(HealthDay News) — Having acknowledged that the 2014–15 flu vaccine was mismatched to the circulating influenza strains, U.S. health officials have strengthened next season’s vaccine for broader protection.

Components of the coming “2015–16 season vaccine have been changed to more optimally match circulating viruses,” the U.S. Centers for Disease Control and Prevention said in its June 5 Morbidity and Mortality Weekly Report. Last year, it was not recognized until summer that the H3N2 strain would predominate, CDC epidemiologist Lynnette Brammer, MPH, told HealthDay. Work on the vaccine had begun in February. “[The H3N2 strain] came on so fast, and there wasn’t time for it to be included in the vaccine,” she explained. As a result, vaccines were only 18.6% effective against the predominant H3N2 strain.

Vaccines for the coming flu season will contain two influenza type A viruses – H1N1, which caused the 2009 pandemic flu, and last year’s virulent H3N2 – plus an influenza B component, according to the CDC researchers. These are the strains that appear to be circulating in the United States and around the world, and they’re expected to be the main strains in the 2015–16 flu season, Brammer said.

As CDC experts looked back on the flu season that just ended, they described it as moderately severe. Hundreds of thousands of people were hospitalized, and thousands died, most of them aged ≥65. Deaths from flu ranged from 5–9.3% of all deaths between January 3 and Februry 21, 2015. That’s about average for an H3N2 flu year, Brammer said. Pediatric deaths were on the high side. The CDC said 141 children died in 40 states. Child deaths usually range from 34–171 in a given flu season. The biggest exception was the pandemic 2009–10 season, when 358 children died from flu. The CDC recommends that everyone aged ≥6 months get a flu shot every year. Brammer said this year’s vaccine will be available in September.

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