Fact-checking: Do you need a vaccine against COVID-19 if you already had the virus?


Cases of COVID-19 continue to be registered daily in the U.S. and vaccines are on the horizon.

PFizer/BioNTech and Moderna are leading the way in the development of FDA-approved vaccines, with Pfizer showing an efficacy rate of 95 percent and Moderna 94.1 percent. As of December 1, no vaccine had been approved in the U.S., but both developers filed for emergency approval with the Food and Drug Administration (FDA) in late November. Both companies stated that their vaccines will require an initial dose and a booster a few weeks later.

The Question

With vaccines on the horizon, people are now asking whether vaccination is necessary if they have already been diagnosed with COVID-19.

Since the first outbreak of coronavirus in the U.S. earlier this year, about 13.6 million cases have been reported nationwide, according to the Centers for Disease Control (CDC). But are coronavirus antibodies strong enough to confer immunity to a person previously diagnosed with COVID-19 immunity to the virus?

The CDC website suggests that early evidence suggests that coronavirus antibodies “may not last very long. However, they cannot comment on this issue until a vaccine is available and they receive recommendations from the Advisory Committee on Immunization Practices (ACIP).

The facts

On December 2, Operation Warp Speed (OWS), a public-private partnership of the government to facilitate the development, production and distribution of 300 million safe doses of COVID-19 vaccine by January, held a briefing on the coronavirus pandemic.

Dr. Moncef Slaoui, Scientific Director of OWS, referred to the ongoing vaccine studies and how they have impacted participants.

“Here are the facts. In the studies, people were recruited who did not have COVID, the clinical COVID disease, i.e. symptoms etc.,” said Slaoui. “They were recruited on this basis, and it turned out that between 5 and 10 percent of the recruited subjects were zero positive for COVID-19. In other words, they most likely had an asymptomatic or very mildly symptomatic disease and did not notice it.

“So what we do know is that the vaccines are safe in these populations and that a fairly significant number of zero-positives have been vaccinated and their immune responses are being analyzed.

#OperationWarpSpeed is working to accelerate the timetable for the production of a vaccine against COVID19 while maintaining essential standards for safety and efficacy. Stay up-to-date with the latest news: https://t.co/XOIyj4IL6g #OWS pic.twitter.com/k6GMGab1Sv

– HHS.gov (@HHSGov) December 3, 2020

Dr. Mark Siedner, an infectious disease clinician and clinical epidemiologist at Massachusetts General Hospital, agreed that there is not enough evidence to know whether vaccination will benefit those with a past infection.

“On the one hand, we know that some people, especially those with a poor immune system, appear to remain at risk for re-infection,” Siedner told Washington Newsday. “But on the other hand, reinfection seems to be an incredibly rare phenomenon. There are only a handful of cases in the literature”.

It is expected that the first batch of coronavirus vaccines, once approved, will be sufficient for 20 million people, less than the number of people on the front lines and high-risk individuals in the country.

“The decision whether or not to vaccinate those previously infected has a completely different impact on the two groups at the top of the vaccination priority list: the elderly in long-term care facilities and health care workers,” Siedner said. “For the former, vaccination is primarily intended to prevent serious diseases. For the latter, however, vaccination is most important to prevent transmission to others”.

This is an important reason why the uncertainty about the effect that COVID-19 vaccines could have on those who were previously infected with the virus is a critical question that needs to be answered, Siedner said.

“We must remember that many of those who were previously infected are the ones who were in the trenches, on the front line of the epidemic as health workers, grocery store workers, first responders, other key workers and underrepresented minorities in geographic areas without adequate access to health care,” he said.

“The decision to exclude these individuals from a beneficial public health response program should not be taken lightly, as it could only exacerbate many of the health inequalities that the COVID 19 epidemic has only highlighted,” he said.

The answer


The lifespan of coronavirus antibodies is not yet known, but how long a vaccine is effective is also unknown, experts said. The vaccine could protect people for weeks, months or years, but no one knows how long it will fight the virus, said Dr. James Yoon, an infectious disease specialist at New York Presbyterian Hospital.

Once a vaccine is approved and distributed, experts recommend that everyone be vaccinated, starting with high-risk individuals and frontline workers.


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