The steady drumbeat of reports about new variants of the coronavirus — first in Britain, then in South Africa, Brazil and the United States — have brought a new worry: Will vaccines protect against these altered versions of the virus?
The answer so far is yes, several experts said in interviews. But two small new studies, posted online Tuesday night, suggest that some variants may pose unexpected challenges to the immune system, even in those who have been vaccinated — a development that most scientists had not anticipated seeing for months, even years.
The findings result from laboratory experiments with blood samples from groups of patients, not observations of the virus spreading in the real world. The studies have not yet been peer-reviewed.
But experts who reviewed the papers agreed that the findings raised two disturbing possibilities. People who had survived mild infections with the coronavirus may still be vulnerable to infection with a new variant; and more worryingly, the vaccines may be less effective against the variants.
Existing vaccines will still prevent serious illness, and people should continue getting them, said Dr. Michel Nussenzweig, an immunologist at Rockefeller University in New York, who led one of the studies: “If your goal is to keep people out of the hospital, then this is going to work just fine.”
But the vaccines may not prevent people from becoming mildly or asymptomatically infected with the variants, he said. “They may not even know that they were infected,” Dr. Nussenzweig added. If the infected can still transmit the virus to others who are not immunized, it will continue to claim lives.
The vaccines work by stimulating the body to produce antibodies against the coronavirus. Scientists had expected that over time, the virus may gain mutations that allow it to evade these antibodies — so-called escape mutations. Some studies had even predicted which mutations would be most advantageous to the virus.
But scientists had hoped that the new vaccines would remain effective for years, on the theory that the coronavirus would be slow to develop new defenses against them. Now some researchers fear the unchecked spread has given the virus nearly unfettered opportunities to reinvent itself, and may have hastened the appearance of escape mutations.
Neither the South African variant nor a similar mutant virus in Brazil has yet been detected in the United States. (The more contagious variant that has blazed through Britain does not contain these mutations and seems to be susceptible to vaccines.)
Fears that the vaccines would be powerless against new variants intensified at a scientific conference held online on Saturday, when South African scientists reported that in laboratory tests, serum samples from 21 of a group of 44 Covid-19 survivors did not destroy the variant circulating in that country.
The samples that were successful against the variant were taken from patients who had been hospitalized. These patients had higher blood levels of so-called neutralizing antibodies — the subset of antibodies needed to disarm the virus and prevent infection — than those who were only mildly ill.
The results “strongly, strongly suggest that several mutations that we see in the South Africa variant are going to have a significant effect on the sensitivity of that virus to neutralization,” said Penny Moore, a virologist at the National Institute for Communicable Diseases in South Africa who led the study.
The second study brought better tidings, at least about vaccines.
In that study, Dr. Nussenzweig and his colleagues tested samples from 14 people who had received the Moderna vaccine and six people who had received the Pfizer-BioNTech vaccine. – New York Times