Should You Get a Flu Shot After Getting the Flu?
Why you may still need the vaccine even if you've already had the virus this season
The flu season had an early start this year, with waves of cases spiking early in the fall, particularly in the Southeast. If you’re one of the 2.8 million people the Centers for Disease Control and Prevention estimates have already had the flu this year, and you got sick before you had a chance to get your annual flu shot, you may think there’s no point in getting the vaccine now.
But you’d be wrong.
For one thing, you may think you’ve had the flu, but unless you got tested to confirm what was causing your illness, you may have had another bug. It’s easy to confuse the flu with a number of other respiratory viruses that commonly circulate during the flu season, including COVID-19 and RSV.
What’s the Risk From a Second Bout of the Flu?
Although it’s still important to get vaccinated even if you’ve had a case of the flu already, catching one strain of it does give you some limited protection against other strains. It’s the kind of protection that might, for example, limit the severity of illness if you do get the flu a second time.
“There’s some cross-reactivity and cross-immunity, but it’s not the kind of immunity that would prevent you from getting infected,” Topham says.
The overall risk of catching the flu a second time is probably low. A study out earlier this year in the journal Epidemiology & Infection, which examined flu surveillance data in Queensland, Australia from 2005 to 2017, found that the phenomenon was quite rare. (The researchers noted that they could be underestimating the amount of single-season reinfections, however, because people may not have become sick enough during both their illnesses to go to a doctor and get tested.)
Most of these cases involved someone getting a case of flu A and then later a case of flu B (or vice versa). Rarer were cases in which people got two different strains of flu A (and the researchers found no instance of someone getting two different strains of flu B).
So far this flu season in the U.S., most samples tested for their strain have been flu A H3N2, according to the CDC. But different flu types and strains can rise and fall throughout a season, so more flu B could be on its way. And the Queensland study suggests that if a flu B wave is coming, it might increase the risk of reinfection.
So Get That Flu Shot
The bottom line: If you haven’t had one yet, get a flu shot even if you already had the flu (or a bug you think might have been the flu). Although the vaccine doesn’t guarantee that you’ll avoid a second case of the flu, it will reduce the likelihood of reinfection and its potential complications.
If you did get the vaccine this season, there’s no need to get a second one. Scientists say the protection usually lasts for the whole season.
But if you’re still getting over a respiratory illness—or any kind of bug—wait until you’re fully recovered before going for the flu shot, Topham says. That will allow your immune system to return to its regular working order, so that your body can produce a strong response to the vaccine.
And keep in mind that if you’re starting to recover from the flu and symptoms worsen again, this could signal a secondary infection such as pneumonia, and you should call your doctor right away.
Your hygiene habits can also help stop the spread of the flu. Wear a mask in crowded indoor settings. Remember to be diligent about washing your hands and covering any coughs or sneezes. Avoid touching your eyes and mouth to keep from transferring any germs that may be on your hands. Keeping the air at 40 percent to 60 percent humidity by using a humidifier can help, too; dry air helps the flu virus live longer. If you do get sick again, stay home to avoid infecting anyone else.
