; City Hospital, Nottingham (both forming University Hospitals Nottingham), and Leicester Royal Infirmary (part of University Hospitals Leicester)].

PARTICIPANTS

All pregnant women in the second and third trimester presenting at the NHS hospitals above to deliver were eligible to participate in the study. Women were included regardless of age, social class, ethnicity, gravida and parity status, past and current medical history (including current medications), ethnicity, mode of delivery and pregnancy outcome (live/stillbirth).

INTERVENTIONS

At enrolment, participants provided written consent and completed a questionnaire. At parturition, venous cord blood was obtained for serological antibody analysis. Serological analysis was undertaken by the Respiratory Virus Unit (RVU), Health Protection Agency (HPA) Centre for Infections, London.

MAIN OUTCOME MEASURES

The primary end point in the study was the serological results of the cord blood samples for immunity to A/H1N1v. Regarding a suitable threshold for the determination of a serological response consistent with clinical protection, this issue is somewhat complex for pandemic influenza. The European Medicines Agency (EMEA) Committee for Human Medicinal Products (CHMP) judges that a haemagglutination inhibition (HI) titre of 1 : 40 is an acceptable threshold. However, this level was set in the context of licensing plain trivalent seasonal vaccine, where a titre of 1 : 40 is but one of several related immunogenicity criteria, and supported by paired sera capable of demonstrating a fourfold rise in antibody titre in response to vaccination. The current study mainly investigated the effects of an AS03-adjuvanted monovalent vaccine, and it was not possible to obtain paired sera where the initial sample was taken before vaccination (in vaccinated subjects). Of possibly greater relevance is the fact that it has been established from the study of early outbreaks of pandemic influenza in secondary schools in the UK (HPA, unpublished observations) that an HI antibody titre of 1 : 32 seems to be the threshold for a humoral response to 'wild-type' A/H1N1v infection. On that basis, a threshold of 1 : 32 is at least as appropriate as one of 1 : 40, especially in unvaccinated individuals. Given the difficulties that would accrue by applying thresholds of 1 : 32 in unvaccinated patients and 1 : 40 in vaccinated patients, we have therefore applied a threshold of 1 : 32 and 1 : 40, to increase the robustness of our findings. Differences arising are described. A microneutralisation (MN) titre of 1 : 40 may be also used, although it is not part of the CHMP criteria for vaccine licensure. Nonetheless, we utilised this analysis as a secondary end point, based on a conservative threshold of 1 : 60.

RESULTS

Reverse cumulative distribution percentage curves for haemagglutinin dilution and MN titres demonstrate background immunity in babies of unvaccinated mothers of 25%-30%. Humoral immunity in babies of vaccinated mothers was present in 80% of the group. The difference in positive immunity between the babies of unvaccinated and vaccinated mothers was statistically significant (chi-squared test, p < 0.001).

CONCLUSIONS

Our findings reveal a highly significant difference in HI titres between babies born to mothers vaccinated with pandemic-specific vaccine against A/H1N1v during the 2009-10 pandemic period. The subjects recruited were comparable from a baseline perspective and thus do not represent different groups that otherwise could have introduced bias into the study. Continued circulation of 2009 A/H1N1-like viruses is uncertain, but is possible as seasonal influenza in years to come. It is possible that future seasonal waves may display increased virulence. Given the adverse outcomes experienced for a small proportion of pregnant women during the influenza pandemic of 2009-10, this study provides useful evidence to support vaccination in pregnancy to protect both the mother and baby.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Assessment of baseline age-specific antibody prevalence and incidence of infection to novel influenza A/H1N1 2009

OBJECTIVES

The objectives of the H1N1 2009 serological surveillance project were twofold: to document (1) the prevalence of cross-reactive antibodies to H1N1 2009 by age group in the population of England prior to arrival of the pandemic strain virus in the UK and (2) the age-specific incidence of infection by month as the pandemic progressed by measuring increases in the proportion of individuals with antibodies to H1N1 2009 by age.

