BALTIMORE — GlaxoSmithKline's influenza vaccine, Fluarix, is noninferior to Sanofi Pasteur's Fluzone in adults aged 18–95 years, Dr. James D. Campbell reported at a conference on vaccine research sponsored by the National Foundation for Infectious Diseases.
The two vaccines were comparable in terms of immunogenicity, tolerability, and safety in a postmarketing study conducted by GSK at the request of the U.S. Food and Drug Administration following the licensure of Fluarix in 2005.
Immunogenicity of both vaccines was lower in adults aged 65 years and older, however, suggesting the need for improved formulations for this population, said Dr. Campbell of the center for vaccine development at the University of Maryland, Baltimore.
The 1,820 adults randomized to either Fluarix or Fluzone had a median age of 68 years, 92% were white, and 59% were women. Approximately two-thirds of each vaccine group were aged 65 years and older. A total of 1,739 subjects—872 of whom received Fluarix and 867 of whom received Fluzone—completed the study protocol.
Local reactions with both vaccines were nearly all mild or moderate, most lasting just a few days. Severe (grade 3) reactions occurred in 0.2% of the group taking Fluarix and 1.4% of those taking Fluzone. Headache and fatigue were the most common general reactions, occurring in 12%–13% with each vaccine. Severe general reactions were equally rare in both groups, at 1.2% with Fluarix and 1.6% with Fluzone. No category of unsolicited adverse events was markedly more common after either vaccine. Serious adverse events occurred in 5% of participants in each group; none of the adverse events were deemed related to the vaccine, Dr. Campbell said.
Immunologic noninferiority was the primary end point, defined by a geometric mean antibody titer (GMT) response to Fluarix not less than two-thirds that of Fluzone, and a less than 10% difference in seroconversion at day 21 between the two vaccines. Fluarix was immunologically noninferior to Fluzone for all three vaccine strains in the study population as a whole and in the elderly subset.
However, both seroconversion and GMT responses to the H1N1 strain were slightly better with Fluarix; Fluzone produced a slightly higher GMT response to the B strain than did Fluarix, but seroconversion rates were similar.
Both types of responses were diminished in the elderly subjects, compared with the entire group, but did not differ by vaccine. Seroprotection is estimated at 82%–98% for both vaccines, Dr. Campbell said.