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Do you need a flu shot if you got a COVID shot?

The viruses that cause the flu and COVID-19 are different. Here's what you should know.

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For the most up-to-date news and information about the coronavirus pandemic, visit the WHO and CDC websites.

All of the social distancing, mask-wearing and hand washing we did in 2020 paid off by way of a remarkably mild flu season last year. 

Calling the flu activity for the 2020-2021 season "unusually low" despite high levels of testing for it, the US Centers for Disease Control and Prevention reported substantially fewer cases of the flu last year compared to previous years. That's great news, because we warded off what experts feared could be a "twindemic" of coronavirus and influenza – a virus that can be very serious for some people, including young children, older adults and people with certain health conditions, such as asthma and heart disease. 

But what does that mean for this year? While public health measures meant to curb the coronavirus are still in place in many parts of the country, and some people continue to choose to wear masks and limit their social gatherings, we are a more mobile world than we were in fall 2020. And that means more opportunity for the flu to spread.

Read more: Best face masks for 2021

Will flu season be worse this year? 

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Flu vaccines are recommended for most people age 6 months and older. Some people, including young children, are at risk of complications from the flu.

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"Flu is really hard to predict," says Dan Salmon, professor of International Health at the Johns Hopkins Bloomberg School of Public Health. "Flu is a virus that we call a 'sloppy replicator.'" The virus moves from species to species, he says, and the vaccines developed to prevent the flu are made based on scientists' analysis of different flu strains from other parts of the world that have earlier flu seasons. But the lack of flu circulating last year may make this flu season even harder to predict than it normally is, Salmon says. 

Influenza and the coronavirus that causes COVID-19 are two separate viruses, and because of that they require two separate vaccines. So while your COVID-19 shots will protect you against severe disease from the coronavirus, you will need immunity from influenza to prevent severe illness from the flu.

Who's eligible for a flu shot? 

Most people ages 6 months and older should get a flu shot, according to the CDC, including those who are pregnant, where an infection with the flu could harm their developing baby. Exceptions to this recommendation would be if you had a severe allergic reaction to a flu vaccine in the past, or another "contraindication" (medical reason someone shouldn't receive a vaccine or treatment). 

If you're over age 65, your doctor might offer you a higher-dose flu vaccine to give your immune system an extra boost, and the CDC warns older adults shouldn't get the flu vaccine too early (in July or August) because that may leave too much time for immunity to wane. Pregnant people, people with certain medical conditions and older adults shouldn't take the nasal spray vaccine because it contains a live virus.

But typically, you should get whatever flu vaccine is offered and available to you, Salmon says, and the brand or type shouldn't matter.

Additionally, you may get your flu shot with any other vaccine you're scheduled to get, including the COVID-19 vaccine. And who knows -- in the future, it's possible we could have a combination flu/COVID-19 vaccine. In early September, COVID-19 vaccine-maker Moderna announced it was developing a vaccine that combines a booster dose of COVID-19 vaccine with its experimental flu vaccine. It's being tested and isn't available yet, but it could be an important development in health care if it proves effective and COVID-19 becomes a seasonal virus.

3 reasons you should still get the flu shot this year

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The nasal spray vaccine, which contains a live virus, is approved for people ages 2 to 49 years, according to the CDC. However, people who are pregnant, older adults and people with certain medical conditions should get the shot instead, per the CDC.

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Beyond the CDC's recommendation, leaving a window open to infection from another virus could have potentially serious consequences, especially if someone in your household is at-risk of severe disease from either virus.

1. To avoid getting flu and COVID-19 at the same time (yes, that is possible)

"These viruses are two completely different species, so getting vaccinated for one will not protect you against the other," Dr. Daren Wu, chief medical officer at Open Door Family Medical Center, told CNET last year. "What you definitely do not want is the one-two punch of getting both viruses, which is entirely possible."

Even if you're vaccinated against COVID-19, experiencing a mild breakthrough of COVID-19 in tandem with the flu could be miserable.

"You don't want to get the flu and COVID at the same time," infectious disease expert Dr. Sandra Kesh told CNET last year. "That is a situation that we really have to try to prevent. In an older population it would be potentially disastrous; people who are coinfected are going to have a really hard time. And even in younger adults, one of those infectious diseases really knocks you out, but the two together would be very concerning."

Additionally, Dr. Wu argued that getting the flu shot is important because getting sick can lower your immune resistance and make you more prone to other infections. "Our minds are on COVID-19, but getting the flu will lower your immune system and can make you more susceptible to all sorts of secondary infections, including bacterial infections and other viruses such as COVID-19," he said.

2. Flu and COVID-19 symptoms can look similar

Flu and COVID-19 have a lot of overlap in symptoms, which can be really confusing if you start to get sick. However, throughout the pandemic, some people have referred to COVID-19 as "just the flu," which isn't accurate, even if a person experiences cold-like symptoms or mild flu symptoms. The flu and COVID-19 come from two separate viruses. 

"Often, 'flu' is used as this generic term for not feeling good," Salmon says. "But really, it's influenza."

3. To lower the rates of infectious disease

The reality is, we are facing a global pandemic that continues to cause hospitalizations and death, and we need to prepare for the onset of another infectious disease that can be life-threatening at the same time. Public health measures like choosing to get vaccinated even if you are personally not at risk of getting severely sick from COVID-19, washing your hands frequently and wearing a mask indoors can help prevent the transmission of both viruses.

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When one shot isn't enough

Some people have speculated about vaccine fatigue, and facing a public sick and tired of hearing about vaccines and the ever-dramatic booster roll-out in the US. Others may feel that the emphasis on public health for the safety of those around you will spill into the yearly flu seasons, where some people are much more vulnerable to severe disease and death than others. 

Salmon says he hopes the enthusiasm for vaccines people have realized in the wake of COVID-19 will spur similar enthusiasm for flu vaccines. But, he says, "it cuts in both directions," and he fears the polarization surrounding COVID-19 vaccines could have the opposite effect on people's perceptions of vaccines in general. One of the best predictors of whether someone got the coronavirus vaccine was whether they received a flu vaccine in past years, Salmon says. 

Still, there's reason to be hopeful that the lessons we continue to learn in the COVID-19 pandemic will influence actions regarding other viruses. 

"That would be great. That would be the potential that we have here, is that people go, 'wow, vaccines are amazing,'" Salmon says. "Here we have this terrible pandemic and we're able to really make progress through vaccines. And not only protect ourselves, but protect other people."

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.