During Sonoma County’s omicron surge, new public health data shows boosters made a real difference

With milder, spring weather approaching and the most recent onslaught of COVID-19 seemingly in full retreat, it’s easy to forget just how pervasive the omicron-fueled winter surge was.

Officially, the omicron surge infected 1 in 13 residents, or 37,341 people, from mid December to mid February. The actual number was likely much larger, as many infections were likely asymptomatic and undetected or detected through rapid testing but never officially registered.

January was a month of rampant viral transmission in Sonoma County, where even those who were fully inoculated became infected at frightening rates. But for most people who received a booster shot, the winter surge was far less worrisome, with much, lower infection, hospitalization and death rates, according to county public health data.

At the peak of the local surge, Jan. 10, unvaccinated residents had a transmission rate of 455.6 new daily cases per 100,000 residents, compared to 127.2 for residents who had either received a booster or were up-to-date in their vaccination status.

Local residents who were fully vaccinated but not yet boosted, even though they were eligible for a third dose, had a transmission rate of 315.7 new daily cases per 100,000 residents.

“We knew that boosters were making a significant difference, particularly with the omicron outbreak,” said Dr. Urmila Shende, the county’s vaccine chief.

Shende she wasn’t surprised to find that boosters had given some local residents a good deal more protection given the scientific data that had been presented on the benefits of boosters.

She said during the winter surge, there was a tendency among some to dismiss COVID-19 vaccines given how many people locally knew others who were becoming infected, even though they’d been fully vaccinated and boosted.

“This anecdotal perspective can make one feel that boosters are not effective,” Shende said in an email. “However, the actual local data available from our recent omicron surge is powerful in demonstrating this protective effect.”

The booster advantage can clearly be seen in county data on COVID-19 transmission over the winter. Beginning in mid-December infections slowly start to climb and begin to spike for both unvaccinated and fully vaccinated residents who, though eligible, had not yet been boosted.

Though infection rates for fully vaccinated, unboosted residents do not reach the levels of unvaccinated residents, they are more than double that of boosted residents. Viewed against the rate of virus spread for unvaccinated residents, the case rate for boosted and up-to-date residents was 28% that of unvaccinated residents. The rate of spread for fully vaccinated residents who were not yet boosted was 69% that of the unvaccinated.

Shende said the recent data is a science-based response to anecdotal stories or perceptions about the ineffectiveness of COVID-19 vaccines. She said she continues to strongly encourage people to get vaccinated and boosted, as COVID-19 will continue to circulate in the local community indefinitely.

“Vaccination and boosters are the best protection we have,” she said.

Residents who are “fully vaccinated and up-to-date” includes those who are still current on their primary vaccination series or have received a booster dose five months after their second dose of a two-shot series (Pfizer or Moderna) or two months after their J & /Janssen inoculation. Those who are “fully vaccinated but not up-to-date” includes those who have been fully vaccinated and are eligible for a booster but have yet not received one.

Kathryn Pack, health program manager for the county’s epidemiology team, said the infection rates for boosted individuals was similar to that of people who were still current on their initial vaccine, with boosted residents having slightly lower case rates, particularly during the omicron surge.

During a COVID-19 briefing this week before the Board of Supervisors, local health officials reported that Sonoma County now has the 10th highest vaccination rate of the state’s 58 counties. Currently, 81% of the county’s residents who are 5 years and older are fully vaccinated; another 7% are partially vaccinated.

Shende told local supervisors that Sonoma County’s current vaccination rate was 10.0% higher than the state’s inoculation rate. Meanwhile, officials said cumulative deaths are roughly 87 per 100,000 residents, a rate that’s 58.2% less than that of the state.

Shende said the success of the local inoculation effort is notable given that the county does run any of its own vaccine clinics, but rather has relied on partnerships with local schools, community-based organizations and large health care providers such as federally-funded heath clinics.

However, county officials acknowledged that more work needs to be done to close the racial and ethnic disparities among those who are currently receiving the booster.

At 48.7%, local Latino residents have the lowest rate of booster inoculations where race or ethnicity is known. In contrast, white residents are 70.7% boosted and Asian have a booster rate of 71%. Black and Native American residents have booster vaccination rates of 59.1% and 59.4%, respectively.

“We know that there is disparity among different ethnic categories and because of that, we are continuing to message through many different means,” Shende said. “A lot of it is through our trusted messengers — community health workers, community based organizations — to help people understand the importance of getting the vaccine.

She said there may be a general perception among some who have been vaccinated that they do not need a booster. She said she hopes the recent data showing the significant advantage of being boosted will encourage more people to get their third dose (or second for those who initially received the J & vaccine).

“I'm hoping that this newer information is going to help people to understand that there's a significant difference in preventing the severe outcomes, specifically of hospitalization and death, particularly for the older age groups,” Shende said.

You can reach Staff Writer Martin Espinoza at 707-521-5213 or martin.espinoza@pressdemocrat.com. On Twitter @pressreno.