Is the winter COVID-19 surge sputtering, and are we reaching herd immunity?

It’s early yet, but there are signs the dreaded holiday surge in COVID-19 cases may be losing steam, with cases and deaths at a fraction of the levels seen around the same time in 2020 and 2021.

And that’s with nearly all pandemic restrictions lifted and far fewer people heeding pleas from health officials to wear masks and stay “up to date” on the latest COVID vaccine booster.

“I think we can say compared to the last two years at this time of the year, COVID is not nearly the same stress on the health care system and morbidity and mortality on the population,” said Dr. John Swartzberg, clinical professor emeritus of infectious diseases and vaccinology at UC-Berkeley’s School of Public Health.

The CDC reported 487,000 weekly cases across the U.S. as of Dec. 14. There were more than twice as many reported a year ago and three times as many — 1.5 million — reported Dec. 23, 2020.

The trend is similar in this year’s reports on COVID hospitalizations and deaths in California and across the country.

For example, the number of weekly deaths reported by the CDC as of Dec. 20 — 2,952 — was about one-sixth the number in 2020. California’s seven-day average death rate per 100,000 residents was only 0.01 as of Dec. 18 — that’s well below the 0.2 rate last year and the 0.9 rate in 2020.

“As of now there does seem to be a smaller wave this winter compared with the prior two winters,” the California Department of Public Health said Thursday.

What’s going on? Have we finally reached the elusive “herd immunity” we’d once hoped for with this virus? Alas, it’s not that simple.

Scott Pauley, a spokesman for the Centers for Disease Control and Prevention, said the nature of the fast-mutating virus and our bodies’ response to it makes it impossible to reach a level of immunity throughout communities that would block its transmission.

“Both infection-induced and vaccination-induced protection against infection are not 100% effective at reducing transmission, and those protections wane over time,” he said.

That doesn’t mean that immunity from prior infection and vaccination isn’t playing a role in reducing the virus’ impact this winter, said Dr. Peter Chin-Hong, an infectious disease specialist at UC-San Francisco.

What drove last winter’s massive surge in cases was a new, fast-spreading virus variant, dubbed omicron, that arrived just before the holidays. The COVID viruses circulating today aren’t quite the same but still are in the omicron family. With so many people having already been infected with omicron over the past year, they retain a measure of protection even though it fades with time.

“I think we’re still relatively protected as a community from all these waves of infection,” Chin-Hong said.

Pauley added that while the omicron virus variant spreads more easily than earlier variants, it generally causes less severe illness and death. And Chin-Hong noted that widely available therapeutics such as Paxlovid have been shown to reduce the severity of symptoms, tamping down hospitalizations and deaths.

The new COVID-19 vaccine booster released in the fall, which just 14% of the U.S. population and 17% in California have received, is tailored to provide added protection against omicron variants. Pauley said early data has shown that the updated COVID-19 vaccine may reduce risk of severe COVID-19 cases that could lead to hospitalizations or death by 50% or more.

Today’s reported number of cases is presumed to be an undercount, as most people are using rapid at-home antigen tests to confirm COVID-19 infections these days and not reporting the results. Fewer than 2.5 million weekly molecular COVID tests were done as of Dec. 14, compared with more than 11 million weekly tests the same time last year.

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