Neutralizing Antibody Responses After SARS-CoV-2 BA.2 and BA.2.12.1 Infection Do Not Neutralize BA.4 and BA.5 and Can Be Blunted By Nirmatrelvir/Ritonavir (NM/r) Treatment

Abstract The factors contributing to the rapid emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) BA.4 and BA.5 subvariants in populations that experienced recent surges of BA.2 and BA.2.12.1 infections are not understood. Neutralizing antibodies (NAbs) are likely to protect against severe disease if present in sufficient quantity. We found that after BA.2 or BA.2.12.1 infection, NAb responses were largely cross-neutralizing but were much less effective against BA.5. Additionally, infected individuals who were treated early with nirmatrelvir/ritonavir (NM/r) (Paxlovid™) had lower NAb levels than untreated individuals.