METHODS

Residual aliquots of samples submitted to 16 microbiology laboratories in eight regions in England in defined age groups in 2008 and stored by the Health Protection Agency serological surveillance programme were used to document age-stratified prevalence of antibodies to H1N1 2009 prior to the arrival of the pandemic in the UK. Functional antibodies to the H1N1 2009 virus were measured by haemagglutination inhibition (HI) and microneutralisation (MN) assays. For timely measurement of monthly incidence of infection with H1N1 2009 between August 2009 and April 2010, the microbiology serum collections were supplemented by collection of residual sera from chemical pathology laboratories in England. Monthly seroincidence samples were tested by HI only, apart from the final sera collected post pandemic in 2010, which were also tested by MN. Incidence during the pandemic was estimated from changes in prevalence between time points and also by a likelihood-based method.

SETTING

Eight regions of England.

PARTICIPANTS

Serum samples from patients accessing health care in England from whom blood samples were taken for unrelated microbiological or chemical pathology testing.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Baseline age-specific prevalence of functional antibodies to the H1NI 2009 virus prior to the arrival of the pandemic; changes in antibody prevalence during the period August 2009 to April 2010.

RESULTS

Pre-existing cross-reactive antibodies to H1N1 2009 were detected in the baseline sera and increased with age, particularly in those born before 1950. The prediction of immunological protection derived from the baseline serological analysis was consistent with the lower clinical attack rates in older age groups. The high levels of susceptibility in children < 15 years, together with their mixing within school, resulted in the highest attack rates in this age group. Serological analysis by region confirms that there were geographical differences in timing of major pandemic waves. London had a big first wave among the 5- to 14-year age group, with the rest of the country reducing the gap after the second wave. Cumulative incidence in London remained higher throughout the pandemic in each age group. By the end of the second wave it is estimated that as many as 70% of school-aged children in London had been infected. Taken together, these observations are consistent with observations from previous pandemics in 1918, 1957 and 1968 - that the major impact of influenza pandemics is on younger age groups, with a pattern of morbidity and mortality distinct from seasonal influenza epidemics.

CONCLUSIONS

Serological analysis of appropriately structured, age-stratified and geographically representative samples can provide an immense amount of information to set in context other measures of pandemic impact in a population, and provide the most accurate measures of population exposure. National scale seroepidemiology studies require cross-agency coordination, multidisciplinary working, and considerable scientific resource.

FUNDING

The National Institute for Health Research Health Technology Assessment programme and the Health Protection Agency.

Age-specific incidence of A/H1N1 2009 influenza infection in England from sequential antibody prevalence data using likelihood-based estimation

Estimating the age-specific incidence of an emerging pathogen is essential for understanding its severity and transmission dynamics. This paper describes a statistical method that uses likelihoods to estimate incidence from sequential serological data. The method requires information on seroconversion intervals and allows integration of information on the temporal distribution of cases from clinical surveillance. Among a family of candidate incidences, a likelihood function is derived by reconstructing the change in seroprevalence from seroconversion following infection and comparing it with the observed sequence of positivity among the samples. This method is applied to derive the cumulative and weekly incidence of A/H1N1 pandemic influenza in England during the second wave using sera taken between September 2009 and February 2010 in four age groups (1-4, 5-14, 15-24, 25-44 years). The highest cumulative incidence was in 5-14 year olds (59%, 95% credible interval (CI): 52%, 68%) followed by 1-4 year olds (49%, 95% CI: 38%, 61%), rates 20 and 40 times higher respectively than estimated from clinical surveillance. The method provides a more accurate and continuous measure of incidence than achieved by comparing prevalence in samples grouped by time period.

Open-label, randomised, parallel-group, multicentre study to evaluate the safety, tolerability and immunogenicity of an AS03(B)/oil-in-water emulsion-adjuvanted (AS03(B)) split-virion versus non-adjuvanted whole-virion H1N1 influenza vaccine in UK children 6 months to 12 years of age

OBJECTIVE

To evaluate the safety, tolerability and immunogenicity of an AS03(B)/oil-in-water emulsion-adjuvanted (AS03(B)) split-virion versus non-adjuvanted whole-virion H1N1 influenza vaccine in UK children aged 6 months to 12 years.

DESIGN

Multicentre, randomised, head-to-head, open-label trial.

SETTING

Five UK sites (Oxford, Bristol, Southampton, Exeter and London).

PARTICIPANTS

Children aged 6 months to < 13 years, for whom a parent or guardian had provided written informed consent and who were able to comply with study procedures, were eligible for inclusion.

