Breakthrough cases: Here’s how many vaccinated Sacramento County residents got COVID-19
Sacramento County recently began providing data on so-called breakthrough cases of COVID-19 in fully vaccinated residents, and the early numbers appear to affirm the high efficacy of the jabs.
County health officials in an update to their coronavirus data dashboard this week said 152 patients have tested positive this year, out of more than 433,000 considered fully vaccinated through last Friday. That’s about 0.035%, or one in about every 2,850 residents who have received two doses of Pfizer or Moderna, or one dose of Johnson & Johnson.
Of those 152, only 29 of the cases were symptomatic. That means there has been about one symptomatic case reported for every 15,000 fully vaccinated recipients, or 0.007%.
“It’s a very, very small percentage of people who are getting vaccines who are getting infected with COVID,” Jamie White, the county’s epidemiology program manager, said during a Thursday teleconference with local reporters. “I’d like to say that’s about, or even less than, what we would expect.”
White said the national Council of State and Territorial Epidemiologists’ definition of a “breakthrough case” requires it be a symptomatic case but that the county dashboard will continue track both totals for transparency.
By contrast, there have been more than 100,000 cases in Sacramento County residents who were not fully vaccinated, including about 34,000 since Jan. 1. The 2021 total ranges somewhere between 2% and 3% of that group depending on the precise timing of those positive cases in relation to Sacramento’s vaccine progress, or one case for every 33 to 50 residents.
At a glance, this appears to show that unvaccinated or partially vaccinated residents have tested positive for COVID-19 at a rate roughly 60 to 85 times higher than those who’ve been fully vaccinated since the start of 2021.
Comparisons of the rates are rough, though, because community transmission rates are much lower now than they were in the earliest weeks of the vaccine campaign, and they started declining even before a significant percentage of residents were fully vaccinated.
For instance, by the end of January — a month in which the infection rate was still very high amid the winter surge — only about 23,000 Sacramento County residents were fully vaccinated, state health data show. By the end of February, the county’s daily case rate was less than half as high as late January, even as less than 7% of its population was fully vaccinated, state and local health data show.
White said she did not immediately know whether any of the 29 symptomatic breakthrough cases had been hospitalized for COVID-19 or died, but said she would provide that information soon.
The county also notes on its data dashboard that the numbers are subject to change, with the 152 breakthrough cases a preliminary number.
State health officials recently reported that, between Jan. 1 and April 28, there were 3,084 breakthrough cases out of 12.9 million fully vaccinated Californians. That’s about 0.024%, relatively close to Sacramento’s local total.
