Do You Need the Vaccine if You've Already Had COVID-19?

The first COVID-19 vaccine shots in the US were administered on December 14, 2020, to high-risk health care workers, marking the start of an ambitious immunization program aiming to give every American the option of receiving the vaccine. By April 2022, more than 218 million people in the US had been fully vaccinated. That is over 65% of the US population.

But does that include people who've already been infected with COVID-19—and should they also get the vaccine?

According to the Centers for Disease Control and Prevention (CDC), a previous COVID-19 infection shouldn't rule out a person from getting the vaccine. In fact, as of April 2022, the CDC recommends COVID-19 vaccination for everyone ages 5 years and older, regardless of whether they have previously been infected with COVID-19 and whether they displayed symptoms or not. However, if you currently have COVID-19 or were exposed to someone with COVID-19, you should wait until your quarantine or isolation is over to get vaccinated.

As of April 2022, the Pfizer-BioNTech or Moderna mRNA vaccines are preferred, but the Johnson & Johnson vaccine can be administered in some situations. The Pfizer-BioNTech vaccine is the only one available for people ages 5 years and older.

But Don't People Who've Had COVID-19 Have Immunity?

Yes, sometimes. The problem is that the level of immunity (as determined by the level of antibodies) varies greatly between people who've been previously infected, Stephen Russell, MD, PhD, CEO, and co-founder of Imanis Life Sciences, told Health. "Higher levels of neutralizing antibodies provide better protection against new infection," explained Dr. Russell. "More severe symptoms of infection often lead to higher levels of neutralizing antibodies, while less severe symptoms may lead to lower or no measurable neutralizing antibody production."

In other words, if you had a very mild COVID-19 infection, your immune system may not have formed enough antibodies. But those who experienced a more severe form of the disease may have enough antibodies that stick around. A study published in the Journal of the American Medical Association (JAMA) in February 2022 found that antibodies were present in unvaccinated people up to 20 months after a positive COVID-19 test result.

However, the study also cautions that antibody levels alone are not necessarily correlated with immunity in unvaccinated healthy US adults. So, if you're unvaccinated, you could still get COVID-19 again even if you have antibodies.

How Does the Vaccine Affect People Who've Already Had COVID-19?

Vaccines help the body respond and fight off invaders by training the body to recognize foreign entities.

"The COVID-19 vaccine triggers an immune response to the spike protein—the red 'broccoli stalk'-like projections as depicted on the surface of each virus that we can 'measure' by looking for COVID-19 antibodies after vaccination," Charles Bailey, MD, medical director for infection prevention at Providence St. Joseph Hospital and Providence Mission Hospital in Orange County, California, told Health. These antibodies should be protective for a period of time by preventing or lessening symptoms of a subsequent COVID-19 infection, explained Dr. Bailey.

To determine exactly how long this "period of time" is, researchers have been studying the effectiveness of vaccines in the longer term. A study published in the New England Journal of Medicine in February 2022 found that while two doses of the Pfizer vaccine provided high protection against infection among healthcare workers in the UK, this protection waned after six months. Still, people who had been infected with the virus and received vaccination had high levels of protection more than one year after infection.

When people who've already had COVID-19 get vaccinated, their immunity is effectively topped up, meaning they're protected for longer. The CDC concurs and reports growing evidence from adults and adolescents showing that people who get vaccinated after being infected have increased protection against getting infected again.

And even after people have been vaccinated, additional booster doses are needed to keep immunity up. The CDC website says that staying up to date with your vaccines helps protect you and others. Booster doses are available for fully vaccinated people. As of April 2022, the CDC recommends boosters for everyone ages 12 years and older. Those who received an mRNA vaccine (the Pfizer or Moderna vaccine) are eligible for a booster five months after receiving the last dose in the primary series, and people who received a viral vector vaccine (the Johnson & Johnson vaccine) should wait at least two months before getting the booster.

What if You Have COVID-19 When You're Due To Get the Vaccine?

If you currently have an infection with SARS-CoV-2, the virus that causes COVID-19, and are thinking about getting vaccinated, you may have to hold off for a while before getting the vaccine.

As of March 2022, the CDC recommends that vaccination should be deferred until you've recovered from acute illness (if you're experiencing symptoms) and you've completed the isolation period. For most people, that's five days after the onset of symptoms, provided there's been no fever for at least 24 hours, per CDC guidelines. If you tested positive but don't have symptoms, the CDC still recommends isolating for five days.

Is There a Way To Test How Long Immunity to COVID-19 Lasts?

Yes, by repeatedly measuring patients' neutralizing antibodies. "We can do this every few months using a quantitative neutralizing antibody test, such as a PRNT or IMMUNO-COV™," said Dr. Russell. "These tests measure virus-neutralizing antibodies—the ones that can stop SARS-CoV-2 infection from taking hold and spreading in the body—and evaluate the level, thereby assessing the strength and durability of the person's immunity to COVID-19 over time."

However, if you get an antibody test after receiving the vaccine, the results could come back positive because your body will be producing antibodies in response to the vaccine. In general, though, the CDC does not recommend getting an antibody test to determine if you have immunity to COVID-19 after you've been vaccinated, and it does not recommend getting an antibody test to help you decide whether you should get vaccinated.

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.