A flurry of new laboratory studies indicate that vaccines, and especially booster shots, may offer protection against the worst outcomes from the fast-spreading omicron coronavirus variant. The highly mutated virus, however, will still cause many breakthrough infections in vaccinated people and in those who have been infected with older versions of the virus, according to the research.

At a World Health Organization meeting on Wednesday, scientists reported on several studies suggesting that T cells in vaccinated people can put up a strong defense against the variant, which could help prevent severe disease, hospitalization and death.

Also on Wednesday, Dr. Anthony Fauci, President Joe Biden’s top medical adviser for the coronavirus response, shared preliminary data from his institute’s analysis of the Moderna vaccine. While two shots produced a negligible antibody response against omicron in the laboratory, the protection shot up after a third dose, he said.