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Next Winter May Be Rough: Models Predict ‘Considerable Surge’

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It’s likely the United States will see another surge of COVID-19 this winter, warned Christopher Murray, MD, director of the Institute for Health Metrics and Evaluation (IHME) at the University of Washington in Seattle.

Speaking at the national conference of State of Reform on April 8, Murray cited the seasonality of the SARS-CoV-2 virus, which wanes in the summer and waxes in the winter. The “optimistic forecast” of IHME, which has modeled the course of the pandemic for the past 13 months, is that daily deaths will rise a bit in the next month, then decline from May through August, he said.

“Summer should be fairly quiet in terms of COVID, if vaccinations rise and people don’t stop wearing masks,” Murray said.

But he added that “a considerable surge will occur over next winter,” because the new variants are more transmissible, and people will likely relax social distancing and mask wearing. The IHME predicts that the percentage of Americans who usually don masks will decline from 73% today to 21% by August 1.

With a rapid decline in mask use and a rise in mobility, there will still be more than 1000 deaths each day by July 1, Murray said. In a forecast released the day after Murray spoke, the IHME predicted that by August 1, there will be a total of 618,523 US deaths from COVID-19. Deaths could be as high as 696,651 if mobility among the vaccinated returns to pre-pandemic levels, the institute forecasts.

Based on cell phone data, Murray said, the amount of mobility in the United States has already risen to the level of March 2020, when the pandemic was just getting underway.

Decreased Infections

If there’s one piece of good news in the latest IHME report, it’s that the estimated number of people infected (including those not tested) will drop from 111,581 today to a projected 17,502 on August 1. But in a worst-case scenario, with sharply higher mobility among vaccinated people, the case count on that date would only fall to 73,842.

The SARS-CoV-2 variants are another factor of concern. Murray distinguished between variants like the one first identified in the UK (B.1.1.7) and other “escape variants.”

B.1.1.7, which is now the dominant strain in the US, increases transmission but doesn’t necessarily escape the immune system or vaccines, he explained.

In contrast, if someone is infected with a variant such as the South African or the Brazilian mutations, he said, a previous COVID-19 infection might not protect the person, and vaccines are less effective against those variants.

Cross-variant immunity may range from 0% to 60% for escape variants, based on the slim amount of data now available, Murray said. In his view, these variants will be the long-term driver of the pandemic in the US, while the UK variant is the short-term driver.

The latest data, he said, show that the Pfizer/BioNTech and Moderna vaccines are 75% effective against the escape variants, with lower efficacy for other vaccines. But booster shots may still be required to protect people against some variants.

Human Factors

Human behavior will also help determine the course of the pandemic, he noted. Vaccine hesitancy, for example, is still high in the US.

By the end of May, he predicted, about 180 million people will have received about two doses of vaccine. After that, he said, “vaccination will flatline due to lack of demand.” The two unknowns are how much campaigns to promote vaccination will increase vaccine confidence, and when children will be vaccinated.

In the US, he said, 69% of adults have been vaccinated or want to get a shot. But that percentage has dropped 5 points since February, and vaccine confidence varies by state.

Murray emphasized that the winter surge he predicts can be blocked if people change their behaviors. These include a rise in vaccine confidence to 80% and continued mask wearing by most people.

However, if vaccine confidence and mask wearing decline, state governments continue to drop social distancing rules, and the uptake of boosters is low, the winter surge could be more serious, he said.

Double Surge

Murray also raised the possibility of a double surge of COVID-19 and influenza this winter. Widely expected last winter, this double surge never materialized here or elsewhere, partly because of mask wearing. But Murray said it could happen this year: History shows that the flu tends to be stronger in years after weak outbreaks.

He advised hospitals to prepare now for whatever might come later this year. Public health authorities, he said, should speed up vaccination, monitor variants closely with additional sequencing, and try to modify behavior in high-risk groups.

Asked to explain the recent surge of COVID-19 cases in Michigan, Murray attributed it partly to the spread of the B.1.1.7 (UK) variant. But he noted that the UK variant has expanded even more widely in some other states that haven’t had an explosive surge like Michigan’s.

Moreover, he noted, Michigan doesn’t have low mask use or high mobility. So the upward spiral of COVID-19 infections there is very concerning, he said.

In regard to the role of children as reservoirs of the virus, Murray pointed out that views on this have changed around the world. For a while, people thought kids didn’t spread COVID-19 very much. That view shifted when UK data showed that child transmission of the B.1.1.7 variant increased by half to 9% of contacts in comparison with the original virus strain.

Dutch data, similarly, showed schools contributing to the latest outbreaks, and some European nations have closed schools. In the US, the trend is to open them.

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