Two Covid-19 vaccines stalled by potential side effects have one key feature in common: Both are based on adenoviruses, cold germs that researchers have used in experimental therapies for decades with varying results.
Johnson & Johnson said late Monday it would pause its trial to investigate an illness, which it didn’t specify, in a study participant. Meanwhile, AstraZeneca Plc’s U.S. trial of the vaccine it’s developing with the University of Oxford has been halted by regulators for more than a month after neurological symptoms arose in two volunteers.
With AstraZeneca in a pit stop, vaccines from Moderna Inc. and the Pfizer Inc.-BioNTech SE partnership have taken the lead in the race to be first out with a shot. Meanwhile, the two paused trials are reviving questions about adenoviral vectors, which have been used in laboratory, animal and human experiments for years. In some cases, the experiments have succeeded, but not always.
And this year, with Covid-19 vaccines entering strongly into the politics of the hour, transparency and trust are key to fighting a virus that’s hit more than 39 million people globally and hamstrung economies. If concerns about side effects in experimental vaccines in trials using adenoviruses are validated, it could boost skepticism in the general public and raise questions for other drugmakers.