Offices are canceling holiday parties. Broadway performances are being shuttered because of breakthrough infections among the casts. College finals are being moved online.
Coronavirus cases are spiking again in New York City, beyond anything seen since last winter, and in much of the United States, where the Delta variant remains by far the dominant version. The country is reporting more than 120,000 new cases per day on average, according to a New York Times database — a 40 percent increase from two weeks ago, and 70 percent more than when cases stopped falling in early November.
While most people who are unvaccinated remain at much higher risk, a combination of factors — widespread transmission, waning immunity and the circulation of highly infectious variants — has led to breakthrough infections among the vaccinated.
Several new laboratory studies indicate that vaccines, and especially boosters, may offer substantial protection against the worst outcomes from the fast-spreading Omicron coronavirus variant. Still, the new variant will infect many people who have been vaccinated or recovered from older versions of the virus, according to the research.