Main Finding: One dose of adjuvant vaccine may protect young children against 2009 H1N1 influenza.
Data Source: A randomized trial of three dosing regimens of H1N1 vaccines, including 194 children aged 3-8 years.
Disclosures: The study was sponsored by Novartis, which manufactured the vaccines used. Study coauthor Dr. Kelly Lindert is an employee of Novartis Vaccines and Diagnostics in Cambridge, Mass.
A single dose of a 7.5-mcg adjuvant vaccine met immunogenicity criteria for protection against the 2009 H1N1 influenza in children aged 3-8 years, based on preliminary data from 390 children in one study.
“The use of adjuvant may provide a rapid immune response at a lower hemagglutinin dose than that required in vaccine without adjuvant,” said Dr. Adriano Arguedas of the Instituto de Atención Pediátrica in San José, Costa Rica, and associates.
They conducted a randomized trial of three dosing regimens of H1N1 vaccines in individuals aged 3-64 years, including 194 children aged 3-8 years and 196 children aged 9-17 years.
The children were randomized to receive one 7.5-mcg hemagglutinin dose with adjuvant, one 15-mcg hemagglutinin dose without adjuvant, or two 15-mcg hemagglutinin doses without adjuvant (N. Engl. J. Med. 2009 Dec. 30 [doi: 10.1056/NEJMc0909988
At 22 days after vaccination, hemagglutinin-inhibition (HI) titers had increased in both age groups for all three vaccine regimens.
After a single dose of each vaccine, children aged 9-17 years met the Food and Drug Administration's Center for Biologics Evaluation and Research (CBER) criteria for immunogenicity, but “in children 3-8 years of age, only the 7.5-mcg dose of 2009 H1N1 vaccine with adjuvant met both the immunogenicity criteria after one dose,” Dr. Arguedas and colleagues wrote.
Neither one nor two 15-mcg doses of unadjuvanted vaccine met the immunogenicity criteria in this younger age group.
According to the CBER criteria, immunogenicity is reached when the lower bound of the two-sided 95% confidence interval was at least 40% in individuals who showed seroconversion on HI assays, and when the lower bound of the two-sided 95% confidence interval was at least 70% in individuals with an HI antibody titer of at least 1:40.
No serious adverse events related to the vaccine were reported in any of the age groups.
The study is ongoing, but the results suggest that use of an adjuvant vaccine could accelerate the process of vaccinating young children (a high-risk group) against H1N1 influenza, the researchers said.