INTERVENTIONS

A tocopherol/oil-in-water emulsion-adjuvanted (AS03(B)) egg culture-derived split-virion H1N1 vaccine and a non-adjuvanted cell culture-derived whole-virion vaccine, given as a two-dose schedule, 21 days apart, were compared. Participants were grouped into those aged 6 months to < 3 years (younger group) and 3 years to < 13 years of age (older group) and were randomised by study investigators (1 : 1 ratio) to receive one of the two vaccines. Vaccines were administered by intramuscular injection (deltoid or anterior-lateral thigh, depending on age and muscle bulk). Local reactions and systemic symptoms were collected for 1 week post immunisation, and serum was collected at baseline and after the second dose. To assess safety and tolerability, parents or guardians recorded the following information in diary cards from days 0-7 post vaccination: axillary temperature, injection site reactions, solicited and unsolicited systemic symptoms, and medications.

MAIN OUTCOME MEASURE

Comparison between vaccines of the percentage of participants demonstrating seroconversion by microneutralisation assay.

RESULTS

Among 937 children receiving vaccine, per-protocol seroconversion rates were higher after the AS03(B)-adjuvanted vaccine than after the whole-virion vaccine (98.2% vs 80.1% in children < 3 years, 99.1% vs 95.9% among those aged 3-12 years), as were severe local reactions (3.6% vs 0.0% in those under 5 years, 7.8% vs 1.1% in those aged 5-12 years), irritability in children < 5 years (46.7% vs 32.0%), and muscle pain in older children (28.9% vs 13.2%). The second dose of the adjuvanted vaccine was more reactogenic than the first, especially for fever > 38.0°C in those under 5 years of age (8.9% vs 22.4%).

CONCLUSION

The adjuvanted vaccine, although reactogenic, was more immunogenic, especially in younger children, indicating the potential for improved immunogenicity of influenza vaccines in this age group.

TRIAL REGISTRATION NUMBER

ISRCTN89141709.

Immunogenicity and safety of a two-dose schedule of whole-virion and AS03A-adjuvanted 2009 influenza A (H1N1) vaccines: a randomised, multicentre, age-stratified, head-to-head trial

BACKGROUND

Effective antigen-sparing vaccines are needed to confront pandemic influenza. Whole-virion and oil-in-water adjuvanted vaccines are the most effective formulations against H5N1 avian influenza. We assessed the safety and immunogenicity in adults in the UK of pandemic H1N1 whole-virion vaccine and oil-in-water adjuvanted vaccine purchased by the UK government in 2009.

METHODS

In our randomised, observer-blind, parallel-group, controlled trial, healthy adults aged 18-44 years, 45-64 years, and 65 years and older (from Oct 19, to Nov 12, 2009) received two doses of vaccine given 21 days apart: either 7·5 μg of haemagglutinin formulated as whole-virion vaccine, or 3·75 μg of haemagglutinin formulated as split-virion vaccine with AS03(A) oil-in-water adjuvant. Assignment was by a computer-generated code, with random permuted blocks of two, four, and six. All participants and investigators were unaware of vaccine assignments. The trial was done at three hospitals in the UK. We measured antibody titres with a haemagglutination-inhibition assay at baseline; 7, 14, and 21 days after each vaccination; and at 6 months after the first dose. Primary outcome was vaccine immunogenicity of the full analysis set by the EU Committee of Human Medicinal Products licensing criteria. This study is registered with ISRCTN, number ISRCTN92328241.

FINDINGS

At day 0, baseline antibody (titre ≥1/8) was detected in 44 (13%) of 347 participants. Sera from 95% to 98% of participants were assessed for immunogenicity on days 7, 14, 21, 28, 35, and 42, and at 6 months. On day 21 after one dose of adjuvanted AS03(A) or whole-virion vaccine, 63 (94%, 95 CI 85·4-98·4) of 67 and 50 (71%, 59·4-81·6) of 70 participants aged 18-44 years, 51 (77%, 65·3-86·7) of 66 and 26 (39%, 27·1-51·5) of 67 aged 45-64 years, and 19 (51%, 34·4-68·1) of 37 and 11 (32%, 17·4-50·5) of 34 aged 65 years or older had titres of 1:40 or greater. On day 42 (21 days after the second dose), 64 (100%, 94·4-100) of 64 and 49 (73%, 60·9-83·2) of 67 participants aged 18-44 years, 59 (91%, 81·0-96·5) of 65 and 29 (43·9%, 31·7-56·7) of 66 aged 45-64 years, and 28 (76%, 58·8-88·2) of 37 and 12 (36%, 20·4-54·9) of 33 aged 65 years or older had titres of 1/40 or greater. At 6 months, 62 (98%, 91·5-100) of 63 and 54 (78%, 66·7-87·3) of 69 participants aged 18-44 years, 54 (82%, 70·4-90·2) of 66 and 37 (55%, 42·6-67·4) of 67 aged 45-64 years, and 21 (57%, 39·5-72·9) of 37 and 10 (29%, 15·1-47·5) of 34 aged 65 years or older had titres of 1/40 or greater. There were no vaccine-related serious adverse events. Whole-virion vaccine was associated with fewer local and systemic reactions than adjuvanted vaccine.

