British Covid-19 strain could account for 25% to 30% of cases in the United States

But as the authorities are only testing about 4% of the estimated 400,000 weekly cases of Covid-19 in this country, “the current trajectory suggests that the B.1.1.7 variant could now represent up to 25% to 30% of the viruses Americans, ”said Dr. Walensky.

The other variants of Covid-19, first spotted in South Africa and Brazil, have been identified in the United States, but only with a total of around 100 cases, Dr Walensky said.

In his prepared remarks, Dr Walensky said that a collaboration between the CDC and Emory University produced data suggesting that Moderna Inc.

The vaccine produces antibodies capable of neutralizing the British variant, “but having reduced neutralization against the B.1.351 variant”, as the South African strain is known.

It is still unclear how effective current vaccines will actually be against the South African mutation, she said.

Peter Marks, the senior vaccine official at the Food and Drug Administration, said in his prepared remarks that it is not known “how long vaccines will provide protection, and neither are we sure vaccines prevent the transmission of [Covid-19] from one person to another. “

He described how the agency monitors safety among U.S. vaccine recipients, among other steps, analyzing data from millions of people in large health data systems to look for possible safety signals.

The testimony prepared by Dr Marks did not directly address the small number of blood clots in European recipients of the AstraZeneca PLC vaccine, which prompted several European countries to suspend the use of this vaccine. The company said it had not seen any evidence linking the cases to its vaccine. The company has yet to seek FDA clearance, but is expected to do so shortly.

Dr Marks also did not address the issue of the effectiveness of vaccines authorized in the United States in preventing cases of newer variants of Covid-19.

The third witness scheduled for the House subcommittee hearing, Anthony Fauci of the National Institutes of Health, said in scheduled testimony that “so far scientific evidence suggests that Covid-19 vaccines” are permitted for United States “continues to be effective against these variants. “He said his agency continues to research this issue.

Write to Thomas M. Burton at [email protected]