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Adjuvanted split-virus H1N1 vaccine elicits better response vs. whole-virus vaccine

Nicholson K. The Lancet. doi:10.1016/S1473- 3099(10)70296-6.

Based on the results of the first head-to-head comparison of two 2009 H1N1 influenza vaccines in adults, increased immunogenicity was observed for the adjuvanted split-virus H1N1 vaccine when compared with the whole-virus vaccine. Conversely, the adjuvanted vaccine was associated with more systemic and local adverse events.

Researchers from the U.K. set out to assess the safety and immunogenicity of the two vaccines and examine the antibody response to the first and second dose of either vaccine.

The study included 347 healthy adults, aged 18 to 44 years, 45 to 64 years and 65 years and older. Participants were randomly assigned to either two doses of 3.75 mcg of hemagglutinin formulated as the adjuvanted vaccine (GlaxoSmithKline) or 7.5 mcg of hemagglutinin formulated as the whole-virus vaccine (Baxter).

Both vaccines were administered 21 days apart during 2009. Antibody titres were measured using a hemagglutination-inhibition assay at baseline, 7, 14, and 21 days after each dose; and at 6 months after the first dose, according to the researchers.

Primary outcome measure was immunogenicity as according to criteria from the European Union's Committee of Human Medicinal Products licensing criteria.

The adjuvanted vaccine produced a significantly higher immune response and achieved more rapid seroconversion rates vs. the whole-virus vaccine. However, the whole-virus vaccine was associated with fewer local and systemic reactions when compared with the adjuvanted vaccine.

Immune response was increased in those aged 18 to 44 — 75% of which achieved seroprotection within 1 week of the first dose.

“Our findings provide clear evidence for the increased immunogenicity of the adjuvanted split-virus vaccine compared with whole-virus vaccine, but also of increased reactogenicity, with more common local and systemic reactions in children and adults.”

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