Covid Vaccines May Need Adjusting to New Strains, Scientists Say

Covid-19 vaccines will have to be adjusted to improve their protective power against mutations such as the one that’s now prevalent in South Africa, researchers said.

A study into a vaccine from Novavax Inc. published Thursday showed that vaccines may be somewhat less effective against new variants. Johnson & Johnson released similar results on Friday from its trial.

While the Novavax vaccine was 89.3% effective in preventing symptomatic Covid-19 among 15,000 volunteers in the U.K., a trial of 4,400 people in South Africa showed that the vaccine was 60% effective in those who were HIV negative and for those who ...