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AS03 adjuvant enhances immune response to H7N9 vaccine
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The AS03 and MF59 adjuvants appear to bolster immune responses to two doses of an inactivated H7N9 influenza vaccine, with the AS03 adjuvant generating the highest titers, according to recent data.
In the randomized, double blind, phase 2 trial, researchers at five U.S. sites enrolled 980 adults aged 19 years to 64 years from Sept. 18, 2013 to Nov. 22, 2013. Participants were randomly assigned to one of 10 study groups, and were administered various vaccine formulations. The H7N9 vaccine was administered sequentially, given on days 0 and 21 at hemagglutinin doses of 3.75 μg, 7.5 μg, 15 μg, and 45 μg. Vaccines were given with or without AS03 or MF59 adjuvant included in the formulation.
The researchers defined the study’s main outcome as the percentage of participants attaining a hemagglutination inhibition antibody (HIA) titer of 40 or higher at 21 days after receiving the second vaccination. Other main outcomes included serious adverse effects related to the vaccine up to 12 months after the first vaccination, and postvaccination signs or symptoms through day 7.
The researchers found that among most participants, two doses of vaccine were necessary to elicit detectable titers. After two doses of the 15 μg formulation without adjuvant, the percentage of patients who attained a HIA titer of 40 or higher was 2% (95% CI, 0-7). After two doses with the AS03 adjuvant, 85% (95% CI, 76-91) achieved the HIA titer outcome; and after two doses of the vaccine with MF59 adjuvant, 57% (95% CI, 47-68) achieved HIA titer of 40 or higher (P <.001, for comparison of the AS03 and MF59 adjuvant schedules).
On day 21, the groups given two doses of an AS03-adjuvanted vaccine attained the highest hemagglutination inhibition geometric mean titers (GMTs). Two vaccine schedules in which AS03 and MF59 adjuvanted vaccines were alternated yielded lower GMTs (41.5; 95% CI, 31.7-54.4; and 58.6; 95% CI, 44.3-77.6) compared with two doses of AS03-adjuvanted vaccine (103.4; 95% CI, 78.7-135.9), but higher GMTs than a group given two doses of MF59 adjuvanted formulations (29; 95% CI, 22.4-37.6).
"These results imply that, of the options currently available utilizing adjuvants included in the national stockpile, based on the immune response data, AS03 should be considered a first-line adjuvant for strategies incorporating an inactivated H7N9 vaccine in adults," the researchers wrote.
Disclosure: Jackson reports receiving funding from Novavax for the conduct of a clinical trial of an unrelated vaccine. Please see the full study for a list of all other authors’ relevant disclosures.
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