Fast Five Quiz: Risk Factors for SARS-CoV-2 Reinfection

Enrico Brunetti, MD


April 14, 2023

The Omicron variant has infected an estimated 3.8 billion people, or 46% of the global population. This is because the Omicron variant has developed numerous mutations that may impair neutralizing antibodies, allowing immune system evasion of the virus and increased rates of reinfection. Compared with the Delta variant, reinfection during the Omicron phase in Italy was 18.1 times higher. In a study assessing protection against symptomatic disease, the effectiveness of pre-Omicron infection against symptomatic BA.4 or BA.5 reinfection was 35.5% whereas the effectiveness of post-Omicron infection against symptomatic BA.4 or BA.5 reinfection was 76.2%. A meta-analysis showed that the rate of reinfection was highest in the Omicron-predominant period (3.31%), followed by the Delta-predominant (1.25%) and Alpha-predominant (0.57%) periods.

Although early reinfection can occur, most cases of SARS-CoV-2 reinfection occur ≥ 90 days after an initial positive test. Protection against reinfection typically is high initially and steadily wanes. A history of COVID-19 has been shown to lower the risk for SARS-CoV-2 reinfection by 84%, particularly in the first 7 months after initial infection.

Learn more about SARS-CoV-2 reinfection.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.