Impact Series

New COVID-19 prediction fashions forecast a possible fourth wave — and learn how to decrease it

In a bootcamp that launched in January, University of Washington School of Nursing students train other UW students and faculty who hope to help in COVID-19 vaccinations. (Kiyomi Taguchi / University of Washington Photo)

Let’s start with the good news. The number of new COVID-19 cases in the greater Seattle area, Washington state and the national level have all been declining since early January, showing a recovery from what’s known as the third wave of infections.

The potentially bad news? New models predict that a fourth wave could be on the horizon — but if, when and how it crests is uncertain.

We’re in a race against time, health officials warn, pitting our ability to quickly vaccinate as many people as possible against the emergence of more infectious and possibly more deadly variants of the COVID virus. They include strains from the United Kingdom, South Africa and Brazil.

“I’m yo-yoing between pessimism and optimism on a daily basis. I do think that there is a window where the worst of this is behind us, but there are too many open variables to be sure of it,” said Dr. Joshua Schiffer, an infectious disease modeler at the Fred Hutchinson Cancer Research Center.

Depending on how the different factors play out, between 28-to-40% of the King County population will have been infected by the virus by the end of the year, according to a study from Schiffer and colleagues that posted Wednesday on medRxiv. That’s including verified cases and those that go undetected. (The scientists estimate that roughly 15% of the county, which includes tech hubs of Seattle, Bellevue and Redmond, have been infected to date; the official number of confirmed cases is less than 4%.)

Authors of new research modeling COVID infections in King County, clockwise from top left: Joshua Schiffer, Daniel Reeves, Chloe Bracis, Dobromir Dimitrov, Mia Moore, David Swan.

Fred Hutch researchers ran 3,888 simulations in which they altered vaccination rates, vaccine effectiveness in preventing infection and transmission, and what level of infections would trigger the government to enforce a partial lockdown of business and social interactions. They wanted to know which measures matter most in controlling the virus.

Their conclusion: “under all plausible scenarios, rapid vaccination and early enforcement of partial lockdown are the two most critical variables to save the greatest number of lives.”

The research has not yet been peer-reviewed.

Washington so far has given more than 728,000 vaccinations. The state is averaging 28,000 doses administered per day, with a goal of 45,000. About 8% of the population has received one shot, and almost 2% are fully vaccinated. On Monday, eight Washington counties, including King and other populous Puget Sound area counties, were permitted by the state to ease their partial lockdowns.

Modeling from Fred Hutch researchers shows that vaccinating in King County at a rate of 8,000 doses a day, which is approximately Gov. Jay Inslee’s goal, will curb overall infections and death, even with more transmissible variants. In a counterintuitive twist, a medium rate of vaccination gave slightly better outcomes in some scenarios with a much more infectious variant due to when a partial lockdown is triggered. (Fred Hutch Image) Click to enlarge.

Late last week, the Institute for Health Metrics and Evaluation (IHME) shared its updated COVID projections that run through the end of April. The IHME, a research center at the University of Washington, makes predictions at the global, national and state levels.

Here’s what the two organizations forecast:

  • Using numbers most closely matching the current vaccination rate in King County, the Fred Hutch model predicts a fourth wave of cases — caused mostly by the UK variant, known as B.1.1.7 — to hit between May and August, triggering the need for a partial lockdown.
  • If the region is able to reach vaccination numbers closer to 45,000 a week (or 45,000 a day statewide), the fourth wave could possibly be eliminated, or delayed until fall and greatly reduced, depending on multiple factors.
  • IHME predicts that infection and death rates will continue declining for Washington and U.S. at least through the spring — unless we experience a worst-case scenario in which the variants begin spreading wildly, including among people who are vaccinated.

When it comes to a spring COVID surge, “I don’t think any state will allow this to happen,” said Ali Mokdad, an IHME professor and chief strategy officer for Population Health at the UW.

If the downward trends in infections and deaths started reversing, lockdowns would quickly follow, Mokdad predicted. “[States] will go and hit the brakes as fast as they can. As soon as we start hearing that the new variant is taking over, that it’s more likely to be transmitted and it’s deadlier, mask wearing will go up.”

Ali Mokdad, IHME professor and chief strategy officer for Population Health at the UW. (UW Photo)

Mokdad had less certainty for fall and winter, which is when the U.S. and Washington saw its biggest wave in case numbers last year. He expects an increase when cold weather sets in, but the severity will depend on what percent of the population has been vaccinated or already infected, which variants are predominant, and how the vaccine performs against them.

Information is still emerging on the variants. B.1.1.7 has been found in multiple cases in the Puget Sound area and is estimated to be roughly 50% more contagious than the original virus. Last week the first cases of the Brazilian variant and the South African strain were found in the U.S.

The currently approved vaccines appear largely effective against B.1.1.7 and the Brazilian variant, but less so against the South African mutation. That said, the vaccines provide a tremendous benefit and the new variant makes vaccinations more urgent, particularly in the Pacific Northwest.

While Washington, Oregon and Hawaii have done a better job than many other states in terms of controlling the spread of COVID, when it comes to reaching herd immunity, that success puts these Western states at a disadvantage — at least temporarily — compared to states where the infections raged.

Eight states including North and South Dakota, Utah, Arizona and Tennessee have all had case totals of more than 10,000 per 100,000 residents, while Washington has tallied slightly more than 4,000 per 100,000. Epidemiologists estimate that the actual number of infections could be four times higher. That means some states are getting close to 50% infection rates, even before vaccinations are added in.

States with fewer total infections “don’t have nearly as many cases contributing to herd community,” Schiffer said. “And so the burden of vaccination is higher.”

A model from the Institute for Health Metrics and Evaluation (IHME) projecting COVID-19 infections under different scenarios that alter the spread of the UK variant, transmission via those who are vaccinated, and mask use. (IHME Image) Click to enlarge.

Here’s more on what the COVID experts are thinking about, and want you to know:

  • Masks are still key: People should consider doubling up on masks indoors or in crowded situations, and doctors, essential workers, teachers and others should have N95 masks.
  • Vaccinated people need to wear masks: Vaccinated people can likely still spread COVID, even if they don’t get sick themselves. The IHME model assumes that half of vaccinated people could transmit the virus.
  • All of the vaccines help: While their efficacy varies, none of the people who received one of the five vaccines in research trials died of COVID (that includes vaccines from Pfizer, Moderna, AstraZeneca, Novavax and Johnson & Johnson). While the South African variant appears to make the vaccines less effective at preventing infections, “there is no evidence yet that it increases deaths among vaccinated people,” according to the New York Times.
  • One dose or two: More research is urgently needed to answer the question of whether it’s better to prioritize giving one dose to more people, given there are benefits from a single shot.
  • Prevention matters: Epidemiologists talk about “R” or the reproductive number, which is how many people each COVID-19 patient will infect. An R above 1 means cases are rising, and below it’s declining. Every small change to R — more masks, less wasted vaccine, fewer super spreader events, etc. — has big impacts.
  • Don’t forget testing: Routinely deploying rapid COVID tests, while more error prone than PCR tests, could curb outbreaks in settings like schools and universities and among in-person workers.
  • We need more genomic testing: The federal government should ask every lab capable of doing genomic sequencing to run COVID samples in order to track variants of concern.

Editor’s note: This story has been updated to correct that the state is averaging 28,000 vaccination doses daily, not weekly.

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