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Flu Shot: Big Changes for Next Season

By    |   Friday, 05 June 2015 03:36 PM

The severe 2014-15 flu season has prompted federal health officials to direct vaccine manufacturers to add two new influenza strains to next season's shot formula, to make it more effective, the Centers for Disease Control and Prevention said this week.

Officials said the new formulation should make next season's flu shot a better match to the influenza strains that will be circulating and do a better job of preventing flu cases that this past year’s vaccine, Live Science reports.

This season’s flu shot was disappointingly ineffective: The CDC reported that people who got the shot were just 19 percent less likely to get the flu than people who did not get vaccinated. That’s about a third less protective than offered previous seasons’ shots. During the 2012 to 2013 flu season, for instance, the flu shot reduced the risk of contracting the flu by 56 percent.

The reason: The 2014-15 flu shot was a mismatch between the flu strains included in that vaccine and the strains that were circulating. Most flu illnesses last fall and winte were caused by a viral strain known as H3N2. But about 80 percent of the H3N2 viruses in circulation were different from the H3N2 strain included in the flu shot, the CDC says, because the virus's genetic material changed slightly over time.

As a result, health officials are switching out one of the three strains included in next season's trivalent three-in-one flu shot, and two of the four strains included in the quadrivalent four-in-one flu shot.

The trivalent flu vaccine protects against two influenza A strains, H1N1 and H3N2, and one influenza B strain. For the 2015-2016 flu season, the H1N1 strain and the influenza B strain will remain the same as last season's, but health officials are adding different H3N2 strain, called A/Switzerland/9715293/2013 (H3N2)-like virus, the CDC said.

The quadrivalent flu vaccine protects against the same strains as the trivalent vaccine, as well as an extra influenza B virus.

This past flu season was particularly severe for older adults, who had the highest rate of flu hospitalizations in a decade, the CDC said.

Between October 2014 and April 2015, there were about 322 hospitalizations per 100,000 people among U.S. adults ages 65 and over, the new report found.

Previously, the highest rate of hospitalizations for this age group was 183 flu hospitalizations per 100,000 people, which occurred during the 2012-2013 flu season.

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Federal health officials are directing vaccine manufacturers to add two new influenza strains to next season's shot formula, to make it more effective than this past year's vaccine.
flu, shot, influenza, vaccine, changes, cdc
Friday, 05 June 2015 03:36 PM
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