Protection, waning of immunity to COVID-19 after infection, vaccination

Editor's Note

This Israeli study finds that individuals previously infected with COVID-19, regardless of whether they had been vaccinated, had more protection against reinfection than those who were vaccinated (Pfizer-BioNTech vaccine) but previously uninfected.

Among the findings for the number of COVID-19 cases per 100,000 person days since vaccination or previous infection:

• For unvaccinated individuals who had recovered from COVID-19 infection, the rate increased from 10.5 in those who had been infected 4 to less than 6 months previously to 30.2 in those who had been infected 1 year or more previously.
• For individuals who had received a single dose of vaccine after previous COVID-19 infection, the rate increased from 3.7 in those who had been vaccinated less than 2 months previously to 11.6 in those who had been vaccinated at least 6 months previously.
• For previously uninfected individuals who had received two doses of vaccine, the rate increased from 21.1 in those who had been vaccinated less than 2 months previously to 88.9 in those who had been vaccinated at least 6 months previously.

An understanding of the rates of waning immunity after immunity conferring events is important for policy making on the need for and timing of vaccine boosters, the researchers say.