Merck ends development on two potential COVID-19 vaccines after poor results

A sign on a wall has Merck's name and logo.
The corporate headquarters of drugmaker Merck in Kenilworth, N.J.
(Seth Wenig / Associated Press)

Merck is giving up on two potential COVID-19 vaccines following poor results in early-stage studies.

The drugmaker said Monday that it would focus instead on studying two possible treatments for the coronavirus, which also have yet to be approved by regulators. The company said its potential vaccines were well-tolerated by patients, but they generated an inferior immune system response compared with other vaccines.

Merck entered the race to fight COVID-19 later than other top drugmakers.

It said last fall that it had started early-stage research in volunteers on potential vaccines that required only one dose. Vaccines developed by Pfizer and Moderna were already in late-stage research at that point.


The Food and Drug Administration allowed emergency use of both the Pfizer and Moderna vaccines late last year. Each requires two shots.

Five potential vaccines have reached late-stage testing in the U.S., the final phase before a drugmaker seeks approval from regulators. Results from a single-dose candidate developed by Johnson & Johnson are expected soon.

A small lab tries to alter one gene of the coronavirus, hoping that change will offer a way to kill it.

Nov. 13, 2020

Since vaccinations began in December, nearly 22 million doses have been delivered to Americans nationwide, according to the Centers for Disease Control and Prevention. Nearly 6% of the population has received at least one dose.

A total of 3.2 million people, or 1% of the population, have received both doses required for those vaccines.

More than 419,000 people have died in the United States from COVID-19, according to Johns Hopkins University.

The federal government is paying Merck about $356 million to fast-track production of one of its potential COVID-19 treatments under Operation Warp Speed, a push to develop COVID-19 vaccines and treatments. The money will allow Merck, which is based in Kenilworth, N.J., to deliver up to 100,000 doses by June 30 if the FDA clears the treatment for emergency use.


The treatment, known as MK-7110, has the potential to minimize the damaging effects of an overactive immune response to COVID-19. This immune response can complicate the lifesaving efforts of doctors and nurses.