INTERPRETATION

AS03(A)-adjuvanted vaccine was more immunogenic against pandemic influenza A H1N1 virus than whole-virion vaccine and offers greater antigen-sparing capacity. A two-dose strategy should be considered for older people.

FUNDING

Department of Health, National Institute for Health Research Evaluation, Trials and Studies Coordinating Centre.

Immunogenicity of pandemic (H1N1) 2009 vaccine in children with cancer in the United Kingdom

BACKGROUND

Children with cancer have an increased susceptibility to influenza infection. The objective of this study was to assess the immunogenicity of pandemic (H1N1) 2009 vaccine in children with cancer.

METHODS

Children were recruited from the Royal Marsden Hospital, England, during November 2009. The vaccination schedule consisted of 2 doses of an AS03(B)-adjuvanted vaccine given at days 0 and 21. Serological analysis was performed on blood samples obtained at day 0 and day 42. The primary immunological end point was the seroconversion rate, which was defined as the proportion of subjects with an individual 4-fold increase in hemagglutination inhibition titer and a postvaccination hemagglutination inhibition titer ≥1:32.

RESULTS

Fifty-four children with a median age of 6.3 years (range, 1.4-16.6 years) were vaccinated and had samples taken for serological analysis. Twenty-four (44.4%) of 54 children demonstrated seroconversion. Seroconversion rates were 33.3% (9 of 27) among children with acute lymphoblastic leukemia, 36.4% (4 of 11) among those with lymphoma or other leukemias, 66.7% (6 of 9) among those with brain tumors, and 71.4% (5 of 7) among those with other solid tumors. Seroconversion occurred in 4 (28.6%) of 14 children receiving acute lymphoblastic leukemia maintenance therapy. Univariate analysis showed significantly higher responses among children with solid tumors, compared with those with hematological malignancies (11 [68.8%] of 16 vs 13 [34.2%] of 38; P = .03), and among those not receiving treatment, compared with those receiving treatment (7 [87.5%] of 8 vs 17 [37.0%] of 46; P = .02). Multivariable analysis showed that age, cancer type, and lymphopenia did not influence seroconversion rates.

CONCLUSION

These data suggest that this AS03(B)-adjuvanted pandemic (H1N1) 2009 vaccine can induce limited but useful protective immune responses in children with cancer.

Repeated vaccination is required to optimize seroprotection against H1N1 in the immunocompromised host

BACKGROUND

In 2009 the declaration by the World Health Organization of a global pandemic of influenza-H1N1 virus led to a vaccination campaign to ensure protection for immunocompromised patients. The goal of this study was to determine the efficacy of the 2009 H1N1 vaccine in patients with hematologic malignancies.

DESIGN AND METHODS

We evaluated humoral and cellular immune responses to 2009 H1N1 vaccine in 97 adults with hematologic malignancies and compared these responses with those in 25 adult controls. Patients received two injections of vaccine 21 days apart and the controls received one dose. Antibody titers were measured using a hemagglutination-inhibition assay on days 0, 21 and 49 after injection of the first dose. Cellular immune responses to H1N1 were determined on days 0 and 49.

RESULTS

By day 21 post-vaccination, protective antibody titers of 1:32 or more were seen in 100% of controls compared to 39% of patients with B-cell malignancies (P<0.001), 46% of allogeneic stem cell transplant recipients (P<0.001) and 85% of patients with chronic myeloid leukemia (P=0.086). After a second dose, seroprotection rates increased to 68%, (P=0.008), 73%, (P=0.031), and 95% (P=0.5) in patients with B-cell malignancies, after allogeneic stem cell transplantation and with chronic myeloid leukemia, respectively. On the other hand, T-cell responses to H1N1 vaccine were not significantly different between patients and controls.

