How omicron is spreading in California counties with different vaccination rates – SFGate

Many California counties are reporting high COVID-19 cases as the omicron variant spreads across the state.

The case increase which has led to a tightening of restrictions across the state, cancellations of events and the voluntary closure of some bars and restaurants is unsurprising, given the omicron variant's high transmissibility and because it infects vaccinated people more readily than past strains. In addition, holiday gatherings were widely expected to drive a winter surge regardless of the virus' evolution.

The good news is COVID-19 vaccines are still holding up very well in protecting against severe disease. In San Francisco, where 81% of the population is vaccinated, there's strong evidence of a growing separation between case and hospitalization numbers.

During this summer's delta variant-driven wave, California counties with higher vaccination rates tended to have lower case and test positivity rates, as can be seen in the charts below. Though the vaccination rates listed in both charts are current, they reflect countywide trends in vaccination that emerged before and during the delta surge, as some counties have always had higher rates than others. The analysis is limited to California counties with 100,000 or more residents, and all figures come from the California Department of Public Health.

Although the delta variant caused more breakthrough infections than strains that came before, the clear downward trend line on the test positivity graph suggests vaccines offered significant protection against infection and transmission.

However, in this current omicron wave, that clear downward trend line does not exist.

Counties with higher vaccination rates still generally have lower hospitalization rates than counties with lower vaccination rates, and most experts believe that trend will continue and could grow even more pronounced through the winter. While many counties with better vaccine uptake are now posting higher PCR-confirmed case rates than counties with worse vaccination stats, those numbers probably don't reflect the reality of the situation.

"The more vaccinated counties are likely testing more, and so the lower rates in the less vaccinated counties may be a function of failing to detect cases," UCSF epidemiologist Dr. George Rutherford wrote in an email.

When using the percentage of tests coming back positive which at least partly controls for the amount of testing done there's little association between vaccination rates and transmission levels, indicating that large numbers of vaccinated people are getting infected across the region. But because so many of them will have mild, if any, symptoms, some health experts believe officials should be using hospitalization numbers, not case counts, to set public policy.

You can read more about the risk omicron poses to vaccinated individuals in our story on it.

Follow this link:

How omicron is spreading in California counties with different vaccination rates - SFGate