High Post-Infection Protection after COVID-19 among Healthcare Workers: A Population-Level Observational Study

Area of Science:

• Infectious Diseases
• Epidemiology
• Immunology

Background:

• Limited understanding of post-COVID-19 immunity and reinfection rates persists.
• Healthcare workers (HCWs) are at high risk for SARS-CoV-2 exposure.
• Evaluating COVID-19 features and protection in HCWs is crucial.

Purpose of the Study:

• To assess post-infection immunity and COVID-19 characteristics in HCWs.
• To determine the rates of SARS-CoV-2 reinfection, reactivation, re-positivity, and severity.
• To evaluate protection against repeat infections following initial COVID-19 illness.

Main Methods:

• Cross-sectional, population-level observational study of HCWs in Fars Province, Iran (April 2020 - February 2021).
• Utilized polymerase chain reaction (PCR) testing to determine infection rates.
• Re-infection evaluated after a 90-day interval.

Main Results:

• Over 30,000 PCR tests were conducted, with a 61.94% infection rate among HCWs.
• Reinfection occurred in 1.81% of total HCWs, with 97 cases identified after 90 days.
• Estimated protection against reinfection was 94.8%; no significant difference in symptoms or ICU admission was observed between first and subsequent infections.

Conclusions:

• SARS-CoV-2 re-positivity, relapse, and reinfection are infrequent in HCWs.
• A single COVID-19 infection confers substantial immunity, estimated at 94.8% protection against recurrence.
• Findings highlight the protective effect of prior infection in HCW populations.