Back in the early days of sourdough starters and masked neighborhood strolls, we suspected Covid could only be contracted once. As the pandemic progressed, experts estimated natural immunity would last six months. Then 90 days. Now it’s all a guessing game with the emergence of new variants like BA.5.

John Bowen, a biochemist at UW Medicine, has been searching for elusive answers about Covid reinfections and immunity as the ever-changing pandemic unfolds—especially as research shows that a person's risk for complications like stroke, heart attack, diabetes, long-term cognitive impairment, and long Covid increase with each Covid infection, even asymptomatic cases.

According to Bowen and his team, it’s clear that contracting Covid does provide a “solid period” of natural immunity, but the exact length of time depends on the health, biology, and vaccination status of the person infected, as well as which variant was contracted.

There is some evidence that suggests a prior infection could confer different—perhaps more—immunity than vaccines alone, as cells in the nose and mouth retain memory of the virus and act as a first line of defense. But outcome data from Public Health—Seattle and King County shows those who are vaccinated and boosted are better protected from hospitalization and death.

Either way, reported reinfections have been slowly trending upward since spring. Bowen attributes this growth to three factors: the emergence of new variants that are more vaccine evasive than the original coronavirus strain, waning immunity in folks who haven’t gotten vaccinated or boosted recently, and societal factors like less masking and fewer restrictions.

As Bowen and other researchers continue searching for answers, we can keep tabs on reported reinfections in the state from the Department of Health's Covid data dashboard.