'Herd immunity' may be more complex than reaching high vaccine rate
By April Ehrlich
The COVID-19 booster is now available to all adults in Oregon.
The Oregon Health Authority made the announcement on Nov. 20, a day after the Centers for Disease Control and Prevention announced similar federal guidelines.
The news comes after a weeks-long decline in COVID cases across the state. Case numbers are about half what they were at the peak of the Delta surge in September; COVID-related hospitalizations are down to about 400 patients. By contrast, there were 1,178 COVID patients in Oregon on Sept. 1.
Nonetheless, state health officials say there's still a long road ahead.
"While we can feel really good about the numbers having come down, they're not where any of us would like to be in terms of the level of severe disease and even the level of folks who are getting sick," Dr. Dean Sidelinger, Oregon's state health officer and epidemiologist, said.
Projections show a continued slow decline in hospitalizations through winter, Sidelinger added, but "what we don't know is what kind of little surges we're going to have on top of that."
Those surges could result from people getting together for the holidays and they could be surges from both COVID and influenza. Flu-related hospitalizations in the United States last year were lower than they'd been since data collection started in 2005.
That trend is likely to change this year, Sidelinger said, because more people are mingling than they were last year when coronavirus vaccines weren't yet available.
"So, how COVID behaves, how influenza behaves — as the weather's colder and people are spending more time inside — will all have an impact on hospital capacity," Sidelinger said. "Likely, some level of wearing masks will be with us at least into the beginning of the year, if not longer."
As of Nov. 20, more than 73% of eligible Oregonians had received a full dose of the coronavirus vaccine. Since the start of the pandemic, health experts have said "herd immunity" — when most of the population is resistant to a disease — could be reached when 60% to 70% of the population is resistant to the coronavirus.
Still, Sidelinger said the idea of herd immunity is more complicated than that, especially considering the highly transmissible Delta variant.
"It's hard to give a specific number on, 'If we reach x percentage, we're at herd immunity," he said.
Booster doses will also eventually factor into the equation. Sidelinger said national health data show that the initial vaccines are still effective and most people who aren't at a high risk of contracting COVID don't have to worry about waning efficacy. Eventually, though, health experts will transition into gauging a population's overall immunity by the number of people who've received a booster dose.
As for getting together with loved ones over the holidays, Sidelinger said vaccines will provide essential protection to people visiting family and friends. He still recommends that vaccinated people take extra precautions, like wearing masks and keeping groups small, mostly to protect people who are at a high risk of contracting COVID.
He also said people shouldn't shy away from asking their guests if they are vaccinated. If you're nervous about asking relatives about their vaccination status, Sidelinger suggests framing the question around protecting everyone at your gathering, including people who are over the age of 65 or immunocompromised.
"If you have someone in the group who's immunocompromised, or who is at a high risk for COVID, think about the plans that you're making," he said. "Can you reduce that risk? Can you postpone that get together with the folks who are not vaccinated? Can you move things outside?"
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