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Adjuvanted H1N1 Vaccine May Beat Whole-Virion Vaccine

Provides a more rapid and stronger immune response

MONDAY, Dec. 20 (HealthDay News) -- An adjuvanted split-virus vaccine appears to provide a more rapid and stronger immune response against pandemic influenza A H1N1 compared to a whole-virion vaccine, according to a study published online Dec. 17 in The Lancet Infectious Diseases.

In an observer-blind, parallel-group, controlled trial, Karl G. Nicholson, of the University of Leicester in the United Kingdom, and colleagues randomized 347 healthy adults aged 18 to 44 years, 45 to 64 years, and 65 years and older (from Oct. 19 to Nov. 12, 2009) to two doses of 7.5 µg of hemagglutinin formulated as whole-virion vaccine given 21 days apart, or two doses of 3.75 µg of hemagglutinin formulated as split-virion vaccine with AS03A oil-in-water adjuvant given 21 days apart.

Compared to the whole-virion vaccine, the investigators found that the adjuvanted vaccine was associated with a significantly higher immune response and higher seroconversion rates, which persisted up to six months after vaccination. In addition, the adjuvanted vaccine was associated with more rapid seroconversion compared to the whole-virion vaccine. Both vaccines were well tolerated and no serious adverse events occurred. However, the adjuvanted vaccine was associated with more injection-site reactions and general symptoms such as muscle pain, chills, headaches, and malaise.

"Despite having half the antigen content of the whole-virion vaccine, the AS03A-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 people in the 18 to 44 years group and more than half of adults of all ages within one 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," the authors write.

Several authors disclosed financial relationships with various pharmaceutical companies and commercial organizations.

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