Adjuvanted HINI vaccine induces a more rapid and stronger immune response than whole-virus vaccine, particularly in young adults

December 16, 2010

A head to head trial of the two H1N1 vaccines given to adults during the 2009 pandemic finds that the adjuvanted split-virus vaccine achieved a more rapid and stronger immune response than the whole-virus vaccine. Furthermore, the findings published Online First in The Lancet Infectious Diseases, suggest that a single dose of the adjuvanted vaccine should be sufficient in adults and adolescents, but for older people two doses might be required.

The study is the first to directly compare two of the commercially available H1N1 vaccines in adults, and concurs with the UK Department of Health decision to use the adjuvanted vaccine as the primary vaccine during the recent pandemic.

Effective vaccines are needed to minimise the effects of pandemic influenza. However, few studies have been done to directly compare H1N1 vaccines to guide future vaccine strategies. Two influenza A 2009 H1N1 vaccines were purchased by the UK Government for the national immunisation programme--a non-adjuvanted whole-virus vaccine and an adjuvanted split-virus inactivated vaccine*.

In this study, a team of UK researchers led by Karl Nicholson from the University of Leicester compared the safety and immune response generated by these two vaccines against influenza A H1N1 during the second wave of the 2009 pandemic.

Between October 2009 and November 2009, 347 healthy adults were enrolled from three hospitals in the UK. Participants were grouped by age (18󈞘 years, 45󈞬 years, and 65 years and older) and randomly assigned to two doses of either the adjuvanted-virus vaccine or the whole-virus vaccine, 21 days apart. Blood samples were taken before vaccination and at weekly intervals after each dose to measure changes in antibody levels.

The adjuvanted vaccine induced a significantly higher immune response and achieved higher seroconversion rates (rises in antibody levels) than the whole-virus vaccine in all age groups, and this seroprotective effect persisted up to 6 months after vaccination.

The adjuvanted vaccine also achieved more rapid seroconversion than the whole-virus vaccine. Immune responses were strongest in young adults with 75% of all 18󈞘 year olds achieving seroprotection within one week of the first dose.

Both vaccines were well tolerated with no vaccine-related serious side effects. However, the adjuvanted vaccine produced more injection-site symptoms and general symptoms (muscle pain, chills, headaches, and malaise) than the whole-virus vaccine.

The authors say: "Despite having half the antigen content of the whole-virion vaccine, the ASO3A adjuvanted split-virion vaccine was more immunogenic than the whole-virion vaccine in all-age groups. The adjuvanted vaccine induced early seroprotection in three-quarters of young adults and more than half of adults of all ages within 1 week of the first dose. This rapid protection could be crucially important in populations such as at-risk groups, or when giving the vaccine coincides with escalating disease activity."

They conclude: "With limited vaccine production capacity, dose-sparing squalene-containing adjuvanted vaccine can optimise coverage."

In a Comment, Geert Leroux-Roels and Isabel Leroux-Roels from Ghent University Hospital, Ghent, Belgium, say: "The ultimate question that remains is whether higher antibody responses as recorded in the study by Nicholson and colleagues translate into superior protection. Comparison of vaccine effectiveness data in countries where different H1N1 pandemic vaccines have been used side by side in comparable populations will hopefully shed some light on this important issue."
Professor Karl Nicholson, University of Leicester, Leicester, UK. T) +44 (0)116 2586164 E)

Dr Geert Leroux-Roels, Ghent University Hospital, Ghent, Belgium. E)

For full Article and Comment, see:

Notes to Editors: * Combining a vaccine with an oil-in-water emulsion (adjuvant) has been shown to produce many more influenza virus antibodies than a non-adjuvanted vaccine with the same dose.



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