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Inadequate immune responses force Merck to abandon COVID-19 vaccines

Merck, one of the world's most storied vaccine makers, is abandoning the development of its two COVID-19 vaccines after initial trials resulted in inadequate immune responses, Stat News reports. Both vaccines produced lower levels of coronavirus antibodies than have been found in the blood of individuals who recovered from natural COVID-19 infections. For reference, the Pfizer-BioNTech and Moderna vaccines produced antibody levels several times higher than natural infections.

The unsuccessful trials are disappointing in large part because both Merck vaccines would have required just one dose, writes Stat. One of the candidates, which uses the same virus as the one in Merck's successful Ebola vaccine, was being developed in partnership with the International AIDS Vaccine Initiative, which has said it will try to determine if using an oral or intranasal administration route will work better than the current intramuscular injection. It's unclear if Merck will continue to collaborate — IAVI's president Mark Feinberg told Stat he hopes they do — because the pharmaceutical company has suggested it will now turn its focus to developing COVID-19 therapeutics.

As Stat notes, the results show just how difficult vaccine development can be, especially in such a short amount of time, making the rapid success of the Pfizer-BioNTech and Moderna shots seem all the more remarkable. Read more at Stat News.