Massachusetts on Wednesday reported striking increases in COVID infections and hospitalizations, with the state reporting that 957 people were hospitalized with the virus, the highest number since mid-February. It also recorded a new high for the fall of 4,838 confirmed coronavirus cases in a single day.
The Thanksgiving holiday likely contributed to some of the uptick, said Dr. David Hamer, a Boston University professor of global health and medicine. “We saw this last year,” Hamer said. “After each holiday there was an increase in cases.”
As the Delta variant continued to sicken thousands, the United States on Wednesday recorded its first confirmed case of the Omicron strain, as scientists around the world raced to understand whether the mutated version of the coronavirus is more dangerous and spreads more quickly.
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The Centers for Disease Control and Prevention said the Omicron case was identified in a California resident who had traveled back from South Africa on Nov. 22, and who had been fully vaccinated. It said the person, who was in quarantine, had mild symptoms that are improving and that all close contacts had been identified and had tested negative.
“We knew it was just a matter of time before the first case of Omicron would be detected in the United States,” said Dr. Anthony Fauci, the country’s top infectious disease expert, in a White House announcement.
The news came with at least 23 other countries now reporting cases of Omicron infections, while conditions in South Africa, which reported among the first known cases last week, have grown ominous. South African authorities reported Wednesday that the country’s new cases of COVID-19 nearly doubled in one day, and that the positivity rate in people tested had soared to 16.5 percent, up from just 1 percent in early November.
Hospitalizations for COVID-19 are also rising in South Africa, but not as dramatically as new cases.
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Early on in the pandemic, the ability of the United States to quickly detect new variants of COVID was widely criticized. But researchers say the nation’s surveillance system has greatly improved, with many more labs on the case and the CDC coordinating their efforts to regularly sequence positive samples to pinpoint variants.
“We do more genomic sequencing for [the coronavirus] than any other country,” said Dr. Jacob Lemieux, an infectious disease specialist at Massachusetts General Hospital and co-leader of the viral variants program at the Massachusetts Consortium on Pathogen Readiness. “That allows us to know that, right now, Omicron is not here at a high level. Perhaps there are a small number of cases and we expect that to grow.”
In an effort to delay the spread of Omicron, the United States is planning to require all air travelers into the country be tested for COVID-19 within one day before boarding their flights, up from the current three days.
Scientists say it will be several more weeks before they know if Omicron is more easily spread than Delta, and whether it produces more serious illness. Teams of researchers are also intensely studying whether Omicron is more resistant to the current vaccines or a previous infection.
With so many unknowns, researchers are urging caution about assuming the worst regarding the surge in COVID cases in South Africa and rising hospitalizations there, too. They say one reason for the worrisome increases may be because so few people in South Africa have received the shots.
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“South Africa is still under-vaccinated, only 30 percent are fully vaccinated, so you have a large percentage of the population that may just be vulnerable,” said Dr. Nahid Bhadelia, founding director of the Boston University Center for Emerging Infectious Diseases Policy and Research.
“The other thing to note is that a more transmissible variant may just increase hospitalizations because it is a function of reaching more people,” she said. “It may not . . . say a lot about the rate of hospitalizations that are occurring in that area.”
Executives at two major COVID vaccine makers have expressed guarded optimism that the current medicines, administered with a booster, would provide at least some measure of protection against Omicron.
The chairman of Moderna Inc. on Tuesday said that studies show a booster shot of his firm’s two-dose regimen substantially increased disease-fighting antibodies in recipients — by as much as tenfold. Meanwhile, the chief executive of BioNTech, which helped develop a similar COVID-19 vaccine in a partnership with Pfizer, said the current generation of shots probably will still protect against severe disease in people infected with the variant.
One of the factors worrying researchers is the high number of mutations — at least 30 — on the spike protein of Omicron, which cover the outside of the virus and is the area where the virus attaches to cells. The protein is also used by the three vaccines available in the United States to induce the body to make protective antibodies against the virus. With so many mutations in this critical protein, the fear is that Omicron may be able to evade the protection.
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“Everyone is sort of pivoting to anticipate that changes will be needed” in the vaccines, said Dr. Jeremy Luban, a scientist at the University of Massachusetts Medical School and co-leader of the the viral variants program at the Massachusetts Consortium on Pathogen Readiness.
Luban said booster shots generate an “extremely high” level of antibodies for fighting off COVID, and it is possible it will be sufficient to fight off Omicron.
“That being said, many of us are speculating that there is going to be a pretty big hit in the magnitude of the protection that those antibodies confer,” he said.
But Luban and other scientists said one other critical part of the immune system, known as T cells, may withstand Omicron and still provide protection.
“We really focused the vaccines on antibody responses and I think the antibodies prevent infection, but in terms of influencing disease course, I think we have not yet fully tapped into T cell responses, which may be really critical, and it’s certainly something that within [the consortium] we are working on,” said Dr. Bruce Walker, director of the Ragon Institute of MGH, MIT, and Harvard and co-leader of the consortium.
“All of the vaccine platforms have been amazing, and they may need to be updated, and there are hardworking, bright people working around the clock on that,” added Lemieux.
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“But it’s also clear that we are in this Whac-A-Mole game of variants and so we need to take a step back and ask whether a pan-variant vaccine is possible,” Lemieux said. “I think it’s a really important scientific endeavor because this isn’t the last variant.”
Material from Globe wire services was used in this report.
Kay Lazar can be reached at kay.lazar@globe.com Follow her @GlobeKayLazar. Felice J. Freyer can be reached at felice.freyer@globe.com. Follow her @felicejfreyer.