CONCLUSIONS

These data demonstrate the efficacy of H1N1 vaccine in most patients with hematologic malignancies and support the recommendation for the administration of two doses of vaccine in immunocompromised patients. These results may contribute towards the development of evidence-based guidelines for influenza vaccination in such patients in the future.

Humoral and cellular immunity to primary H1N1 infection in patients with hematologic malignancies following stem cell transplantation

Limited data are available on immunologic responses to primary H1N1 infection in patients with hematologic malignancies. We present a prospective, case-surveillance study of such patients with real-time polymerase chain reaction (RT-PCR) confirmed H1N1-influenza who presented to our institution between September 2009 and January 2010. Ninety-two patients presented with influenza-like symptoms, and 13 had H1N1 infection confirmed by RT-PCR, including 4 allogeneic stem cell transplant recipients (1 with acute myelogenous leukemia, 1 with chronic lymphoblastic leukemia [CLL], 1 with non-Hodgkin lymphoma, and 1 with chronic myelogenous leukemia), 5 patients with multiple myeloma following autologous stem cell transplantation, 1 patient with multiple myeloma perimobilization, 2 patients with NHL post chemotherapy, and 1 patient with CLL. All 13 patients required hospitalization. Six (43%) were admitted to the intensive care unit (ICU), of whom 4 (67%) died. We evaluated B cell and T cell responses to H1N1 infection prospectively in these patients compared with those in 4 otherwise healthy controls. Within 12 weeks of diagnosis, only 6 of 11 patients developed seropositive antibody titers as measured by hemagglutination-inhibition or microneutralization assays, compared with 4 of 4 controls. H1N1-specific T cells were detected in only 2 of 8 evaluable patients compared with 4 of 4 controls. H1N1-specific T cells were functional, capable of producing interferon γ, tumor necrosis factor α, and CD107a mobilization. Furthermore, CD154 was up-regulated on CD4(+) T cells in 3 of 4 controls and 2 of 2 patients who had both B cell and T cell responses to H1N1. Post-H1N1 infection, 5 of 8 patients developed seasonal influenza-specific T cells, suggesting cross-reactivity induced by H1N1 infection. These data offer novel insights into humoral and cell-mediated immunologic responses to primary H1N1 infection.

Safety and immunogenicity of AS03B adjuvanted split virion versus non-adjuvanted whole virion H1N1 influenza vaccine in UK children aged 6 months-12 years: open label, randomised, parallel group, multicentre study

OBJECTIVES

To compare the safety, reactogenicity, and immunogenicity of an adjuvanted split virion H1N1 vaccine and a non-adjuvanted whole virion vaccine used in the pandemic immunisation programme in the United Kingdom.

DESIGN

Open label, randomised, parallel group, phase II study.

SETTING

Five UK centres (Oxford, Southampton, Bristol, Exeter, and London).

PARTICIPANTS

Children aged 6 months to less than 13 years for whom a parent or guardian had provided written informed consent and who were able to comply with study procedures were eligible. Those with laboratory confirmed pandemic H1N1 influenza or clinically diagnosed disease meriting antiviral treatment, allergy to egg or any other vaccine components, or coagulation defects, or who were severely immunocompromised or had recently received blood products were excluded. Children were grouped by age: 6 months-<3 years (younger group) and 3-<13 years (older group). Recruitment was by media advertising and direct mailing. Recruitment visits were attended by 949 participants, of whom 943 were enrolled and 937 included in the per protocol analysis.

INTERVENTIONS

Participants were randomised 1:1 to receive AS03(B) (tocopherol based oil in water emulsion) adjuvanted split virion vaccine derived from egg culture or non-adjuvanted whole virion vaccine derived from cell culture. Both were given as two doses 21 days apart. Reactogenicity data were collected for one week after immunisation by diary card. Serum samples were collected at baseline and after the second dose.

MAIN OUTCOME MEASURES

Primary reactogenicity end points were frequency and severity of fever, tenderness, swelling, and erythema after vaccination. Immunogenicity was measured by microneutralisation and haemagglutination inhibition assays. The primary immunogenicity objective was a comparison between vaccines of the percentage of participants showing seroconversion by the microneutralisation assay (fourfold rise to a titre of >or=1:40 from before vaccination to three weeks after the second dose).

