Merck Shuts Down Covid Vaccine Program After Lackluster Data (3)

Merck & Co. is discontinuing development of its two experimental Covid-19 vaccines after early trial data showed they failed to generate immune responses comparable to a natural infection or existing vaccines.

The U.S. drug giant, which has a history of successfully developing vaccines, had adopted a different strategy from rivals Pfizer Inc., Moderna Inc. and Johnson & Johnson, using a more traditional approach of focusing on shots based on weakened viruses. One, called V590, borrowed technology from Merck’s Ebola inoculation, while the other, V591, is based on a measles vaccine used in Europe.

Both were laggards in the...