Immune response to SARS-CoV-2 variants of concern in vaccinated individuals

TLDR

SARS‑CoV‑2 is rapidly mutating, especially in the receptor‑binding domain, raising concerns about cross‑protection between strains after vaccination or infection. The study collected serum and saliva from vaccinated (Pfizer BNT‑162b2), infected, and uninfected participants and measured antibody binding to RBD mutants of emerging variants. Vaccinated individuals displayed strong humoral and salivary IgG responses after the second dose, yet neutralization and binding to RBD mutants, particularly the South African variant, were markedly reduced, underscoring the need for continued surveillance and vaccine updates.

Abstract

SARS-CoV-2 is evolving with mutations in the receptor binding domain (RBD) being of particular concern. It is important to know how much cross-protection is offered between strains following vaccination or infection. Here, we obtain serum and saliva samples from groups of vaccinated (Pfizer BNT-162b2), infected and uninfected individuals and characterize the antibody response to RBD mutant strains. Vaccinated individuals have a robust humoral response after the second dose and have high IgG antibody titers in the saliva. Antibody responses however show considerable differences in binding to RBD mutants of emerging variants of concern and substantial reduction in RBD binding and neutralization is observed against a patient-isolated South African variant. Taken together our data reinforce the importance of the second dose of Pfizer BNT-162b2 to acquire high levels of neutralizing antibodies and high antibody titers in saliva suggest that vaccinated individuals may have reduced transmission potential. Substantially reduced neutralization for the South African variant further highlights the importance of surveillance strategies to detect new variants and targeting these in future vaccines.