- Daily coronavirus cases in the United States have decreased by an average of about 74% in the last six weeks.
- Experts hope that the US outbreak has become a corner.
- Economist Ian Shepardson predicted the “effective end of the US COVID crisis” before May.
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As coronavirus vaccinations expanded in the United States earlier this year, encouraging progress was overshadowed by fears of options. Researchers worry that B.1.1.7, the more contagious variant found in the UK, will maintain high levels of coronavirus in the winter, even when more people are taking pictures.
“The restrictions currently in place in the United States are, on average, not strict enough to control B.1
But this week, Shepardson changed his tune: “If the cases of B.1.1.7 do not accelerate significantly next month, it will be realistic to call the effective end of the US crisis COVID – at least in terms of the case and the number of hospitalizations – until the end in April, “Shepardson wrote Monday.
Daily incidence in the United States has decreased by an average of about 74% in the last six weeks. On Monday, the country registered less than 53,000 cases – its lowest daily number since October. On Tuesday, however, daily cases rose to nearly 68,000.
Daily deaths have also fallen by 38% in the last six weeks, while daily hospitalizations have fallen by 55%.
“The balance is more optimistic and less cautious than four weeks ago,” Andrew Neumer, an associate professor of public health at the University of California, Irvine, told Insider.
Such sharp declines in infections and diseases “were not necessarily predicted by people like me,” he added.
Many experts now hope that the US outbreak has become a cornerstone – at least for the next few months.
Why did the cases fall so suddenly?
Scientists do not fully understand why cases have dropped so dramatically in the last six weeks.
Shepardson suggested that B.1.1.7 may not spread as quickly as some epidemiologists fear.
“We still see no signs that the spread of the more infectious variant B.1.1.7 is slowing the decline, even in Florida, where it appears to be most prevalent,” he wrote.
Leana Wen, a visiting professor of health policy and management at George Washington University, told Insider that the main reason is probably that the holidays are behind us.
“The United States was so high before, with the wave of Thanksgiving and Christmas, that we are finally falling out of it,” she said.
Another contributing factor may be that reduced testing means fewer cases are reported: Average daily tests have decreased by 30% in the last six weeks. But this does not explain the significant decline in hospitalizations and deaths.
Weather can also affect the dynamics of coronavirus outbreaks, as some studies have shown that warmer conditions can slow the transmission of coronavirus. But in general, the United States did not notice drastic temperature changes from January to February.
“It’s probably a combination of things – a combination of enough people who are already infected and people who are being vaccinated, so there is some level of protection,” Wen said.
According to some experts, this combination of natural and vaccine immunity may even bring the United States closer to the herd’s immunity threshold.
Is herd immunity closer than we imagine?
Most scientists do not believe that the United States has reached herd immunity – the threshold above which the virus can no longer easily spread from person to person. But several experts believe we can be close.
Dr Martin Macari, a professor of surgery at Johns Hopkins School of Medicine, wrote in The Wall Street Journal last week that “the steady and rapid decline in everyday cases from January 8 can only be explained by natural immunity.”
Based on this, he predicts that COVID-19 will be “mostly extinct” by April.
Shepardson also suggested on Monday that herd immunity “would not be far off” until April.
Scientists calculate herd immunity based on the reproductive value of the virus: the average number of people a sick person infects. Typically, researchers estimate that the reproductive value of the coronavirus – the original virus, not a variant – is between 2 and 3 without intervention such as vaccines or public health measures.
This means that about 50% to 67% of the US population will need to have some immunity – whether through vaccination or natural infection – to achieve immunity to the herd.
However, studies show that B.1.1.7 can increase the reproductive value of the virus by 0.4 to 0.9. In this case, the herd immunity threshold would be higher: up to 75% of the US population is likely to have to develop immunity.
“I don’t think there’s a chance we can get 80% of Americans vaccinated by July, so we won’t reach herd immunity by then,” Wen said.
She added, however, that the United States is likely to see a “significant drop” in infections by May and a subsequent similar drop in deaths.
This period of lower levels of infection, Wen said, “is our ability to get as much immunity as possible in the community” through vaccines.
Shepardson expects that as the United States moves closer to herd immunity, more businesses will reopen.
“The gradual opening of the ongoing services sector will accelerate over the next two months,” he said, “and most of the economy will be open long enough for Remembrance Day.”
Andrew Dunn contributed to the reporting.