One Vaccine Dose May Protect People Who Had COVID-19

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One Vaccine Dose May Protect People Who Had COVID-19

Only one dose of the approved two-dose regimen for one of the two most common COVID-19 vaccines may be needed in people who have already recovered from the viral infection, according to a new study published in the journal Nature Medicine.

Like most vaccines, the COVID-19 vaccines used in the United States work by training the body’s immune system to produce antibodies — proteins that are specifically targeted toward a substance that the body is trying to attack. In this case, the immune system is trained to target the spike proteins found on the surface of the coronavirus that causes COVID-19. These antibodies can be detected and measured in the blood, which shows how well someone has developed an immune response that is likely to fight off the virus if future exposure occurs.

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For the latest study, researchers looked at a group of 1,090 people who took part in a study of the Pfizer–BioNTech COVID-19 vaccine (which is given in two doses, 21 days apart). All of the study participants were healthcare workers in the Cedars-Sinai Health System in California, and they took a survey after their vaccination that asked about symptoms they experienced after receiving the vaccine, as well as any prior COVID-19, as noted in a Cedars-Sinai press release. Participants also had their antibodies to the coronavirus measured at three different points in time — before or up to three days after the first dose of the vaccine, seven to 21 days after the first dose, and seven to 21 days after the second dose.

Single dose shows protective effects in those who had COVID-19

Based on survey responses, the researchers identified 35 participants who had previously had COVID-19 and had received a single dose of the vaccine at the time of the survey, as well as 228 participants with no history of COVID-19 who had received both doses of the vaccine at that time. They found that both groups had similar levels of coronavirus-specific antibodies, indicating a likely similar level of protection against future COVID-19. Post-vaccine symptoms following the first dose were more pronounced in participants who had previously had COVID-19, which isn’t surprising, since their immune system would be expected to already recognize the virus’s spike proteins and to mount a more robust immune response.

The researchers noted that based on these results, at least some people who already had COVID-19 may only need one dose of a COVID-19 vaccine to achieve the same degree of protection offered by two doses in most people. But there are plenty of unanswered questions, such as how long an antibody response from a single vaccine dose lasts in this group. Larger studies on this topic would be needed, the researchers noted, before any changes to the standard two-dose protocol for the Pfizer vaccine could be made for people with previous COVID-19, and separate studies might be needed to examine whether the other two-dose vaccine, by Moderna, could also be given as a single dose to this group.

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Quinn Phillips

Quinn Phillips

Quinn Phillips on social media

A freelance health writer and editor based in Wisconsin, Phillips has a degree from Harvard University. He is a former Editorial Assistant for Diabetes Self-Management and has years of experience covering diabetes and related health conditions. Phillips writes on a variety of topics, but is especially interested in the intersection of health and public policy.

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