One part of the flu vaccine may be all it takes to make the shot not as strong as expected.
According to new research, the part of the shot that combats the strain of the flu called H3N2 has cut the risk of infection by 38 percent recently, the Boston Globe reported.
The vaccine, however, does have stronger protection against H1N1 and influenza B, cutting the risk of those strains by 60% to 75%.
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H3N2 viruses can be severe and when they dominate, the flu season can be severe, the Globe reported.
The recent findings were presented at IDWeek, a meeting of infectious disease experts.
The Centers for Disease Control and Prevention suggests that everyone 6 months and older get a flu shot as soon as it becomes available.
Get more tips on staying healthy this season here.