Neutralizing Antibody-Mediated Protection from Prior Delta Variant Infection Against Omicron BA.5 Sub-Lineage Reinfection One Year Later: A Prospective Cohort Study

Abstract

Background: Previous SARS-CoV-2 infection provides some level of protection against reinfection. However, few studies have evaluated the neutralizing antibody (NAb) response after Delta variant infection and its ability to prevent reinfection with Omicron BA.5 one year later. Methods: This prospective cohort study included 431 patients who recovered from Delta variant infection. We measured their serum NAb titers against both Delta and Omicron BA.5 using microneutralization tests. Results: Over a 17-month follow-up, 17.9% of the participants were reinfected with Omicron BA.5. Younger adults (18–65 years) and individuals who did not receive booster immunization had significantly higher reinfection rates than older adults (>65 years) and those who received boosters (p p > 0.05). Cross-neutralization assays showed a 7.1-fold reduction in NAb efficacy against Omicron BA.5. Conclusions: Delta-variant infection-induced NAbs did not strongly predict protection against Omicron BA.5 reinfection. However, booster immunization effectively reduced the reinfection rate approximately one year after the initial Delta infection.

Keywords

• SARS-CoV-2
• Delta variant
• Omicron BA.5
• reinfection
• neutralizing antibody