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DENVER (KDVR) — Have you had COVID-19? What about the vaccine? Maybe you’re one of the people who have both types of immunity. But as it turns out, even souped-up immunity from several sources wears off eventually.

U.S. health officials recommend COVID booster shots for Americans eight months after their second dose of the Pfizer or Moderna shot. Available evidence suggests that’s about the amount of time it takes for both vaccine immunity and prior exposure immunity to wear off.

This means even Coloradans with two levels of immunity will, at some point, need a booster.

Data and studies are scarce, but the available evidence suggests that those who have both been previously infected with COVID and vaccinated have heightened immunity.

Neither the U.S. Centers for Disease Control and Prevention nor the Colorado Department of Public Health and Environment tracks the exact number of people who have been both infected and vaccinated.

The best estimate available is simply an assumption. In Colorado, there have been 593,562 cases to date along with 3.25 million fully vaccinated people. Some will be both vaccinated and previously infected.

Two studies together suggest that vaccinated persons who were previously infected have extra immunity.

A recent CDC study shows that vaccinated people who had been previously infected were 2.34 times less likely to become infected again compared to unvaccinated people who had been previously infected.

The study’s authors acknowledge some gaps in what their findings can tell us.

This was a limited case study from Kentucky, with small numbers of people and timeframe. Furthermore, the data comes from May-June, which is before the delta variant became the nation’s dominant strain.

The second study, from international medical journal The Lancet, was larger in scope and narrower in focus. Taken from patients all over the British Isles, it only looked at the reinfection rate for those who previously had COVID.

The study found that individuals who had gotten COVID before had an 84% lower risk of reinfection, which lasted about seven months.

Together, these studies suggest that people who have been sick and been stuck will have heightened immunity, but also that it will wear off in the space of a year.