For most of the pandemic, coronavirus surges followed a now-familiar pattern.
Cases rose first, then a few weeks later, hospitalizations followed. And after a month or so, deaths rose, too.
But during the most recent wave, fueled by the omicron variant of the coronavirus, something changed. Not only were reinfections and breakthrough infections more common than before, the data also showed the death rate bucked the trend.
Infections and hospitalizations soared, yet the number of deaths remained relatively low. At the peak of the delta wave last summer, the death rate was 12% lower than the hospitalization rate. During omicron, it was 20% lower.
A recent Seattle Times analysis of the state’s COVID-19 death data also found that omicron’s surge hit some parts of the state harder than others, including in Southwestern and Eastern Washington, where factors like levels of immunity, weather, behavioral differences and socioeconomic status, among others, could have played a part in transmission.
While deaths did rise during the omicron surge — more than 2,000 Washingtonians died between mid-December and mid-February — they increased at a much slower rate than during the delta wave.
Over the course of the pandemic, and particularly since the introduction of vaccines, the rates of infections, hospitalizations and deaths varied across the state.
In Washington, the state Department of Health grouped counties based on which independent regional organization is working within each community. The Times used these regional classifications to analyze COVID trends.
During the height of the omicron and delta waves, the Cascade Pacific region, which covers Grays Harbor, Mason and Cowlitz counties, recorded the highest case, hospitalization and death rates.
Eastern Washington trends followed. The Better Health Together region, which includes Ferry, Spokane, Stevens, Pend Oreille, Lincoln and Adams counties, and the Greater Columbia region, which includes Yakima, Walla Walla and Garfield counties, were also more affected by the virus during both recent surges.
Though fewer people died in Western Washington during last summer’s delta wave, omicron death rates rose here in January this year, specifically in Grays Harbor, Pacific, Cowlitz, Lewis, Thurston, Mason and Pierce counties.
In addition, DOH data showed higher death rates were generally associated with regions with a greater percent of people who live below the poverty line, which is often linked to high rates of chronic health conditions and restricts access to health care, said DOH spokesperson Emily Fredenberg.
Vaccination rates played a large part in COVID trends during the delta surge.
Eastern Washington counties generally reported vaccination rates of less than 40% at the time. Meanwhile, King County, which had a vaccination rate of about 68.4%, recorded the lowest rates of infection, hospitalization and death.
While community vaccination levels and county public health guidance differ throughout the state and heavily play into transmission, Lacy Fehrenbach, the state’s deputy secretary of COVID-19 response, recently said that many factors — including weather and university and college schedules — can also play a role.
“There’s lower risk to be outdoors,” Fehrenbach said. “That’s partly why with other respiratory viruses there’s a lot of risk in the wintertime. We’re all coming indoors and ventilation is not as good as it is outside.”
In fall 2020, for example, much of the United States also saw increased transmission as students returned to college campuses, she said.
Vaccination levels played an even larger role in hospitalization and death rates during the omicron surge, data shows.
Although King County, for example, had a 77% vaccination rate in mid-December, when omicron was starting to circulate through the region, the county recorded one of the highest case rates during the surge. But hospitalizations remained low.
At the time, breakthrough infections were also making up more than half of new daily cases, according to state data.
On the other side of the state, where less than half the population remained unvaccinated in the Better Health Together and Greater Columbia regions, the death and hospitalization rates ranked highest in the state.
“When we look at the disparities in terms of rates of infections, hospitalizations and deaths specifically, we know we’ve been impacted at a disproportionate rate compared to the rest of the state,” said Lilian Bravo, director of public health partnerships at Yakima County’s public health department — which the state has included in its Greater Columbia region.
Bravo pointed to the county’s workforce as one reason transmission levels have been so high throughout the pandemic. Because the county’s biggest employers are in health care, agriculture, manufacturing and the food industry, fewer people were able to work from home than in the rest of the state, she said.
Yakima County has historically ranked low when comparing counties’ health outcomes and health behaviors in the state, Bravo said, nothing that more people are obese and have diabetes there compared with the state average.
“So specifically looking at COVID comorbidities like obesity, diabetes [and] hypertension, which were more likely to be associated with deaths, many more in our community already live with these conditions so we were already a sicker community coming into the pandemic,” she said.
Dr. Francisco Velazquez, health officer in Spokane County, said his county’s older population likely contributed to higher transmission and hospitalization rates. , compared with 12% in King County, according to DOH data.
Spokane County, like Yakima County, also has a higher percentage of multigenerational households, which could have sped up spread to older family members, he said. A larger Hispanic community — which during the delta wave had the lowest vaccination rate among racial and ethnic groups — and a more conservative population with vaccine concerns also likely contributed, Velazquez said.
“There’s still a lot of work to be done, but it’s not something we’re going to slow down or stop,” he said.
The omicron wave also presented a few anomalies. During its peak, Pierce County and the group including Whatcom, Skagit and Snohomish counties recorded one of the highest death rates, despite a high vaccination rate.
“There are a number of reasons why different waves impact regions differently, and it can be difficult to establish the reason in any one situation,” Fredenberg said. In addition to levels of immunity and behavioral differences between counties — like wearing masks and social distancing — age, travel and commerce, and socioeconomic status can play significant roles in transmission, she said.
Meanwhile, in the region that covers the rural, more sparsely populated Clark, Skamania and Klickitat counties, hospitalization rates remained low despite a notably low vaccination rate.
In that case, the counties’ proximity to Portland might be a factor, said epidemiologists at the state Department of Health.
“Outside of Vancouver, the population is small — there are four hospitals in Vancouver, Clark County, while Skamania and Klickitat counties each have one, small hospital,” DOH said. “The biggest hospitals for the region are in Portland. It is likely people are going there for definitive care,” which would mean they wouldn’t be counted in Washington state’s hospitalization numbers.