Mayo Doctor says too soon to tell if U.S. is approaching endemic stage of COVID-19

Cases of COVID-19 are dropping across the country, but it’s too soon to know whether the pandemic is transitioning into an endemic stage.

"An endemic refers to a disease that's present at a certain level in a population, either at certain times of the year or year round," said Dr. Jack O’Horo, an infectious disease specialist at Mayo Clinic in Rochester.

O’Horo explained that one of the best examples of an endemic virus is the seasonal flu. With the flu, he says there is an expected level of increased infections every winter that public health leaders accept as a normal variation. In all likelihood, he believes that we are heading toward such an endemic.

"Determining where we cross into that threshold is a question that epidemiologists and others will have to answer in coming weeks, because determining what that background level is will require some real research and looking at these numbers," said O’Horo.

Cases across the country and even in Minnesota are falling fast after the omicron variant caused a rapidly fast third wave of infection after the holiday season. Data shows the seven-day average of new cases in Minnesota spiked during the last week of January. 

Likewise, the testing of wastewater in the Twin Cities by the Metropolitan Council shows the viral load in sewage started dropping well before positive test results spiked. 

When the virus eventually reaches the endemic phase, Dr. O’Horo believes people will still need to get vaccinated.

"There is going to be a need for some sort of periodic vaccination," said O’Horo. "It's something where we're likely to see new variants like we've seen all along and likely to need new vaccines for those variants. And I wouldn't be surprised to see something very similar to what we see with needing a seasonal shot the way we do for the flu."

Dr. O’Horo expects the immunity from both vaccines and the recent infections from omicron will contribute to a continuing drop in infections through the spring and into the summer. But among the unvaccinated who were infected with omicron, it’s unclear how long that natural immunity will last.

"This is why I keep coming back to saying that as we look to the fall, it will be very important to look towards what kind of vaccine options are available to boost individuals and prevent another wave from coming back," said O’Horo.