One of the most common reasons Americans cite for not getting vaccinated against COVID-19 is that they're naturally protected by their past infection. When encouraging people who have this belief to get vaccinated, healthcare professionals should explain hybrid immunity and point to studies.
Unvaccinated Americans could benefit from learning that hybrid immunity — natural immunity from an infection combined with the immunity of vaccination — offers stronger protection than a past infection or vaccination alone.
"Against some of the most concerning variants, it's literally 100 times better levels of antibodies after vaccination compared to before for somebody with natural immunity. That's not a small change," Shane Crotty, PhD, a professor at the La Jolla Institute for Immunology in San Diego, told NBC News.
Vaccination reduces the risk of reinfection among people who had a COVID-19 infection by more than twofold, according to a study the CDC released in August.
But relying on previous infection alone as a means of protecting against COVID-19 is especially risky as coronavirus variants continue to emerge, according to Deepta Bhattacharya, PhD, an immunology professor at the Tucson-based University of Arizona.
"Antibody levels are really variable after recovering from infections, and those at the lower end of the spectrum might be more susceptible to reinfections. But after a single vaccine in people who have recovered from COVID-19, antibodies skyrocket up, including those that neutralize variants of concern," he said.
Fikadu Tafesse, PhD, an immunology professor at Oregon Health and Science University in Portland, agreed, pointing to his research that showed that vaccination increased antibody levels against coronavirus variants in people who had been infected with COVID-19.