A nurse preparing vaccine doses at a medical office in Los Angeles this month.Credit.Allison Zaucha for The New York Times
Scientists have long said that giving people a single course of a Covid-19 vaccine might not be sufficient in the long term, and that booster shots and even annual vaccinations might prove necessary.
In recent days, that proposition has begun to sound less hypothetical.
Vaccine makers are getting a jump-start on possible new rounds of shots, although they sound more certain of the need for boosters than independent scientists have.
Pfizer’s chief executive said on Thursday that a third dose of the company’s Covid-19 vaccine would “likely” be needed within a year of the initial two-dose inoculation followed by annual vaccinations.
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