Efficacy depends on the details of a trial, such as where it took place. Johnson & Johnson ran trials at three sites: in the United States, Latin America and South Africa. The overall efficacy was lower than that in the United States alone. One reason for that appears to be that the South Africa trial took place after a new variant had swept across that country. Called B.1.351, the variant has mutations that enable it to evade some of the antibodies produced by vaccination. The variant didn’t make the vaccine useless, however. Far from it: In South Africa, Johnson & Johnson’s efficacy was 64 percent.
Efficacy can also change when scientists look at different outcomes. Johnson & Johnson’s vaccine had an 85 percent efficacy rate against severe cases of Covid-19, for example. That’s important to know, because it means that the vaccine will prevent a lot of hospitalizations and deaths.
As Americans anxiously watch variants first identified in the United Kingdom and South Africa spread in the United States, scientists are finding a number of new variants that originated here. More concerning, many of these variants seem to be evolving in the same direction — potentially becoming contagious threats of their own.
In a study posted on Sunday, a team of researchers reported seven growing lineages of the novel coronavirus, spotted in states across the country. All of them have evolved a mutation in the same genetic letter.
“There’s clearly something going on with this mutation,” said Jeremy Kamil, a virologist at Louisiana State University Health Sciences Center Shreveportand a co-author of the new study.
British government scientists are increasingly finding the coronavirus variant first detected in Britain to be linked to a higher risk of death than other versions of the virus, a devastating trend that highlights the serious risks and considerable uncertainties of this new phase of the pandemic.
The scientists said last month that there was a “realistic possibility” that the variant was not only more contagious than others, but also more lethal. Now, they say in a new document that it is “likely” that the variant is linked to an increased risk of hospitalization and death.