Molnupiravir as post-exposure prophylaxis against COVID-19

The virus SARS-CoV-2, which causes COVID-19, is highly transmissible, especially the variant called Delta. This variant is common in Canada, the U.S., Europe and other parts of the world.

People who have been in close contact with someone who has recently been diagnosed with SARS-CoV-2 infection, such as people living in the same household, are at high risk for also becoming infected with SARS-CoV-2.

Preventing infection and illness after exposure

Taking medicine to prevent an infection (and subsequent illness) after exposure to a virus is called post-exposure prophylaxis (PEP).

The pharmaceutical company Merck is conducting a randomized, placebo-controlled trial of molnupiravir (Lagevrio, MK-4482) called Move-Ahead. This study will recruit adults who are living in the same household as someone diagnosed with SARS-CoV-2 infection. Participants are expected to have at least one sign or symptom of COVID-19 but not for more than five days. Molnupiravir will be given at a dose of 800 mg every 12 hours for five consecutive days. Placebo pills will be taken at the same schedule.

The Move-Ahead Study plans to recruit about 1,300 people and will take place in many countries and regions, including Latin America, France, Japan, South Africa, Spain, Turkey and the U.S.

Hopefully, results from this study will become available later in 2021 or in early 2022.

—Sean R. Hosein


Merck. Merck and Ridgeback Biotherapeutics announce initiation of pivotal phase 3 Move-Ahead Study evaluating molnupiravir for post-exposure prophylaxis of COVID-19 infection. Press release. 1 September 2021.