Can the Flu Shot Protect You from Coronavirus?
It's hard to go anywhere right now without being told that you need to get your flu shot ASAP. Reminders to get vaccinated are plastered all over drugstores, grocery stores, and even on billboards. The Centers for Disease Control and Prevention (CDC) even stresses that getting a flu vaccine this season "will be more important than ever."
Given that this is the first time we'll experience a full influenza season since the coronavirus (COVID-19) pandemic began, it's only natural to wonder if your flu shot can protect you from COVID-19 in some way. Here's what you need to know.
How Does the Flu Shot Work?
Flu vaccines cause antibodies to develop in your body about two weeks after you're vaccinated, according to the CDC. (Reminder: Antibodies are blood proteins that your body forms after being exposed to a particular illness.) The flu shot contains an inactivated (i.e. dead) version of the influenza virus, so you can't get the flu virus from the shot, according to the CDC. (Here are the actual flu shot side effects to watch out for.)
What you can get from the flu vaccine are antibodies to protect you from the flu. Those antibodies can help protect you from getting infected with the strains of the flu that were used to make the vaccine. (Reminder: There are often multiple strains of the flu circulating each year, hence why multiple strains are used to make the vaccine.)
The effectiveness of the flu vaccine varies. Last year it was about 39 percent effective at preventing the flu, but it's been up to 60 percent effective in past years. Keep in mind, though, that the CDC says that even if you do get the flu after you've been vaccinated, the vaccine can help lower the risk of developing serious complications from the flu.
So, Can the Flu Shot Protect You from COVID-19?
Put simply, no, the flu shot will not protect you from getting SARS-CoV-2, the virus that causes COVID-19. "The influenza vaccine only protects against influenza virus and, more narrowly, specific types of flu virus that are included in that year's vaccine," says David Cennimo, M.D., assistant professor of medicine-infectious disease at Rutgers New Jersey Medical School. "The SARS-CoV-2 coronavirus is too different from the influenza virus to get cross-protection from the vaccine." (Here's what you need to know about FluMist, the flu vaccine nasal spray.)
"COVID-19 is caused by SARS-CoV-2, a novel coronavirus that is structurally different from the influenza virus," adds Richard Watkins, M.D., an infectious disease physician and professor of internal medicine at the Northeast Ohio Medical University. "The antibodies the human immune system makes after receiving the flu vaccine don't recognize SARS-CoV-2."
While the CDC has an entire section on its website devoted to COVID-19 and the flu, the agency also notes in an FAQ page: "Getting a flu vaccine will not protect against COVID-19, however flu vaccination has many other important benefits."
Why It's Still Important to Get Your Flu Shot This Year
For starters, it's possible to have the flu and COVID-19 at the same time. In California, the first known case of flu and COVID co-infection was recently confirmed by local health officials. The Solano County Department of Health and Social Services offered few details about the unnamed individual, though the San Francisco Chronicle reports that the person is under 65, "otherwise healthy," and has recovered from the co-infection. The CDC notes that health experts are currently studying how common flu and COVID co-infection might be in the general population.
While the California case involved a person who reportedly recovered from their co-infection, experts say it's generally not an ideal scenario to have COVID-19 and the flu at the same time. "Patients with both viruses could do much worse [than those with just one virus]," says Dr. Cennimo.
The flu and COVID-19 can also cause similar symptoms — fever, fatigue, dry cough, shortness of breath — which can make it tricky for doctors to properly diagnose what you might be dealing with if you become sick, adds Dr. Watkins. "It is very challenging to differentiate the symptoms caused by influenza and COVID-19," he explains. "So, if you get the flu vaccine, then get a flu-like illness, it seems the likelihood it is COVID-19 would be higher."
Plus, if you don't get the flu shot and then come down with the flu, that in itself could possibly put you at risk of not only getting COVID-19 but also of developing severe complications from the virus, says Dr. Cennimo. In that case, "your system is already weakened from the initial insult" of the flu, he explains. Meaning, "the flu may leave you more susceptible to a COVID-19 infection," he says. (Related: Here's Everything You Need to Know About Coronavirus and Immune Deficiencies)
The CDC also points out that getting your flu vaccine can help conserve potentially scarce healthcare resources. Hospitals and doctors' offices may be inundated with more patients as we get deeper into cold and flu season (and, possibly, another wave of COVID-19 in certain parts of the world), so by protecting yourself from the flu, you're potentially reducing the strain on the healthcare system as it responds to both influenza and COVID-19. (Related: What It's Really Like to Be an Essential Worker In the U.S. During the Coronavirus Pandemic)
For the record, experts say it's important to state this, too: There is no evidence that getting a flu vaccine increases your risk of getting sick from COVID-19.
That said, you might have heard about a study published in January that suggested a link between getting the flu vaccine and an increased risk of contracting four commonly circulating seasonal coronaviruses (but not the one that causes COVID-19), which can cause your typical common cold. However, follow-up research later found that getting the flu vaccine does not appear to increase the risk of getting seasonal coronaviruses. Researchers in the follow-up analysis pointed out multiple design flaws with the original study, including the fact that the initial study only analyzed data from a single flu season. The follow-up research included data from seven flu seasons, and when researchers re-examined the results with these improved methods, they found that getting a flu vaccine did not appear to increase the risk of infection with other seasonal coronaviruses. While the latter research still didn't examine the link between the flu shot and COVID-19, specifically, the study authors noted that their findings "provide reassurance against the speculation that influenza vaccine may negatively affect COVID-19 risk."
When to Get Your Flu Shot
The CDC recommends getting your flu shot before flu viruses begin spreading in your community. While you can technically get a flu shot at any point once vaccines are available, the CDC specifically states that it's best to get your shot by the end of October. (See: When Is the Best Time to Get a Flu Shot?)
But, experts say, getting your flu shot whenever you can is ultimately what's important. "Everyone should get a flu vaccine every year," says Dr. Cennimo. "These unknowns and risks of the pandemic make that recommendation even more urgent."
The information in this story is accurate as of press time. As updates about coronavirus COVID-19 continue to evolve, it’s possible that some information and recommendations in this story have changed since initial publication. We encourage you to check in regularly with resources such as the CDC, the WHO, and your local public health department for the most up-to-date data and recommendations.