The number of vaccinated Clark County residents who have tested positive for COVID-19 surged by 74 percent in two weeks, according to the latest data from Clark County Public Health.
The new data also shows lower levels of serious illness or death among the so-called breakthrough cases compared with those not fully vaccinated, with no new deaths from breakthrough cases in the past two weeks and only five since vaccines first became available in February.
On Thursday, Public Health reported 1,022 breakthrough cases since February, up 435 cases from the 587 cases reported on Aug. 5. The breakthrough cases accounted for 16.8 percent of the 2,585 new COVID-19 cases reported between Aug. 5 and Thursday, according to Public Health data.
The increase in breakthrough cases comes as the highly contagious delta variant becomes the dominant version of the SARS-CoV-2 virus in Washington. Data isn’t available at the county level, but state health officials reported this week that genetic sampling shows that 95 percent of all new COVID-19 cases statewide are caused by the delta variant.
Citing the rapid increase in caseloads and hospitalizations around the state, Gov. Jay Inslee this week imposed new mandates requiring all public, charter and private school teachers and staff — as well as those working at state colleges and universities — to be fully vaccinated by Oct. 18 or risk losing their jobs.
Inslee also expanded the state’s mask mandate, effective Monday, to require all persons to wear masks in nearly all indoor settings regardless of their vaccination status. He also strongly recommend masks for crowded outdoor settings such as outdoor concerts, fairs and farmers markets.
Data on breakthrough cases is underscoring arguments made by public health officials that, even with the delta variant, COVID-19 vaccines continue to be highly effective at preventing severe illness that can lead to hospitalization and death.
In its latest data as of Thursday, Public Health said the number of breakthrough cases experiencing symptoms rose 113 percent over two weeks, from 359 to 765 cases since February.
The number of breakthrough cases requiring hospitalization, however, rose by only 20.5 percent over two weeks — from 39 to 47 cases — and the number of deaths over two weeks from breakthrough cases was unchanged at five.
Since February, the county has added 12,514 new COVID-19 cases, according to Public Health data. The data shows that 91.8 percent of those cases and 95.7 percent of deaths from COVID-19 in that period occurred in people who had not been fully vaccinated.
All told, of the 242,897 people in Clark County vaccinated as of Monday, only 0.4 percent has tested positive for COVID-19, according to Public Health data.
As of Monday, 63.5 percent of Clark County residents age 12 and older had at least one dose, and 57.2 percent were fully vaccinated, according to Public Health data.
COVID-19 vaccine is available at no charge at many local pharmacies and medical providers.
Note: An earlier version of this story contained an error that has since been corrected.