SARS-CoV-2 Reinfection Cases in a Household-Based Prospective Cohort in Rio de Janeiro

Area of Science:

• Infectious Diseases
• Epidemiology
• Vaccinology

Background:

• The emergence of SARS-CoV-2 variants, including Omicron, has raised concerns about vaccine effectiveness against infection and reinfection.
• Understanding the dynamics of COVID-19 reinfection in a vaccinated population is crucial for public health strategies.

Purpose of the Study:

• To investigate the incidence and characteristics of COVID-19 reinfections in a household cohort.
• To evaluate the impact of vaccination status, including booster doses, on the risk of reinfection during different SARS-CoV-2 variant periods.

Main Methods:

• Prospective household cohort study in Rio de Janeiro (April 2020 - June 2022).
• Identification and confirmation of reinfections using laboratory testing and genomic analyses.
• Analysis of vaccination status and its association with reinfection risk across pre-Omicron and Omicron periods.

Main Results:

• Ninety-eight COVID-19 reinfections were identified; 71% confirmed by genomic sequencing.
• Pre-Omicron: One vaccine dose reduced reinfection risk.
• Omicron period: Neither primary vaccination nor booster doses significantly reduced reinfection risk.
• Most reinfections were asymptomatic or milder than primary infections.

Conclusions:

• Vaccination may not fully prevent SARS-CoV-2 infection or reinfection, particularly with newer variants.
• Continuous surveillance of infections in vaccinated individuals is warranted.
• Regular updates to vaccine antigenic targets and booster administration are recommended, similar to influenza vaccination strategies.