Vaccines with two strains of influenza may be more effective in children, research team says

ST. LOUIS Vaccines likely would work better in protecting children from flu if they included both strains of influenza B instead of just one, a St. Louis University press report stated last week, citing research conducted through its Center for Vaccine Development.

"Adding a second influenza B virus strain to the seasonal influenza vaccine would take some of the guesswork out of strain selection and help improve the vaccine's ability to prevent influenza," stated Robert Belshe, lead investigator and director of the center. "Since in five of the last 10 years, the influenza B component in the vaccine has been the incorrect one, this seems like an obvious advance to me."

Every spring, scientists predict which strain of influenza will be circulating in the community the following fall. Historically, they choose two different subtypes of influenza A and one of influenza B.

Research findings in the March issue of Vaccine highlight the importance of adding both lines of influenza B into the vaccine to better protect against the flu, Belshe noted.

The research team examined how well current vaccines protect against influenza B by looking at the immune response of ferrets that were given FluMist, a live attenuated influenza vaccine manufactured by MedImmune.

When ferrets were vaccinated against influenza, the ferrets that were exposed to a strain of influenza B virus that did not match what was in the vaccine didn't have a strong antibody response. However they had a vigorous antibody response when given a vaccine that contained both strains of influenza B.

This showed that immunizing against one strain of influenza B does not appear to protect against the other strain and that a vaccine containing both influenza B strains is likely to offer greater protection from flu.

"These data highlight the need for vaccination strategies that provide enhanced protection against both lineages of influenza B," Belshe said.

The study was sponsored by MedImmune. Belshe has served as a consultant and as part of the speakers bureau for MedImmune and other study authors are MedImmune employees.