(Bloomberg) – Covid-19 cases and hospitalizations are dropping dramatically in the U.S., suggesting that measures to stop transmission are working, at least for now.
More than 27.7 million Americans have tested positive among at least 83 million who are believed to have been infected. An increasing number – 11.8% of the population – have already received at least one dose of a vaccine. And the data collected from cell phones suggests that people are being more cautious in their day-to-day activities. If cases continue to fall, it could buy time for the United States’ vaccination effort to be implemented in the hot summer months ahead, potentially sustaining a long-awaited economic recovery.
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Residents visit a Sutter Health Covid-19 vaccination site
A syringe is filled with a dose of the Pfizer Inc.-BioNTech SE Covid-19 vaccine in Sacramento, California,
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Health experts, for their part, are anticipating challenges. Inoculations need to overcome the highly contagious variants in the UK and South Africa that are now in the United States. And the upcoming holidays – spring break, Easter and Mother’s Day included – pose the threat of group meetings that can quickly increase the spread of the virus.
“The history of outbreaks is that they subside,” said Robert Wachter, head of the department of medicine at the University of California-San Francisco. “They usually come from some combination of changes in behavior, changes in government policy and the impact of immunity.”
Infectious disease experts agree that it is too early to end the pandemic. The declines follow an increase linked to the Thanksgiving and Christmas holidays, and infection levels remain roughly on par with last fall’s trends in about 91,000 new cases confirmed daily.
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New virus cases in the United States decline as vaccination effort takes off
Rochelle Walensky, head of the US Centers for Disease Control and Prevention, sounded a warning signal on Sunday. “We are not out of the woods,” she said on CBS’s “Face the Nation” program, adding that “now is the time to reduce” mitigation efforts.
If these efforts are relaxed “with increasingly transmissible variants out there,” she said, “we could be in a much more difficult situation.”
Walensky’s warning comes as some states, including Iowa and Montana, ease demands on the use of masks and the CDC emphasizes that suppressing community dissemination is the key to reopening schools safely – a priority of the Biden government.
At first, the country experienced regional peaks in the northeast last spring, states of the Sun Belt in the summer and states in the midwest and west during the fall. However, the latest increase worsened almost everywhere in January, producing the deadliest month so far.
Deadly silence
Since then, the numbers have stabilized or decreased. Ali Mokdad, professor of health metrics at the University of Washington’s Institute of Health Metrics and Health Assessment, said that after the holiday boom, Americans began to behave much more cautiously.
“If you look at our data, the week after Thanksgiving, the week after Christmas, it was deadly silence,” said Mokdad. “People stayed at home, even cell phone calls declined.”
The country is still far from herd immunity, a time when the country has so much protection against the dominant strain that it can no longer spread effectively. This will likely require 70% to 85% of the 330 million Americans to be vaccinated or have natural protection, experts say.
At the current vaccination rate, sufficient doses will have been administered by spring break in mid-March to cover about 15% of the U.S. population with two doses, according to Bloomberg’s vaccine tracker. On Easter Sunday, this will increase to around 20% and on Mother’s Day, enough injections can be administered to cover about 30% of Americans.
These estimates are based on last week’s vaccination rates and are likely to increase substantially as more vaccine supplies become available. On Tuesday, the vaccination rate in the US was 1.7 million doses per day, on average.
At this rate, it is estimated that it will take 8 months to cover 75% of the population with a two-dose vaccine.
United Kingdom variant
Meanwhile, the UK’s highly contagious variant, known to scientists as B.1.1.7, is already linked to about 1% to 4% of infections in the United States and is expected to become the dominant strain in late March or April. , according to Gregory Armstrong, director of the CDC’s Advanced Molecular Detection Program.
This could create a race between the spread of the vaccine, which is likely to increase, and the ability of the virus to spread among Americans who are not yet immunized, some experts say.
Armstrong emphasized in an interview that the mutation today remains at relatively low levels. Even if the UK variant – believed to be 50% more transmissible – accounted for 10% of all known infections, it would increase cases by only 5%, according to Armstrong.
This is “small enough that we can’t even detect it,” said Armstrong.
Still, as the variant becomes more prevalent, adherence to measures such as wearing a mask, social distance and vaccination will have to be even better to prevent an increase in infections, he added.
California Mutation
Researchers at Cedars-Sinai recently claimed to have found a US variant in California linked to the Los Angeles holiday season. This discovery has generated new concern about the role played so far by the new mutations.
“There is still no consensus on what to think of it,” said Armstrong. “In the United States, what happened in the last few months, that peak that peaked in early January, a lot of people looked at it and saw nothing in the virus itself that could explain it.”
In contrast, B.1.1.7 already accounted for about 80% of cases in parts of the UK by the time the first concerns were raised about him, said Armstrong.
The United States, however, lags behind many other countries, including the United Kingdom, in its genomic surveillance, in which scientists use genetic data to track the spread of different strains of a disease.
Back pressure
In the short term, new dominant variants can be expected to exert pressure on the forces that are reducing cases. Meanwhile, holiday seasons and major events that traditionally bring people together often coincide with outbreaks of cases.
A series of new events and holidays – from the recent Super Bowl and the Chinese New Year to Mardi Gras, St. Patrick’s Day and then Easter and Easter in April – are expected to test social distancing commitments in the future.
“Which one wins and whether we have a fourth wave is kind of a big unknown right now,” said Wachter of the University of California-San Francisco.
Last year’s Mardi Gras festival dramatically accelerated broadcasting in Louisiana, leading to secondary localized epidemics across the South, according to a pre-printed by scholars from The Scripps Research Institute and Tulane University.
Eventually, Covid-19 can reach an endemic state and become seasonal like other coronaviruses, the common cold and the flu, said Brian Fisher, a senior scholar at the Penn Center for Clinical Epidemiology and Biostatistics. The endemic state has yet to be treated with vaccines, he said, including updated ones.
“Now, how we get there is up for debate and there are likely to be some periods of increased transmission ahead,” he said.
(Updates with daily data on infections, vaccinations)
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