- Daily cases of coronavirus in the US have fallen by about 74%, on average, in the past six weeks.
- Experts are hopeful that the outbreak in the US has changed.
- Economist Ian Shepherdson predicted the “effective end of the COVID crisis in America” before May.
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As coronavirus vaccines increased in the US earlier this year, the hopeful progress was overshadowed by fears of variants. Scientists were concerned that B.1.1.7, the most contagious variant discovered in the UK, would keep coronavirus cases high through the winter even as more people were getting vaccinated.
“The restrictions applied in the United States at this time, on average, are not strict enough to control B.1.1.7,” wrote Ian Shepherdson, chief economist at Pantheon Macroeconomics, on February 12. He added that the United States was “in a race between B.1.1.7 and the vaccination rate.”
But this week, Shepherdson changed his mind: “If B.1.1.7 cases do not noticeably accelerate over the next month, it will be realistic to call an effective end to the US COVID crisis, at least in terms of the case and hospitalization numbers, by the end of April, “Shepherdson wrote Monday.
Daily cases in the US have dropped about 74%, on average, in the past six weeks. The country registered fewer than 53,000 cases on Monday, its lowest daily count since October. On Tuesday, however, daily cases rose to nearly 68,000.
Daily deaths have also decreased 38% over the past six weeks, while daily hospitalizations have decreased 55%.
“The balance is more optimistic and less cautious than four weeks ago,” Andrew Noymer, associate professor of public health at the University of California, Irvine, told Insider.
Such drastic declines in infections and diseases “were not necessarily predicted by people like me,” he added.
Many experts are now hopeful that the outbreak in the US has changed, at least for the next several months.
Why have the cases dropped so suddenly?
Scientists don’t fully understand why cases have dropped so dramatically in the past six weeks.
Shepherdson suggested that B.1.1.7 might not be spreading as rapidly as some epidemiologists feared.
“We do not yet see signs that the spread of the more infectious variant B.1.1.7 is slowing the rate of decline, even in Florida, where it appears to be more prevalent,” he wrote.
Leana Wen, a visiting professor of health policy and management at George Washington University, told Insider that the main reason the holidays are likely to be behind us.
The United States was “so high before, with the rise of Thanksgiving and Christmas, that we are finally leaving it,” he said.
Another contributing factor could be that declining testing means fewer cases are being recorded – average daily testing has dropped 30% in the last six weeks. But that doesn’t explain the considerable drop in hospitalizations and deaths.
Weather can also influence the dynamics of coronavirus outbreaks, as some studies have shown that warmer conditions could slow down the transmission of the coronavirus. But overall, the United States did not see drastic temperature changes from January to February.
“It’s probably a combination of things: a combination of there are enough people who are already infected and people who get vaccinated, so there is some level of protection,” Wen said.
Some experts think that combination of natural and vaccine-derived immunity may even bring the US closer to a threshold for herd immunity.
Is herd immunity closer than we think?
Most scientists do not believe that the US has reached herd immunity, the threshold beyond which the virus can no longer easily spread from person to person. But some experts believe we could be close.
Dr. Martin Makary, professor of surgery at Johns Hopkins School of Medicine, wrote in The Wall Street Journal last week that “the steady and rapid decline in daily cases since January 8 can only be explained by natural immunity.” .
Based on that, he predicted that COVID-19 would “almost disappear” in April.
Shepherdson similarly suggested Monday that herd immunity “won’t be far off” in April.
Scientists calculate herd immunity based on the reproductive value of a virus – the number of people a sick person infects, on average. Researchers generally estimate that the reproductive value of the coronavirus, the parent virus, not a variant, is between 2 and 3 without interventions such as 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 herd immunity.
But studies suggest that B.1.1.7 can increase the reproductive value of the virus from 0.4 to 0.9. In that case, the threshold for herd immunity would be higher: up to 75% of the US population would probably need to develop immunity.
“I don’t think there is any chance that we can vaccinate 80% of Americans in July, so we are not going to achieve herd immunity at that time,” Wen said.
However, he added that the United States will likely see a “substantial decline” in infections by May, and a similar decline in hospitalizations in deaths to follow.
This period of lower infection rates, Wen said, “is our chance to get the highest possible immunity in the community” through vaccines.
Shepherdson hopes that as the United States moves closer to herd immunity, more companies will reopen.
“The gradual reopening of the service sector now underway will accelerate over the next two months,” he said, “with most of the open economy in plenty of time for Memorial Day.”
Andrew Dunn contributed reporting.