COVID-19 Immunity May Last Up to a Year After Infection

New research suggests that immunity to COVID-19 may last longer than experts previously thought. Early on, researchers stated that natural infection may offer protection from the virus for up to five months. But two new studies now say it could last as long as a year.

The first study conducted by researchers at Washington University School of Medicine in Saint Louis found that antibodies to the virus are detectable for at least 11 months after infection. A second study, conducted by scientists at Rockefeller University in New York City, found that people who recovered from COVID-19 may be protected for up to 12 months later.

The body’s immune response to COVID-19 probably lasts much longer, according to the researchers, but the studies only tested up to 11 and 12 months, respectively. The research looks at blood and tissue samples from patients who caught the virus early in the pandemic.

Both studies were published as preprints, which means that they have not been peer-reviewed. The peer-review process allows for experts to evaluate a scientific paper and look for any flaws in the research or conclusions.

Antibodies May Drop, but Immunity Lasts

In late 2020, reports showed that the levels of antibodies the body made in response to a COVID-19 infection waned quickly. This was widely reported as meaning that immunity was short-lived and that a person who had been ill with the virus could become sick again.

This conclusion did not take into account the fact that antibody levels usually drop after a viral infection. Even after this drop, enough antibodies typically persist to prevent a second bout of disease, one of the study authors Ali Ellebedy, PhD, said in a statement.

“Although it is too early to be certain, our observations are consistent with a durable immune response, similar to that generated by other viral infections,” study author Jackson Turner, PhD, an instructor of pathology and immunology at Washington University School of Medicine, tells Verywell via email.

The Washington University team evaluated blood serum from 77 people who experienced mild COVID-19 infections. They found that there was a rapid drop in antibodies in the first few months after the infection. But this drop then leveled off.

The Rockefeller University group found immunity lasting as long as 12 months in 63 patients who had previously been infected with COVID-19. The antibodies produced by their memory B cells became increasingly more effective at neutralizing the virus that causes COVID-19.

They also looked at the 26 patients within the group who had received either the Pfizer-BioNTech or Moderna COVID-19 vaccines after their infection. They found that vaccination boosted the immunity that was developing naturally after infection. This heightened immunity appears to be good enough that it could protect individuals against COVID-19 variants that are spreading in the United States and globally.   

“What we have seen in preliminary studies is that people who have been infected and then get a booster shot make very strong immune responses and have much higher capacity to neutralize the virus, including variant strains,” Turner says.

You Should Still Get Vaccinated After Infection

Because of the rising number and spread of COVID-19 variants—and because of worry that the immunity provided by past infections and vaccination might not last—vaccine makers are developing booster shots.  

Several variants of the virus have mutations that make them more resistant to the vaccine and to antibodies created by infection with earlier versions of the virus, Turner says.

And while the lasting nature of the body’s response to infection or vaccination shown in these preliminary studies is promising, it may not be as strong in everyone. “The immunity generated against infection is likely to persist even without booster immunizations,” Turner says. “However, that immunity is highly variable among people and may be very low in some individuals. Even if an individual had a strong response to infection, their immunity may not be protective against reinfection, especially against variant strains.”

Therefore, vaccination after a COVID-19 infection is your best line of protection against the virus.

But if people become sick with COVID-19 a second time, it would likely be a milder version of the infection, he adds. “In most cases, a second infection is likely to be milder since there is some pre-existing immunity to help fight off the virus," Turner says. "Getting vaccinated boosts this immunity even further and greatly reduces the risk of re-infection.”

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