The effectiveness of vaccinations against new variants would also dictate when, where, and how often additional shots are needed.
Health experts say that at least 70 percent of the country needs to be vaccinated to ensure herd immunity and completely eradicate the epidemic that killed more than 300,000 Americans.
On Friday, only one week after obtaining a federal green light from Pfizer and BioNTech’s COVID-19 vaccine, the Food and Drug Administration officially approved a second emergency vaccine—this one produced by Moderna.
Both the Pfizer vaccine and the Moderna vaccine were developed with new technology that uses messenger RNA.
Covid-19 probably will become as “endemic” as the annual flu virus, under the U.K.’s chief scientific advisor.
Nearly four decades after HIV was discovered, scientists are cautiously optimistic.