One dose of Pfizer's vaccine may offer strong protection to people who've already had COVID-19, according to two studies published Feb. 25 in The Lancet.
The studies are among the first peer-reviewed papers to explore vaccination practices for COVID-19 survivors, according to The New York Times.
One study conducted by researchers at University College London and Public Health England followed 51 healthcare workers who had routine antibody and COVID-19 testing for 16 weeks starting March 23, 2020. Researchers found one dose of Pfizer's vaccine increased antibody levels 140-fold for 24 workers who had previously experienced mild or asymptomatic COVID-19 infections.
"This increase appears to be at least one order of magnitude greater than reported after
a conventional prime-boost vaccine strategy in previously uninfected individuals," researchers wrote. They suggested giving people blood tests several weeks before they become eligible to receive a vaccine to determine their antibody levels.
Researchers at Imperial College London conducted the second study, which assessed the immune response of 72 healthcare workers who received Pfizer's vaccine between Dec. 23 and Dec. 31, 2020. Researchers took blood samples before workers got vaccinated and 21-25 days after.
Twenty-nine percent of healthcare workers showed evidence of a past COVID-19 infection before they were vaccinated. The vaccine produced "very strong neutralising antibody titres even in those without detectable or very low virus neutralisation titres at baseline," researchers said.
The findings offer additional support for the case of only giving one vaccine to previously infected individuals, which could be an effective way to speed up the vaccine rollout, according to the Times. However, it's still unclear how long this protection may last for previously infected individuals if they only receive one vaccine dose.
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