Hybrid Immunity Provides Protective Advantage Over Vaccination or Prior Remote Coronavirus Disease 2019 Alone

Area of Science:

• Immunology
• Epidemiology
• Public Health

Background:

• The protective effects of prior COVID-19 infection combined with vaccination are not well understood.
• Prior infection alone may offer some protection, but its extent relative to vaccination is unclear.

Purpose of the Study:

• To determine if messenger RNA (mRNA) vaccine doses provide additional protection in patients with prior COVID-19 infection.
• To compare the protective efficacy of infection alone versus infection plus vaccination.

Main Methods:

• A retrospective cohort study analyzed COVID-19 risk from December 2020 to March 2022.
• Included vaccinated and unvaccinated individuals of all ages, with and without prior infection.
• Used hazard plots and multivariable Cox regression to assess infection risk.

Main Results:

• Individuals previously infected and vaccinated had the lowest cumulative incidence of COVID-19.
• Vaccination reduced reinfection risk by 26%-36% in previously infected individuals compared to unvaccinated, infected individuals.
• Higher incidence of COVID-19 was observed in uninfected and unvaccinated individuals.

Conclusions:

• Vaccination is associated with a reduced risk of COVID-19, even in individuals with a history of infection.
• Encouraging vaccination for all, including those with prior infection, is recommended.
• Vaccination is crucial given emerging variants and the availability of variant-specific boosters.