RESULTS

Seroconversion rates were higher after the adjuvanted split virion vaccine than after the whole virion vaccine, most notably in the youngest children (163 of 166 participants with paired serum samples (98.2%, 95% confidence interval 94.8% to 99.6%) v 157 of 196 (80.1%, 73.8% to 85.5%), P<0.001) in children under 3 years and 226 of 228 (99.1%, 96.9% to 99.9%) v 95.9%, 92.4% to 98.1%, P=0.03) in those over 3 years). The adjuvanted split virion vaccine was more reactogenic than the whole virion vaccine, with more frequent systemic reactions and severe local reactions in children aged over 5 years after dose one (13 (7.2%, 3.9% to 12%) v 2 (1.1%, 0.1% to 3.9%), P<0.001) and dose two (15 (8.5%, 4.8% to 13.7%) v 2 (1.1%, 0.1% to 4.1%), P<0.002) and after dose two in those under 5 years (15 (5.9%, 3.3% to 9.6%) v 0 (0.0%, 0% to 1.4%), P<0.001). Dose two of the adjuvanted split virion vaccine was more reactogenic than dose one, especially for fever >or=38 masculineC in those aged under 5 (24 (8.9%, 5.8% to 12.9%) v 57 (22.4%, 17.5% to 28.1%), P<0.001).

CONCLUSIONS

In this first direct comparison of an AS03(B) adjuvanted split virion versus whole virion non-adjuvanted H1N1 vaccine, the adjuvanted vaccine, while more reactogenic, was more immunogenic and, importantly, achieved high seroconversion rates in children aged less than 3 years. This indicates the potential for improved immunogenicity of influenza vaccines in this age group.

TRIAL REGISTRATION

Clinical trials.gov NCT00980850; ISRCTN89141709.

Incidence of 2009 pandemic influenza A H1N1 infection in England: a cross-sectional serological study

BACKGROUND

Knowledge of the age-specific prevalence of immunity from, and incidence of infection with, 2009 pandemic influenza A H1N1 virus is essential for modelling the future burden of disease and the effectiveness of interventions such as vaccination.

METHODS

In this cross-sectional serological survey, we obtained 1403 serum samples taken in 2008 (before the first wave of H1N1 infection) and 1954 serum samples taken in August and September, 2009 (after the first wave of infection) as part of the annual collection for the Health Protection Agency seroepidemiology programme from patients accessing health care in England. Antibody titres were measured by use of haemagglutination inhibition and microneutralisation assays. We calculated the proportion of samples with antibodies to pandemic H1N1 virus in 2008 by age group and compared the proportion of samples with haemagglutination inhibition titre 1:32 or more (deemed a protective response) before the first wave of infection with the proportion after the first wave.

FINDINGS

In the baseline serum samples from 2008, haemagglutination inhibition and microneutralisation antibody titres increased significantly with age (F test p<0.0001). The proportion of samples with haemagglutination inhibition titre 1:32 or more ranged from 1.8% (three of 171; 95% CI 0.6-5.0) in children aged 0-4 years to 31.3% (52 of 166; 24.8-38.7) in adults aged 80 years or older. In London and the West Midlands, the difference in the proportion of samples with haemagglutination inhibition titre equal to or above 1:32 between baseline and September, 2009, was 21.3% (95% CI 8.8-40.3) for children younger than 5 years of age, 42.0% (26.3-58.2) for 5-14-year-olds, and 20.6% (1.6-42.4) for 15-24-year-olds, with no difference between baseline and September in older age groups. In other regions, only children younger than 15 years showed a significant increase from baseline (6.3%, 1.8-12.9).

INTERPRETATION

Around one child in every three was infected with 2009 pandemic H1N1 in the first wave of infection in regions with a high incidence, ten times more than estimated from clinical surveillance. Pre-existing antibody in older age groups protects against infection. Children have an important role in transmission of influenza and would be a key target group for vaccination both for their protection and for the protection of others through herd immunity.

FUNDING

National Institute for Health Research Health Technology Assessment Programme.

Trial of 2009 influenza A (H1N1) monovalent MF59-adjuvanted vaccine

BACKGROUND

The 2009 pandemic influenza A (H1N1) virus has emerged to cause the first pandemic of the 21st century. Development of effective vaccines is a public health priority.

