A trial of an experimental coronavirus vaccine detected the most sobering signal yet that people who have recovered from infections are not completely protected against a variant that originated in South Africa and is spreading rapidly, preliminary data presented this week suggests.
The finding, though far from conclusive, has potential implications for how the pandemic will be brought under control, underscoring the critical role of vaccination, including for people who have already recovered from infections. Reaching herd immunity — the threshold when enough people achieve protection and the virus can’t seed new outbreaks — will depend on a mass vaccination campaign that has been constrained by limited supply.
Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, noted that it appears a vaccine is better than natural infection in protecting people, calling it “a big, strong plug to get vaccinated” and a reality check for people who may have assumed that because they have already been infected, they are immune.
In the vaccine trial’s placebo group, people with prior coronavirus infections appeared just as likely to get sick as people without them, meaning they weren’t fully protected against the B. 1.351 variant that has swiftly become dominant in South Africa. The variant has been detected only a handful of times in the United States, including a case reported Friday in Virginia, which became the third state to identify the presence of the virus variant.
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