Variants of the coronavirus are increasingly defining the next phase of the pandemic in the United States, taking hold in ever-greater numbers and eliciting pleas for a change in strategy against the outbreak, according to government officials and experts tracking developments.
The highly transmissible B.1.1.7 variant that originated in the United Kingdom now accounts for 27 percent of all cases in this country. It is the most common variant in the United States, Rochelle Walensky, director of the Centers for Disease Control and Prevention, said Wednesday — a development that officials predicted months ago. Two other variants, which took root in South Africa and Brazil and also are more transmissible, are cropping up with increasing frequency in parts of the United States.
The bottom line on all three remains positive. In laboratory tests, vaccines are just as effective against the variant identified in the United Kingdom as they are against the original strain of the virus. And there is only a modest drop-off in their effectiveness against two others.
“These variants emerged because we continued to give the virus more chance to spread,” said David D. Ho, whose lab at Columbia University is leading the research on the P. 1 variant first discovered in Brazil. “The sooner we vaccinate everyone, the faster we will contain the viral spread and reduce the chance for new variants to emerge.”
But the overall picture hides problems in some places. One or more of the variants — which also cause more severe disease than the original version of the virus — are racing through the Northeast and the Midwest. That has prompted officials in some communities to ask for more vaccine than they would receive under the government’s population-based formula. Officials in the Northwest are watching a major outbreak of the P. 1 variant in British Columbia.
“We need more vaccine down here on the Cape, now,” said Bruce G. Murphy, health director for the town of Yarmouth, Mass., on Cape Cod, which has 82 active cases among its population of just more than 23,000.
The town has a sizable Brazilian community; 13 previous and current infections were caused by the P. 1 variant, most likely introduced by travelers, according to tests conducted by the Broad Institute of the Massachusetts Institute of Technology and Harvard University.
Mass-vaccination centers in the Boston area are little help to Yarmouth residents, especially older people who cannot travel, Murphy said.
“If we see 13 [cases], that could be just the tip of the iceberg coming in,” he said.
Michigan also has asked for more vaccine to control an astonishing surge during which its average daily coronavirus caseload rose from 1,503 on March 7 to 7,020 Wednesday, according to CDC data analyzed by The Washington Post.
Asked whether the administration would ever change its strategy, Andy Slavitt, senior adviser to the White House coronavirus response team, said Wednesday that the government already is able to move vaccine supply from other parts of a state to harder-hit areas.
“We are getting the amount of vaccines we think are needed for the population because that’s fundamental,” Slavitt said. “And then we are working on very tactical areas . . . how to maximize that vaccine distribution so we get the things we want: efficiency, health equity and the other goals that we have.”
In addition to those three variants, the CDC considers two in California “variants of concern” and is watching them closely. It is also monitoring a variant found in New York City.
With most of the rest of the world far behind on immunizations, the virus will continue to spread and mutate, every copy with the potential to spark a variation that current vaccines will not be able to control. The odds of that remain low, experts think, but they are not zero.
“I fear there will be one terrible variant that will come out and take us back to square one,” Ho said.
But experts said vaccines can be boosted, and new ones developed, to address any variants that emerge.
As of April 6, there were 16,275 cases of B.1.1.7, 386 of B. 1.351, first discovered in South Africa, and 356 of P. 1 in the United States. Experts think the actual numbers are much larger, but because the U.S. effort to sequence the genomes of the virus lags, it is difficult to know how widespread the variants truly are.
“The landscape is this big explosion of U.K., the worrisome uptick in P. 1 and then other strains as well,” said Daniel Jones, vice chairman of the Division of Molecular Pathology at the Ohio State University Wexner Medical Center. Within a few weeks, he said, there will be enough infections in the United States to gather better data on immune response from people, rather than through tests in a laboratory.
Lab tests usually involve looking at one mutation at a time; the variants circulating can have many, said Stephen Kissler, an immunology expert at the Harvard T.H. Chan School of Public Health.
And “the human immune system is much more complex than we can emulate in a petri dish, so we can only get partial information,” he said.
Found in more than 24 countries and 25 U.S. states, P. 1 is thought to be up to 2.2 times as contagious and 61 percent more infectious than the original form of the virus. In other words, it produces a bigger viral load, which probably makes people sicker.
Some experts have wondered whether competing variants have slowed its spread. Northern California, for example, is dominated by B.1.427/B.1.429 cases, while Southern California has a higher share of B.1.1.7.
“We are seeing different variants in different parts of the country competing to take over populations,” said Benjamin Pinsky, medical director of the Stanford Clinical Virology Lab.