Merck & Co Inc said on Tuesday its COVID-19 pill was not effective at cutting the risk of coronavirus infections in people living with someone infected with the virus.

The results were similar to data from rival Pfizer Inc , whose COVID pill Paxlovid also failed to prevent infections among household contacts.

The two antiviral drugs are approved as treatments for individuals at risk of severe disease, but enthusiasm for the Merck pill has waned since it was shown to be only 30% effective versus 90% for Pfizer's Paxlovid.

Merck's late-stage trial enrolled over 1,500 participants, who were household contacts exposed to an individual with at least one symptom and had recently tested positive for COVID-19. Its Lagevrio pill, also known as molnupiravir, was given every 12 hours for five days and was compared with a placebo group.

Participants treated with the pill were 23.6% less likely to develop COVID than those given a placebo through day 14, failing to meet the main goal of the trial, Merck said.

Pfizer's Paxlovid and Merck's Lagevrio pills were given emergency use authorization in Dec. 2021 for patients with mild-to-moderate COVID that tested positive for the virus, and who were at risk of progressing to severe COVID. Earlier in February, the U.S. Food and Drug Administration removed the need for a positive test for Merck and Pfizer's treatments in a bid to increase access to the drugs.