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Merck stops development on its COVID-19 vaccine candidates

merck covid vaccine development
Photo via Amy/Flickr (CC BY 2.0)

Though a number of pharmaceutical companies have been successful in creating COVID-19 vaccines, Merck has stopped the development of its two vaccine candidates. 

As NPR reported, Merck reported on Jan. 25 that its two candidates didn’t generate enough of an immune response to effectively protect people against the coronavirus, even though they were deemed safe in trials. 

The article noted that Phase 1 clinical studies for the two vaccine candidates—known as V590 and V591—were, according to Merck’s statement, “generally well-tolerated, but the immune responses were inferior to those seen following natural infection and those reported for other SARS-CoV-2/COVID-19 vaccines.” Both Pfizer’s and Moderna’s vaccines have about a 95% effectiveness.

Though Merck is out of the vaccine development mix, it’s still at work on two therapeutic drugs, including one designed to protect the respiratory system from the effects of COVID-19. That drug already has a commitment from the U.S. government, having purchased 100,000 doses for about $356 million.

“Merck’s announcement in many ways underscores just how extraordinary the success of the Pfizer and Moderna vaccines are,” Dennis Carroll, former head of the pandemic unit at the federal Agency for International Development, told USA Today. “Merck’s announced ‘failure’ comes on the heels of other reports on field trials of the Chinese and Russian vaccines that show modest–at best–efficacy.”

USA Today noted that the “Merck vaccines were different from the others in that they used distinct, harmless viruses to deliver their payload. The International AIDS Vaccine Initiative, which was working with Merck on one of the vaccine candidates, said it remains committed to the vaccine type and hopes to determine whether administering it, perhaps as a nasal spray rather than a shot in the arm, would improve effectiveness.” 

NPR’s report added that Merck’s vaccine development strategy involved a “replicating viral vector” vaccine—different from the messenger RNA approach that Pfizer and Moderna successfully created, and a third company, Sanofi, is developing. While the replicating viral vector method generally takes longer to develop, the resulting vaccine can also give patients a long-lasting immunity using just a single dose. 

Dr. Dean Y. Li, president of Merck Research Laboratories, stated, “We are resolute in our commitment to contribute to the global effort to relieve the burden of this pandemic on patients, health care systems and communities.”

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Sources: NPR, USA Today


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