You’ve just seen your favorite rock band in a packed arena — and as the excitement fades, the worry sets in. Was this a “super spreader” event? When was your last booster? In that moment, wouldn’t it be a relief to know you could just take a pill to protect yourself?
A recent study presented at the Conference on Retroviruses and Opportunistic Infections in San Francisco introduces ensitrelvir, an antiviral pill developed by Japanese pharmaceutical company Shionogi, which shows promise in preventing COVID-19 infections among individuals exposed to the virus.
In this study, over 2,300 participants aged 12 and older who were living with someone recently diagnosed with COVID-19 were randomly assigned to receive either ensitrelvir or a placebo for five days. The administration of the medication commenced within three days of their housemate’s symptom onset. Results indicated that approximately 3% of those who took ensitrelvir developed COVID-19, compared to 9% in the placebo group, suggesting that the drug reduced the risk of infection by 67%.
Dr. Frederick Hayden, professor emeritus of medicine at the University of Virginia School of Medicine, who presented the data, remarked in a Time article, “This study is the first where this strategy [to prevent COVID-19] was documented to succeed.”
Ensitrelvir functions by inhibiting the replication of SARS-CoV-2, the virus responsible for COVID-19. It has already been approved in Japan for treating COVID-19, where it has been shown to reduce hospitalizations among high-risk individuals and shorten the duration of symptoms in others. The U.S. Food and Drug Administration is considering the drug for fast-track approval as a preventive measure against COVID-19.
The concept of using antiviral treatments for post-exposure prophylaxis is not new. For instance, oseltamivir (Tamiflu) has effectively prevented influenza among household contacts. However, previous studies with COVID-19 antivirals like Paxlovid and molnupiravir did not demonstrate similar preventive benefits.
This study’s findings highlight the potential of ensitrelvir as a preventive tool against COVID-19, especially for individuals at higher risk of severe disease. Further research and regulatory review will determine its role in future COVID-19 prevention strategies.
