Omicron has spread to California counties according to vaccination rate


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

The increase in cases – which has led to tighter restrictions statewide, event cancellations and the voluntary closure from some bars and restaurants – not surprisingly, given the high transmissibility of the omicron variant and because it infects vaccinated people more easily than previous strains. Moreover, the holiday gatherings were expected to cause a winter push regardless of how the virus developed.

The good news is that COVID-19 vaccines are still holds very well in protection against serious diseases. In San Francisco, where 81% of the population is vaccinated, there is strong evidence of a growing separation between the number of cases and the number of hospitalizations.

During the wave driven by this summer’s Delta Variants, California counties with higher vaccination rates tended to have lower case positivity rates and tests, as shown in the graphs below. While the vaccination rates listed in both tables are up to date, they reflect county-wide vaccination trends that emerged before and during the Delta Surge, as some counties historically had rates higher than that. others. Analysis is limited to counties in California with a population of 100,000 or more, and all figures are from the California Department of Public Health.

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

However, in this current wave of omicron, this clear downtrend line does not exist.

Counties with higher immunization rates still generally have lower hospitalization rates than counties with lower immunization rates, and most experts believe this trend will continue – and may worsen even more – during the winter. While many counties with better immunization coverage now have higher PCR-confirmed case rates than counties with poorer immunization statistics, these numbers likely do not reflect the reality of the situation.

“The most vaccinated counties probably test more, and therefore the lower rates in the less vaccinated counties may be due to failure to detect cases,” wrote UCSF epidemiologist Dr George Rutherford. , in an email.

When using the percentage of positive tests – which at least partly controls the amount of tests performed – there is little association between vaccination rates and transmission levels, indicating that a large number of vaccinated people are infected in the area. But because many of them will have mild or no symptoms, some health experts think officials should use hospitalization figures, not the number of cases, to set public policy.

You can read more about the risk omicron poses to people who have been vaccinated in our article about it.


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