- The daily number of coronavirus cases in the US has decreased on average by about 74% in the past six weeks.
- Experts are hopeful that the US outbreak has turned a corner.
- Economist Ian Shepherdson predicted the “effective end of the US COVID crisis” before May.
- Visit Insider’s Business section for more stories.
As coronavirus vaccinations increased in the US at the beginning of this year, hopeful progress was overshadowed by fears of variants. Scientists were concerned that B.1.1.7, the more contagious variant discovered in the UK, would keep coronavirus cases high all winter, even if more people got an injection.
“The restrictions currently in place in the US are on average not tight enough to control B.1.1.7,” wrote Ian Shepherdson, chief economist at Pantheon Macroeconomics, Feb. 12. He added that the US was “in a race”. between B.1.1.7 and the rate of vaccinations. “
But this week, Shepherdson changed his voice: “If B.1.1.7 cases don’t accelerate significantly over the next month, it becomes realistic to call the effective end of the US COVID crisis – at least in terms of the case and number of hospital admissions – against. in late April, ‘Shepherdson wrote Monday.
Daily cases in the US have declined an average of about 74% in the past six weeks. The country registered fewer than 53,000 cases on Monday – the lowest daily number since October. On Tuesday, however, the number of daily cases rose to nearly 68,000.
Daily mortality has also decreased by 38% over the past six weeks, while daily hospital admissions have decreased by 55%.
“The balance is more optimism and less cautious than four weeks ago,” Andrew Noymer, 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 are now hoping that the US outbreak has turned a corner – at least for the next few months.
Why have things gone down so suddenly?
Diners will be seated outside at a restaurant in Alexandria, Virginia on May 29, 2020.
REUTERS / Kevin Lamarque
Scientists don’t quite understand why cases have declined so dramatically in the past six weeks.
Shepherdson suggested that B.1.1.7 may not be spreading as quickly as some epidemiologists feared.
“We don’t see any signs yet that the spread of the more contagious B.1.1.7 variety is slowing decline, even in Florida, where it is most common,” he wrote.
Leana Wen, a visiting professor of health policy and management at George Washington University, told Insider that the main reason is likely that the vacation is behind us.
The US was “so high before, with the Thanksgiving and Christmas boom, that we’re finally dropping it off,” she said.
Another contributing factor could be that reduced tests mean fewer cases are recorded: Average daily tests have dropped by 30% over the past six weeks. But that doesn’t explain the significant decline in hospital admissions and deaths.
The weather can also influence the dynamics of coronavirus outbreaks as some studies have shown that warmer conditions can slow coronavirus transmission. But overall, the US did not see any dramatic 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.
That combination of natural and vaccine-derived immunity, some experts believe, may even move the US closer to a herd immunity threshold.
Is herd immunity closer than we realize?
Alameda County employees line up to receive coronavirus vaccines outside St. Rose Hospital in Hayward, California on Jan. 8, 2021.
Jessica Christian / The San Francisco Chronicle / Getty Images
Most scientists don’t believe the US has reached herd immunity – the threshold above which the virus can no longer spread easily from person to person. But a few experts think we can be close.
Dr. Martin Makary, a professor of surgery at Johns Hopkins School of Medicine, wrote in The Wall Street Journal last week that “the constant and rapid decline in the number of daily cases since January 8 can only be explained by natural immunity.”
On that basis, he predicted that COVID-19 would be “mostly gone” by April.
Shepherdson similarly suggested Monday that the herd’s immunity by April “won’t be far off.”
Scientists calculate the herd’s immunity based on the reproductive value of a virus: the number of people infected by a sick person on average. Researchers generally estimate the reproductive value of the coronavirus – the parent virus, not a variant – between 2 and 3 without the intervention of vaccines or public health measures.
That means that about 50% to 67% of the US population would need to have some immunity – either through vaccination or natural infection – to achieve immunity to the herd.
But studies suggest that B.1.1.7 can increase the reproductive value of the virus by 0.4 to 0.9. In that case, the threshold for occupational immunity would be higher: up to 75% of the US population would likely need to develop immunity.
“I don’t think there’s a chance we’ll be able to vaccinate 80% of Americans by July, so we’re not going to achieve herd immunity by then,” Wen said.
However, she added that the US is likely to see a “substantial drop” in infections in May, and a similar drop in hospital admissions to follow.
This period of lower infection rates, Wen said, “is our chance to get as much immunity in the community as possible” through vaccines.
Shepherdson expects that as the US approaches herd immunity, more companies will reopen.
“The gradual reopening of the services sector now underway will accelerate over the next two months,” he said, “while most of the economy is open well in time for Memorial Day.”
Andrew Dunn contributed to the reporting.