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AS03 adjuvant improved immune response of 2009 H1N1 flu vaccine
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In the inactivated 2009 H1N1 influenza vaccine, the AS03 adjuvant system improved immune response in younger and older adults, recent data suggest.
Researchers from the Group Health Research Institute in Seattle studied the immunogenicity and safety of the vaccine with and without AS03 adjuvant system. Adults aged 18 years and older were randomly assigned to one of five vaccine formulations with different hemagglutinin dosages. The formulations included 3.75 mcg, 7.5 mcg or 15 mcg with AS03 or 7.5 mcg or 15 mcg without adjuvant. Participants received two doses of the vaccine.
The study included 544 adults aged younger than 65 years and 245 adults aged at least 65 years. Among adults aged younger than 65 years, at day 21 after the first dose, the hemagglutinin inhibition antibody geometric mean titers (GMTs) were higher in the groups that received the 15-mcg dose with AS03 compared with the 15-mcg unadjuvanted group. After the second dose, hemagglutinin inhibition antibody GMTs increased even more and were higher in all three of the adjuvanted groups vs. the 15-mcg unadjuvanted group.
The hemagglutinin inhibition antibody GMTs were lower in the group aged at least 65 years compared with the group aged younger than 65 years. At day 21 after the first dose and after the second dose, the hemagglutinin inhibition antibody GMTs were higher among those who received the 7.5-mcg and 15-mcg doses with AS03 vs. the 15-mcg unadjuvanted dose. Local adverse events were more common in the groups receiving the AS03, but severe reactions were uncommon.
“As with several other evaluations of 2009 H1N1 vaccines, our results suggest that prior receipt of seasonal influenza vaccine is associated with a lower response to 2009 H1N1 vaccine,” the researchers wrote. “Mechanisms for this immunologic interference have been postulated, but its occurrence and impact, if any, on protective efficacy requires further investigation.”
Disclosure: The researchers report financial relationships with GlaxoSmithKline, Novartis, Pharmajet and Sanofi-Pasteur.
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