Most of us know the flu vaccine isn't 100 percent effective, meaning it’s still possible to get the flu after you get the vaccine. But the exact efficacy is different every year and depends on how well the strains in the vaccine are matched to the ones actually floating around and making people sick.
This year, the vaccine strains and the strains circulating are pretty well-matched so far, according to new data from the Centers for Disease Control and Prevention (CDC).
A different flu vaccine is created each year to try to protect against particular strains of the flu. To determine which strains should be in the vaccine, scientists monitor changes in globally circulating flu strains and use that information to predict which strains are likely to be the most common during the next flu season, explains the National Institute of Allergy and Infectious Diseases (NIAD). They then come up with a vaccine that’s designed to protect against three or four of the strains they think will be the most dominant during that season.
Sometimes the strains in the vaccine aren’t a great match for the ones that end up dominating that season, and sometimes they are, NIAD says. That’s why you can end up with flu vaccine effectiveness that varies from year to year. Effectiveness in recent years has ranged from 60 percent in the 2010-2011 season to 19 percent in the 2014–2015 season, according to CDC data. The past two seasons have been around 40 percent effective—not terrible, but not amazing.
But, so far this year, influenza A(H1N1)pdm09 viruses have dominated in most areas of the country, while influenza A(H3) viruses have caused most flu cases in the southeastern U.S., the CDC says in the latest Weekly U.S. Influenza Surveillance Report. And this year’s vaccine targets H1N1-type, H3N2-type viruses as well as a B-strain, per the CDC, which suggests there's a pretty good match between which strains experts predicted we'd see and what's actually out there.
“When the circulating strains match the shot, that means that we’ll get the optimal effectiveness of the vaccine,” infectious disease expert Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security, tells SELF. By sharing this information now, Dr. Adalja says he hopes that people who haven’t gotten vaccinated against the flu yet will actually do it. (For the record, flu season tends to peak in February but it can run through May.)
The flu vaccine should be your first line of defense, but there are other things you can do to protect yourself and those around you.
All this great news doesn’t mean you still can’t get the flu if you get the vaccine (unfortunately, you can), but the odds are better than if the vaccine wasn’t as great a match.
Plus, "the vaccine is under-appreciated because even if you happen to get the flu, your illness tends to be less severe and you’re less likely to get complications (like pneumonia) and die," William Schaffner, M.D., an infectious disease specialist and professor at the Vanderbilt University School of Medicine, tells SELF. "When people who got vaccinated complain that they still got the flu, my response is always, 'Well, I’m glad you’re still here to complain about it.'"
If someone in your house happens to come down with the flu—whether or not they were vaccinated—there are a few things you can do to lower the odds you’ll be next. Of course, your first step should be getting your vaccine if you haven't already. But, in addition, good hand hygiene is crucial, Dr. Adalja says, along with doing what you can to avoid getting coughed and sneezed on (which is easier said than done if it’s your kids who have the flu). That’s why Dr. Schaffner says it’s not a terrible idea to wear a face mask around your house if you can.
Also, if you happen to be at a higher risk for developing complications from the flu—like if you're pregnant, have diabetes, or have an underlying heart or lung disease—call your doctor. They may recommend that you take the antiviral medication Tamiflu prophylactically to try to prevent you from getting the flu or developing serious complications from it.
Overall, experts still stress that the vaccine is your best protection against the flu. “The flu is taking off all over the country, and if you haven’t been vaccinated, please run—do not walk—and get vaccinated today,” Dr. Schaffner says. “It’s not too late.”