Flu strains change from year to year. This means that the flu shot you get every year is always something of a risk. The World Health Organization consults with experts around the globe twice a year to inform its recommendations on which strains are targeted by shots in the Northern Hemisphere and Southern Hemisphere. Experts’ predictions aren’t always perfect, which is why flu shot efficacy varies depending on the season.
Preliminary data published by the U.S. Centers for Disease Control and Prevention (CDC) suggests this year’s gamble may pay off. Flu shots used during the beginning of the Southern Hemisphere’s flu season—spring and summer in the Northern Hemisphere—did a good job of keeping people out of the hospital, which suggests the same may be true during the U.S.’s looming fall and winter flu season.
Flu vaccines prevented about half of all possible influenza-related hospitalizations among young children, older adults, and people with preexisting conditions—three groups at increased risk of severe disease—during the first months of the flu seasonin five South American countries, according to the CDC report. That’s based on data about…