The New York Times, January 25, 2021


Merck announced on Monday that it was abandoning a pair of Covid-19 vaccines in clinical trials.

The news came as a disappointment at a time when the United States and other countries are struggling to accelerate their sluggish vaccination campaigns and new coronavirus variants threaten to bring surges over the next few months.

The two projects are the second and third vaccines to be abandoned in clinical trials. The University of Queensland in Australia abandoned its own effort in December. Sanofi and other vaccine makers have paused some projects after getting disappointing initial results but are now regrouping to move forward.

Merck was slower than other companies to get into the Covid-19 vaccine race. In June, it acquired the Austrian firm Themis Bioscience to develop a vaccine originally designed at Institut Pasteur, based on a weakened measles virus. Researchers began a Phase 1 trial in August. In a second effort, Merck partnered with IAVI, a nonprofit scientific organization that develops vaccines and treatments, on another vaccine. For that one, they used the same design that they successfully employed to make a vaccine for Ebola.

Merck and IAVI were awarded $38 million for their vaccine research, but neither of Merck’s projects earned the lavish support that Operation Warp Speed showered on other efforts from companies such as Moderna and Johnson & Johnson. In its announcement, Merck said that both vaccines looked safe in early clinical trials. But neither produced a strong response from the immune system. They decided that it was not worth going forward with large-scale trials that would demonstrate whether the vaccines protected people from Covid-19.

“We are grateful to our collaborators who worked with us on these vaccine candidates and to the volunteers in the trials,” Dr. Dean Y. Li, the president of Merck Research Laboratories, said in a statement.

Merck will instead focus its Covid-19 efforts on an experimental antiviral drug known as molnupiravir, in partnership with Ridgeback Biotherapeutics. Originally designed for influenza, it has shown promising effects in studies on animals and in early clinical trials. The trial is set to finish by May, although preliminary results could come out as early as March.

IAVI said it would continue searching for Covid-19 vaccines. “Our scientists will continue to evaluate other candidates to see if other routes of administration or changes to the construct could lead to improved immune response,” said Karie Youngdahl, senior director and head of global communications at IAVI.

Copyright 2021 The New York Times Company. Reprinted with permission.