Growing Immunity Driving Drop in COVID Cases? Not So Fast, Experts Say

After more than 3 months of record-breaking surges of COVID-19 cases and deaths in the United States, the national numbers are finally going in a welcome direction: down. Since early January — when the 7-day rolling average of new cases neared 250,000 — the country’s caseload has rapidly dropped by more than two thirds, according to data from the Centers for Disease Control and Prevention (CDC). But public health experts are divided over what’s driving this decline and what explains its speed. Their likeliest explanation: individual behavioral changes. “We’re just seeing such a huge decrease because it was such a huge increase,” says Diane Griffin, MD, PhD, a professor in the Department of Molecular Microbiology and Immunology at the John Hopkins School of Public Health, Baltimore, Maryland. The surge, she says, was partly fueled by social activities during the winter