Prior COVID-19 infection protects against reinfection with Delta and Omicron variants

A recently published study in the journal, Annals of Internal Medicine, reported robust antibody response and sustained protection against reinfection with Delta and Omicron variants after prior infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This study addressed the evidence gaps in previous reports regarding the duration and durability of antibody response after prior infection with the wild-type strain or the Alpha variant of SARS-CoV-2 and reinfection risk.?

A review of 29 observational studies was carried out. The included studies evaluated immunoglobulin G (IgG) antibody duration at least 12 months after SARS-CoV-2 infection, antibody response among immunocompromised adults, predictors of nonseroconversion, and reinfection risk. Key findings are highlighted in the graphic below –

Clinical implication: Sustained antibody response is observed against the Delta and Omicron variants after previous infection with the older variants. However, protection against reinfection with the Omicron BA.1 or BA.2 variant was lower and waned rapidly over time after previous infection with the Delta variant or the older variants. In addition, protection against Omicron BA.4 or BA.5 was observed for up to 4 months after Omicron BA.1 or BA.2 infection. This data suggests the ability of the variants to evade the immune system despite considerable antibody response. One important observation is that although seroconversion is associated with protection against reinfection, antibody levels are inadequate in assessing the degree of protection from reinfection. Besides, the role of antibody testing to predict the risk of reinfection is uncertain.

(Reference: Holmer HK, Mackey K, Fiordalisi CV, Helfand M. Major update 2: Antibody response and risk for reinfection after SARS-CoV-2 infection-Final update of a living, rapid review. Ann Intern Med. 2022:M22-1745. Doi: 10.7326/M22-1745)