A study examined infections in New York and California last summer and fall and found people who both got vaccinated and survived a bout of COVID-19 had the most protection.

The study examined infections in New York and California last summer and fall and found people who were both vaccinated and had survived a prior bout of COVID-19 had the most protection.

But unvaccinated people with a past infection were a close second.

By fall, when the more contagious delta variant had taken over but boosters weren’t yet widespread, that group had a lower case rate than vaccinated people who had no past infection.

The research does fall in line with a small cluster of studies that found unvaccinated people with a previous infection had lower risks of COVID-19 diagnosis or illness than vaccinated people who were never before infected.

The researchers looked at infections in California and New York, which together account for about 18% of the U.S.

A little under 20% weren’t vaccinated; and roughly 5% were unvaccinated but had a past infection.

— 6-fold lower in California and 4.5-fold lower in New York in those who were vaccinated but not previously infected.

— 29-fold lower in California and 15-fold lower in New York in those who had been infected but never vaccinated.

— 32.5-fold lower in California and 20-fold lower in New York in those who had been infected and vaccinated.