New data showing that two COVID-19 vaccines are far less effective in South Africa than in other places they were tested have heightened fears that the coronavirus is quickly finding ways to elude the world’s most powerful tools to contain it.
The U.S. company Novavax reported this week that although its vaccine was nearly 90% effective in clinical trials conducted in Britain, the figure fell to 49% in South Africa — and that nearly all the infections the company analyzed in South Africa involved the B.1.351 variant that emerged there late last year and has spread to the United States and at least 30 other countries.
Johnson & Johnson announced Friday that its new shot was 72% effective against preventing moderate or severe illness in the United States, compared with 66% in Latin America and 57% in South Africa.
Laboratory tests had suggested that the vaccines authorized in the U.S. — one from Pfizer and BioNTech, the other from Moderna and the National Institutes of Health — trigger a smaller immune response to the South Africa variant.
Now there is evidence from tests in people that some variants are less vulnerable to certain vaccines.
“From an evolutionary biology perspective, this is totally expected and anticipated,” said Dr. Michael Mina, a Harvard epidemiologist. “But it never feels good to be validated on something so scary.”
Researchers once believed it would take several more months, or even years, for the virus to develop resistance to vaccines. They said the speedy evolution is largely a result of the virus’ unchecked spread.
More than 100 million people have been infected worldwide, and each of those infections is an opportunity for the virus to randomly mutate.
A mutation that happens to give the virus an advantage — the ability to resist the body’s natural defenses, for example — can become the basis for a heartier variant.
One early sign that this process was underway was the significant number of people who were contracting the coronavirus a second time. It appeared that the training their immune systems received during the first infection was failing to protect them from new versions of the virus.