New Drug Ensitrelvir Shows Promise in Preventing COVID-19 Infection After Exposure

A recent study published in the New England Journal of Medicine reveals that the antiviral drug Ensitrelvir can significantly reduce the risk of COVID-19 infection when administered to individuals exposed to confirmed cases. Unlike vaccines, which many people currently avoid and do not fully prevent infection, Ensitrelvir offers a new preventive approach by targeting the virus's replication process.

Ensitrelvir, approved in Japan for treating COVID-19 symptoms, works by inhibiting a viral enzyme essential for cutting a large protein into functional units, thereby disrupting the virus's ability to replicate. Clinical trials conducted between 2023 and 2024 across the United States, Japan, South Africa, Vietnam, and Argentina involved about 2,000 participants who were exposed to infected household members but initially tested negative and symptom-free.

Participants aged 12 and older, excluding pregnant women, received either Ensitrelvir or a placebo within three days of exposure. Over a 10-day monitoring period, only 2.9% of those treated with Ensitrelvir developed COVID-19, compared to 9% in the placebo group, marking a reduction of over two-thirds in infection risk. Additionally, the drug delayed symptom onset and reduced viral shedding among those who became infected. No significant side effects were reported.

The U.S. Food and Drug Administration approved Ensitrelvir for COVID-19 prevention in early June 2026, although it has yet to be authorized for use in Israel. This development offers a new tool to protect high-risk individuals who are unvaccinated or insufficiently protected by vaccines, potentially changing household management of COVID-19 exposure beyond isolation and mask-wearing.

Summary: A new antiviral pill, Ensitrelvir, effectively prevents COVID-19 infection in people exposed to the virus, reducing infection risk by over two-thirds and delaying symptoms, according to a multinational clinical trial. The drug is FDA-approved in the U.S. but not yet authorized in Israel.