Risk of BA.5 Infection among Persons Exposed to Previous SARS-CoV-2 Variants

Evolution of antibody immunity following Omicron BA.1 breakthrough infection

“…Thus, convergent D614G/BA.1 cross-neutralizing antibodies recognize epitopes commonly mutated in recently emerging Omicron sub-variants, providing a molecular explanation for the high degree of antigenic convergence observed in recent Omicron sub-variant evolution and their increased level of immune evasion relative to BA.1. In summary, BA.1 breakthrough infection in mRNA-vaccinated individuals induces broadly neutralizing serological and MBC responses that persist for at least six months after infection, supporting real-world studies showing that BA.1 breakthrough infection provides protection against symptomatic BA.1, BA.2, and BA.5 infection for at least 5-6 months (14)(15)(16). Furthermore, although the acute B cell response following breakthrough infection is primarily mediated by recall of cross-reactive vaccine-induced MBCs, these MBC clones accumulate somatic mutations and evolve increased breadth and potency for at least 6 months following infection.…”

Higher risk of SARS-CoV-2 Omicron BA.4/5 infection than of BA.2 infection after previous BA.1 infection, the Netherlands, 2 May to 24 July 2022

“…The reduction in protection from previous infection seems mainly driven by escape from BA.1-induced protection. Others argued that the large number of reinfections with BA.5 is caused by the large pool of BA.1 infections [16]. However, we show that also immune escape plays a role in the large number of reinfections with BA.5.…”

Hybrid immunity and strategies for COVID-19 vaccination

“…2,4 Overall, the data suggested that breakthrough infections with the BA.5 subvariant were less likely to occur among people with a previous SARS-CoV-2 infection history in a highly vaccinated population, especially for previous BA.1 or www.thelancet.com/infection Published online September 21, 2022 https://doi.org/10.1016/S1473-3099(22)00640-5 BA.2 infection, than among people with no previous primary infection. 6 These data provide immunological context for the importance of hybrid immunity in managing the current surges caused by the BA.2.12.1, BA.4, and BA.5 subvariants in populations with high frequencies of vaccination and BA.1 or BA.2 infection. [2][3][4][5][6] Another important factor in reducing infection risk is heterologous booster vaccination with different platforms to maximise the breadth of vaccine-induced immunity, especially in countries primarily using inactivated vaccine; T-cell immunity is not affected by changes in spike protein and remains effective in preventing severe disease, hospitalisation, and death.…”