Why Washington state is seeing a 4th COVID-19 wave

Even as COVID-19 vaccines are rolled out throughout the U.S., Washington state is reeling from a fourth wave of infections, with hospitalizations surging for people age 40 to 59 -- and among many much younger.

Virus cases and hospitalizations have steadily risen since March, and Gov. Jay Inslee announced last week the state had entered its fourth wave. Earlier in April, he'd rolled back three counties to Phase 2 of reopening restrictions.

Currently, 40-to-59-year-olds account for the highest number of patients in hospitals, followed by 20-to-39-year-olds, according to state data showing COVID-like-illness hospitalizations, which don't rely on a diagnosis but monitor overall trends.

Ryan Erlewine, director of pharmacy and clinical support services at Legacy Salmon Creek Medical Center in Vancouver, Washington, told ABC News that people with "pandemic fatigue" who haven't gotten vaccinated may be contributing to this rise.

"The bulk of those folks that are 40-to-59 that are being hospitalized, most of them are not vaccinated," he said.

"We're about half of what we were at our highest [hospitalization] levels when we had the highest back in December," he said. "Locally, we have seen a large increase in cases over the last week. ... So that is the worry -- we're maybe seven to 14 days out from our peak, unfortunately, based off the increasing case totals we've seen in the community."

More than 600 virus hospitalizations have been reported from Washington state's 44 hospitals -- the most in months, Fox affiliate KCPQ reported last week.

The state reported 483 hospitalized patients with COVID-like illness and a hospitalization rate of 7% on April 25. While a major decline from the December peak of 13%, it's still a rise from the 4.2% rate from February.

Dr. Amy Compton Phillips, CEO of the Providence Hospital System, said the system's 26 hospitals in the Pacific Northwest have seen a worrisome spike in caseloads.

"What we're seeing is a little bit scary," she told ABC affiliate KOMO. "We had about 500 more people this April in our hospitals across our footprint than we had last April, so we're actually seeing more cases now than we were last April when the whole world was shut down."

At a recent press briefing, Seattle King County Public Health Officer Dr. Jeff Duchin said there's a surge of people in their 20s being hospitalized with COVID-19 compared with those in their 70s.

"We don't yet have enough younger adults vaccinated to counteract the increased ease with which the variants spread," Duchin told NPR.

Erlewine said that young, unvaccinated people attending gatherings has played a role in the most recent surge.

In Washington, those 16 and older became eligible for the vaccine on April 15. So far, just 6% of 16-to-17-year-olds, 22% of 18-to-34-year-olds and 32% of 35-to-49-year-olds are fully vaccinated, according to state data.

Erlewine is urging young people to get the vaccine to protect their community.

"Younger people in general think they're a little bit more invisible," he said. "I think it's hard for younger people to understand that you're just not providing yourself with immunity, you're preventing others from getting it from you as well. We really need to flip the script a bit and think of it more as being a little bit selfless. We're doing something for the greater good."

Inslee on Tuesday offered an optimistic message, announcing a "two-week pause" on deciding whether additional counties would phase down.

"If people remain committed to this," Inslee said, "there's a reason to believe that some time this summer we will have a more substantial reopening."