METHODS

We conducted a single-center study, involving 176 adults, 18 to 50 years of age, to test the monovalent influenza A/California/2009 (H1N1) surface-antigen vaccine, in both MF59-adjuvanted and nonadjuvanted forms. Subjects were randomly assigned to receive two intramuscular injections of vaccine containing 7.5 microg of hemagglutinin on day 0 in each arm or one injection on day 0 and the other on day 7, 14, or 21; or two 3.75-microg doses of MF59-adjuvanted vaccine, or 7.5 or 15 microg of nonadjuvanted vaccine, administered 21 days apart. Antibody responses were measured by means of hemagglutination-inhibition assay and a microneutralization assay on days 0, 14, 21, and 42 after injection of the first dose.

RESULTS

The most frequent local and systemic reactions were pain at the injection site and muscle aches, noted in 70% and 42% of subjects, respectively; reactions were more common with the MF59-adjuvanted vaccine than with nonadjuvanted vaccine. Three subjects reported fever, with a temperature of 38 degrees C or higher, after either dose. Antibody titers, expressed as geometric means, were higher at day 21 among subjects who had received one dose of MF59-adjuvanted vaccine than among those who had received one dose of nonadjuvanted vaccine (P<0.001 by the microneutralization assay). By day 21, hemagglutination-inhibition and microneutralization antibody titers of 1:40 or more were seen in 77 to 96% and 92 to 100% of subjects receiving MF59-adjuvanted vaccine, respectively, and in 63 to 72% and 67 to 76% of those receiving nonadjuvanted vaccine, respectively. By day 42, after two doses of vaccine, hemagglutination-inhibition and microneutralization antibody titers of 1:40 or more were seen in 92 to 100% and 100% of recipients of MF59-adjuvanted vaccine, respectively, and in 74 to 79% and 78 to 83% of recipients of nonadjuvanted vaccine, respectively.

CONCLUSIONS

Monovalent 2009 influenza A (H1N1) MF59-adjuvanted vaccine generates antibody responses likely to be associated with protection after a single dose is administered. (ClinicalTrials.gov number, NCT00943358).

Reproducibility of serologic assays for influenza virus A (H5N1)

Results for clade 1 viruses were more consistent among laboratories when a standard antibody was used.

Hemagglutination-inhibition (HI) and neutralization are used to evaluate vaccines against influenza virus A (H5N1); however, poor standardization leads to interlaboratory variation of results. A candidate antibody standard (07/150) was prepared from pooled plasma of persons given clade 1 A/Vietnam/1194/2004 vaccine. To test human and sheep antiserum, 15 laboratories used HI and neutralization and reassortant A/Vietnam/1194/2004, A/turkey/Turkey/1/2005 (clade 2.2), and A/Anhui/1/2005 (clade 2.3.4) viruses. Interlaboratory variation was observed for both assays, but when titers were expressed relative to 07/150, overall percentage geometric coefficient of variation for A/Vietnam/1194/2004 was reduced from 125% to 61% for HI and from 183% to 81% for neutralization. Lack of reduced variability to clade 2 antigens suggested the need for clade-specific standards. Sheep antiserum as a standard did not reliably reduce variability. The World Health Organization has established 07/150 as an international standard for antibody to clade 1 subtype H5 and has an assigned potency of 1,000 IU/ampoule.

A sensitive retroviral pseudotype assay for influenza H5N1-neutralizing antibodies

BACKGROUND

The World Health Organisation (WHO) recommended the development of simple, safe, sensitive and specific neutralization assays for avian influenza antibodies. We have used retroviral pseudotypes bearing influenza H5 hemagglutinin (HA) as safe, surrogate viruses for influenza neutralization assays which can be carried out at Biosafety Level 2.

RESULTS

Using our assay, sera from patients who had recovered from infection with influenza H5N1, and sera from animals experimentally immunized or infected with H5 tested positive for the presence of neutralizing antibodies to H5N1. Pseudotype neutralizing antibody titers were compared with titers obtained by hemagglutinin inhibition (HI) assays and microneutralization (MN) assays using live virus, and showed a high degree of correlation, sensitivity and specificity.

CONCLUSIONS

The pseudotype neutralization assay is as sensitive as horse erythrocyte HI and MN for the detection of antibodies to H5N1. It is safer, and can be applied in a high-throughput format for human and animal surveillance and for the evaluation of vaccines.