Should You Get Vaccinated For COVID-19 If You've Already Had It?

A frontline healthcare worker receives the COVID-19 vaccine in London, UK in December 2020. vasilis asvestas/Shutterstock.com

If you’ve already been infected with COVID-19, you may be wondering whether you need to be vaccinated against the virus. The short answer is: yes! Here’s what you need to know. 

The World Health Organization and the US Centers for Disease Control and Prevention have both said the vaccine can be offered to you regardless of whether you already had a COVID-19 infection. The CDC says they made this decision based on the convincing amount of evidence that it's possible to be reinfected with the disease. 

“We don’t know the durability of protection from infection and many of the people getting vaccinated don’t know if they’ve been infected due to the high rates of asymptomatic transmission,” Professor Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine and co-director of the Texas Children’s Hospital Center for Vaccine Development, told IFLScience.

A fair amount of evidence has shown that it’s possible to be infected with COVID-19 twiceAt this current time, however, there are still a lot of things about COVID-19 reinfection we don’t know about. One of the main questions is how long antibodies from an infection last. Some studies have suggested that antibodies to Covid-19 may fade away within two to three months, while others have suggested even mild infections might spark long-term immunity since there’s some evidence of memory T cell responses. In all likelihood, immune memory is likely to differ between people and how harsh the illness is, with more severe cases likely triggering a stronger immune response.

“Our data shows that 90 percent of people previously infected with SARS-CoV-2 have durable immunity – the immune response is there and it stays. But it also means that 10 percent of COVID-19 survivors have weak immune memory and may be vulnerable to a case of recurrent COVID-19 infection in the future, or they may be more likely to infect others,” explained Dr Alessandro Sette, a professor at La Jolla Institute for Allergy and Immunology, also speaking to IFLScience.

“Unfortunately, we currently have no easy way to measure different types of memory T cells and B cells in concert with antibodies,” Sette added. “But even if we knew levels of antibodies and T cells, we don’t have enough information to determine how much is enough to protect individuals from infection and/or severe illness and therefore the default decision would be to get vaccinated."

Granted, it’s also unclear how long the vaccines may end up protecting you either, since the trials have not been long enough to definitively show this, although the data so far is promising. It's been determined that protection from the Pfizer vaccine does not wane for at least two months, while Moderna’s vaccine produces potent antibodies that last for at least three months. It's thought the immunity will end up last for longer than this, but the data isn't available yet. 

“It is likely that vaccination would also boost the levels of immunity acquired by natural immunity," notes Dr Sette. 

There’s also no evidence that having the vaccine is risky for people who’ve already COVID-19. The clinical trials for the Pfizer and Moderna vaccines did not actively recruit people who had already caught the disease, but it's believed that up to 10 percent of participants had had the virus due to the presence of certain neutralizing antibodies. As with everybody else in the trial, the vaccine proved to be safe overall, with very limited side-effects. However, the CDC does suggest that people should wait at least 90 days after infection with COVID-19 “as a precautionary measure until additional information becomes available.”

Unfortunately, not everyone will be instantly offered the opportunity to be vaccinated against COVID-19. It could be argued that those with a prior infection at a lower risk and should be pushed to the back of the queue and not prioritized. As such, the WHO has suggested individuals may wish to defer their own vaccination for up to 6 months "given the limited vaccine supply." While this makes sense in theory, it will most likely be a choice left up to the individual and not enshrined in any rules. 

“As for prioritizing, we don’t have a system in place to operationalize those with a previous infection, so for now probably not a criterion. And at least one half with a previous infection don’t know it,” adds Hotez.

For more information about COVID-19, check out the IFLScience COVID-19 hub where you can follow the current state of the pandemic, the progress of vaccine development, and further insights into the disease.

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