Oregon public health officials say the delta variant of COVID-19 poses an urgent threat to more than 1.5 million Oregonians who aren’t yet vaccinated.
“My message today is to people who have not yet been vaccinated: You are in harm’s way,” state epidemiologist Dr. Dean Sidelinger said at a Thursday press conference.
Statewide, case rates, test positivity rates and hospitalizations due to COVID-19 are all rising; a reversal that comes just months after the state beat back a wave of infections due to the alpha or UK variant, and weeks after Oregon fully reopened its economy.
Between June 1 and July 1, the daily average number of cases more than doubled, from 181 per day to 378 per day, Sidelinger said. Hospitalizations and test positivity rates have also risen.
While sounding the alarm, OHA Director Pat Allen also suggested that his agency will play less of a front and center role, at least publicly, in the pandemic response and ongoing public vaccination campaign.
He noted that infection rates are highest in counties with lower vaccination rates, and at one point described the situation as “not a statewide challenge.” Vaccination rates in Oregon range from a low of 37% in Lake County to a high of 75% in Washington County.
“A localized pandemic demands effective localized public health interventions, not a statewide response,” he said. “OHA stands ready to help local leaders and local public health officials in places where COVID-19 is running rampant due to low vaccination rates.”
Republicans dominate the politics of many rural Oregon counties that have lower vaccination rates, and some GOP leaders have frequently spared with Democratic Gov. Kate Brown over COVID-19 restrictions — and more recently, a state law that empowers teens to be vaccinated without needing parental consent.
Allen acknowledged that the politicization of the virus and virus response has made it harder for OHA to influence vaccination rates in some parts of the state.
Allen said OHA will provide counties that need more support with vaccine does, testing, and other aid. But he urged county leaders to engage more with the public.
A spike as schools start?
Three of Oregon’s top scientists studying COVID-19 say the delta variant is poised to cause a new, sustained wave of infections in the state — just as schools are set to open to full-time, in-person instruction this fall.
“Public health and educational authorities have been planning based on the idea that COVID is going away, and it’s not. It’s coming back in a more infectious form,” said Brett Tyler, director of the Center for Quantitative Life Sciences at Oregon State University.
Tyler co-leads the TRACE project, a COVID-19 surveillance program that tests community wastewater and conducts door to door sampling surveys to better track the pandemic in Oregon.
In data his project collected in the last week of June, they detected the delta variant in 60% of samples.
“It’s basically in all parts of the state we’re monitoring,” he said — including communities in Northeast Oregon, the Willamette Valley and Southern Oregon.”
The delta variant first emerged in India in December 2020, spreading quickly among the unvaccinated population there. It was detected in the U.S. in March and is now responsible for the overwhelming majority of new cases.
Genomic sequencing of clinical samples collected from people getting tested or treated for COVID-19 in Oregon showed that in the first week of June, the delta variant accounted for about 5% of cases here. By the first week of July, its share had climbed to about half of all cases in the state.
“This is the most contagious form of COVID-19 that we’ve identified to date,” said Dr. Brian O’Roak, who co-leads the Oregon SARS-CoV-2 genome sequencing center at OHSU.
“It’s able to spread much more quickly — especially in the unvaccinated parts of the state and communities it could spread like wildfire.”
The two-dose mRNA vaccines approved for use in the U.S. appear to be highly effective at protecting people exposed to the delta variant from symptomatic infection, hospitalization and death. However, new research suggests the one dose J&J vaccine may be less effective protection against it.
Scientists say by getting vaccinated, Oregonians have already blunted the impact of the coming surge — and anyone on the fence should consider getting vaccinated as quickly as possible.
“We’ve protected a large fraction of the state from severe illness and death, and that’s something that should be applauded and has made a major difference,” O’Roak said.
But the arrival of the variant has effectively moved the goalposts of Oregon’s vaccination campaign.
Peter Graven, director of advanced analytics at OHSU, leads the university’s COVID-19 modeling effort.
He estimates that about 66% of Oregon’s population has gained immunity to COVID-19, through vaccination or past exposure to the virus.
If we were still dealing with the original virus, that 66% is close to herd immunity — enough protected people to starve the virus of opportunities to transmit itself and keep case counts low, even as masks came off and life started to return to normal.
With its higher degree of transmissibility, the delta variant changes the calculation of how many people need to be vaccinated to block transmission of the virus to the unvaccinated and those with weak immune responses to vaccines.
“When we talk about it spreading faster, it also raises the level of immunity needed to stop it growing. If you only have a few people around you who are not immune, it’s going to find them,” Graven said.
Graven says the reproductive rate of the delta variant appears to be around 7, compared to 2-3 for the original virus and around 4 for the alpha or UK variant.
That means that without interventions like mask-wearing, a person infected with the original virus would have spread it to three other people, on average. With the delta variant, each person spreads the virus to seven others.
With that rate of reproduction, he estimates the virus will continue to spread until about 85% of Oregonians have immunity through vaccination or infection.
Scientists are particularly worried about two groups as the wave of infections breaks across Oregon: People in communities with low vaccination rates, and children under 12, who can’t get vaccinated yet.
“My greatest concern is school-aged children,” Tyler said. “Elementary school children are little infection machines in the best times, and then you add the delta variant into that, and none of them being vaccinated — I’m very very concerned about this fall.”
To date, most children with COVID-19 have only mild symptoms if any; the disease poses far greater risks to older adults.
However, Tyler notes that the delta variant is still relatively new and scientists have had little time to understand how it may differ from the original virus.
One new study has elevated his concern: research showing the amount of virus in the respiratory tracts of people with the delta variant is 1,000 times higher than it was for people infected with the original version.
Tyler said without more data, it’s unclear whether the delta variant could be more easily transmitted by children than the original variant, or whether it might make some of them sicker.
“What we know about children may not be that accurate any more,” he said.
He expects more data on the delta variant in children to be shared by researchers in the United Kingdom and Israel in the next month or two.