ST. LOUIS — On Thursday, the Missouri Department of Health and Senior Services once again reconfigured the state’s COVID-19 data dashboard, adding thousands of previously unreported deaths and infections.

Some date back to the spring of 2020, and many are instances of illness or death now attributed to COVID-19 but that weren’t publicly tallied by the state at the time.

As part of the update, the state also began reporting COVID-19 cases that occurred after vaccination or prior infection. The numbers show that such cases have been remarkably rare, and are most common among those with underlying health conditions.

“This data reaffirms what we have been saying for nearly a year,” new DHSS Director Donald Kauerauf said in a press release Thursday, announcing the update. “COVID vaccines work very well to prevent hospitalizations and death.”

Missouri lags the rest of the U.S. in COVID-19 vaccination rates. Nationwide, 69% of people have received at least one dose of a COVID-19 vaccine, and 59% have been fully vaccinated, according to data from the Centers for Disease Control and Prevention. In Missouri, 57% have received at least one dose and 51% have been fully vaccinated, according to state data.

‘We’ve had to evolve’

On Wednesday, the state reported a total of 12,423 deaths due to COVID-19.

On Thursday, DHSS removed 17 deaths from the total, due to routine data cleaning, spokeswoman Lisa Cox said. But the department also added 2,792 “probable” COVID-19 deaths, boosting the state’s total by 22% to 15,198.

Many of the newly reported virus deaths were identified through antigen tests, commonly called rapid tests, which are less accurate than the slower PCR method. The newly added deaths occurred throughout the course of the pandemic, with the largest numbers in the winter, and during the delta variant-driven wave of infections this spring.

Other state health departments, including the Illinois Department of Public Health — where Kauerauf worked for more than three decades, until last this summer — have long reported probable deaths due to COVID-19.

“We’re learning a lot every day not only about the virus, but about the available testing options and how that plays into these public health definitions for cases and everything,” Cox said. “So as that’s evolved, we’ve had to evolve how we report.”

The department also added two new pages to its COVID-19 dashboard: one reporting cases of reinfection, and another reporting cases after vaccination — a relatively rare phenomenon commonly referred to as “breakthrough” cases.

The data show that 87% of the COVID-19 cases statewide since Jan. 1 have been among people who were not fully vaccinated.

Those who had breakthrough infections were, on average, four years older than the unvaccinated people who caught the virus, the state dashboard says. And a significantly larger portion had underlying conditions that may have weakened their immune response, from chronic kidney disease to diabetes, ischemic heart disease, heart failure and chronic obstructive pulmonary disease.

“This new information is yet another validation that vaccination is essential, and further indicates that continued precautions to avoid infection should be taken,” Missouri Hospital Association President and CEO Jon D. Doolittle said in a press release.

Three-quarters of 1%

In August, unvaccinated people in the U.S. had six times greater risk of testing positive for the virus, and more than 11 times greater risk of dying from it, according to the CDC.

The state on Thursday also began reporting instances of reinfection, another relatively rare circumstance wherein an individual tests positive for the virus, recovers, and then tests positive again after 90 days or more. Until Thursday, the state had been reporting the number of individuals who had tested positive, not the number of cases.

The state dashboard reported 6,581 people caught the virus a second time, or about three-quarters of one percent of all infections. And only 92 people who contracted COVID-19 a second time died.

The breakthrough and reinfection cases are tracked through a collaboration between DHSS and the Missouri Hospital Association. Hospitals share data with the MHA’s Hospital Industry Data Institute, which uses it in aggregate for research and analysis.

Including the new data released Thursday, to date the state of Missouri has logged 888,720 cases of COVID-19 and 15,198 deaths due to the virus.