This year’s early, widespread influenza outbreaks raised questions about the current vaccine’s effectiveness. Today the US Centers for Disease Control and Prevention (CDC) provided an answer. People who have been vaccinated are 62% less likely to become ill enough with flu to see a physician compared with those who have not been immunized, CDC Director Thomas Frieden, MD, said during a press briefing.
“The flu vaccine is far from perfect, but it’s still the best way by far to prevent the flu,” Frieden said. The current vaccine, which protects against 2 A strains of virus and 1 B strain, falls within the “reasonably effective” range of 50% to 70%. The vaccine targets about 90% of all circulating flu viruses, he added.
Last week, 2 deaths in children were reported, bringing the number of pediatric deaths to 20 for the 2012-2013 flu season. Adult deaths are not reported weekly during flu seasons. Even though 47 states reported widespread flu activity last week, Frieden said the number of states reporting much higher than average outpatient visits for flu symptoms decreased to 24 from 29 the previous week. Some regions in southern and southeastern states may have seen the peaks of their flu seasons, he noted. Outpatient visits for flu symptoms have been minimal so far in California, but Frieden said that reflects how viruses travel around the globe.
The vaccine effectiveness estimate is based on data from 1155 children and adults treated for respiratory infections at 5 sites in the US Influenza Vaccine Effectiveness Network between December 3, 2012, and January 2, 2013. About one-third (36%) had positive flu test results; of those, 57% had an A strain and 43% had a B strain.
Among those who tested positive for flu, 32% had been vaccinated; 56% of those who did not have flu had been vaccinated. Even though the flu season is in full swing, Frieden said it’s not too late to get a flu shot. But vaccine may be in short supply: more than 128 million of the 135 million doses available in the United States already have been given.