Yolo County has seen a steady decline in daily new COVID-19 cases over the last 10 days and now finds itself on the verge of yellow. The county could enter the least-restrictive yellow tier of the state’s color-coded blueprint next week, provided case numbers and test positivity rates remain low. Moving to yellow will allow for greater indoor capacity at many businesses, including gyms and fitness centers, movie theaters and museums. However, the county’s stay in yellow would likely be short-lived — the state is poised to ditch the tier-based system altogether just three weeks later, lifting all restrictions on businesses and activities on June 15. Nevertheless, moving to yellow marks a step forward for Yolo County, which has been reporting stubbornly high case rates for a couple of weeks, something officials had blamed in part on the UK variant circulating locally. But in the battle of vaccines versus variants — which is playing out across the globe — vaccines seem to be getting the upper hand in Yolo County, where 52 percent of all residents have now received at least one dose of a COVID-19 vaccine and cases are now declining. The county’s adjusted daily new case rate this week was 1.8 per 100,000 residents, down from 3.3 the week before. The countywide test positivity rate also declined from 0.7 percent to 0.4 percent, and the health equity quartile metric, which measures test positivity in the county’s most disadvantaged areas, declined from 1.9 percent last week to 1.6 percent this week. All three metrics now meet the requirements of the yellow tier. The county continues to benefit from the enormous amount of testing done by Healthy Davis Together and on the UC Davis campus. The state gives a bonus to counties that test more than the state average, a bonus that drives Yolo County’s actual case rate — which at 3.5 currently meets the orange tier metric — down to an adjusted case rate that meets the yellow tier metric of below 2 per 100,000 residents. Absent that bonus, the county would not be on the verge of yellow but would remain in orange like a couple neighboring counties that have actual case rates the same or lower than Yolo. Napa County, for example, also has an actual case rate of 3.5, but because that county administers significantly fewer tests than Yolo — 487.8 per 100,000 residents versus Yolo’s 1,187.3 tests per 100,000 residents — Napa’s adjusted case rate of 2.6 keeps the county in orange. Colusa County has an actual case rate below Yolo’s — 2.5 per 100,000 residents — but tests far less than Yolo (212.5 per 100,000 residents) keeping its adjusted case rate at 2.5. The statewide actual daily new case rate is 3.2, below Yolo’s 3.5.