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Today, we will start reporting the state’s 14-day case rate for Pierce County

The state currently uses a 14-day COVID-19 case rate as one of two factors to determine if a county is in Phase 1, 2, or 3 of the Roadmap to Recovery plan.

As Pierce County case rates began rising in March, the threat of being moved from Phase 3 to Phase 2 increased. Many of you noticed differences between the state’s reported case rate and our own reporting.

In the past, those differences were relatively small. But for several reasons, those differences have increased. The state rate is now 25% higher than what our local data shows.

We’ve always been open about why those differences exist. We’ve answered questions when asked and responded on social media. We want to provide more clarity on Roadmap to Recovery metrics on which our phase movement depends. Today, we will discontinue our COVID-19 case rate reporting method and instead post and track the state’s case rate metric for Pierce County.

Probable cases

The 14-day COVID-19 case rate is the number of cases per 100,000 people in the population over a 14-day period. To get our number, we add the number of confirmed cases over a 14-day period, divide them by the latest Pierce County population figure, a little over 900,000, and multiply by 100,000.

We and the state use the same formula for that equation. The difference comes in how we count the number of cases, who we count, and when we count them.

At the beginning, we and the state only counted positive confirmed cases. Over time antigen tests became available. People could access these tests easily and get results in 15 minutes. But the CDC recommended, because of reduced accuracy of antigen tests, a follow up PCR test as an extra step of the antigen test for some people. Public health labeled positive antigen tests as “probable” positive cases.

In December 2020, the state began including these probable cases in its case rate. While we reported the number of these antigen positives, we kept them separate from our confirmed PCR cases and did not include them in our case rate calculations.

Over time, antigen tests have become more popular, and not all people who test positive follow up with PCR tests to confirm those results. In February, the difference between our reported case rate and the state’s was 10%. That has since grown to 25%.

While other definitions of probable cases exist, these positive antigen tests are the only probable cases the state reports.

JBLM cases

In March 2020, the Department of Defense (DOD) requested we not include cases on JBLM in our regional case counts because of security concerns. While we continued to receive data on these cases, we have always honored the request and not reported cases living on the base. We include any positive case affiliated with the base that does not live on base in our Pierce County regional breakdowns.

Because the state includes the JBLM cases with all other state data with no regional breakdown, the same DOD security concerns do not apply. The state includes those cases in its case rate.

Differences in timing

We include a 6-day data lag and the state currently includes an 8 to 10-day data lag. The lags allows time to remove any case duplicates or remove cases mistakenly reported as Pierce County, or in the state’s case, out of state residents. 

The state also uses lab specimen collection date as the case date. We use the date we received the cases at the Health Department.

The trend is the same

Regardless of which dashboard you’ve followed, the clear pattern is Pierce County cases continue to rise and so does our case rate. Now that everyone 16 and older are eligible for the COVID-19 vaccine, our best strategy to overcome COVID-19 is for people to get vaccinated.

We need about 75% of our population to get vaccinated to achieve community immunity. Those 15 and under are not yet eligible. But everyone 16 and up is. Do your part to protect yourself, your family and your community—and help us all make faster progress to more mask-free living.

Appointments are easy to find. Vaccine is always free. You don’t need insurance, ID or a primary care physician. Walk in opportunities are also available. And if you can’t leave home, we’ll bring vaccine to you. Learn more at  tpchd.org/vaxtothefuture.

Keep doing the things that keep you, your family, and your community safe: