Omicron extensively but incompletely escapes Pfizer BNT162b2 neutralization

TLDR

The emergence of the SARS‑CoV‑2 Omicron variant may compromise vaccine effectiveness and lead to re‑infections. The study examined whether Omicron evades neutralization by antibodies from South African individuals vaccinated with Pfizer BNT162b2. Blood samples collected shortly after vaccination from both previously infected and infection‑naïve individuals were used to assess neutralization. Live Omicron was isolated and shown to use ACE2 for entry; plasma from vaccinated subjects neutralized ancestral virus far better than Omicron, with a 22‑fold reduction in neutralization, yet those with prior infection retained residual Omicron neutralization comparable to ancestral virus in vaccination‑only subjects, indicating that vaccination can still afford reasonable protection against Omicron.

Abstract

The emergence of the SARS-CoV-2 variant of concern Omicron (Pango lineage B.1.1.529), first identified in Botswana and South Africa, may compromise vaccine effectiveness and lead to re-infections1. Here we investigated Omicron escape from neutralization by antibodies from South African individuals vaccinated with Pfizer BNT162b2. We used blood samples taken soon after vaccination from individuals who were vaccinated and previously infected with SARS-CoV-2 or vaccinated with no evidence of previous infection. We isolated and sequence-confirmed live Omicron virus from an infected person and observed that Omicron requires the angiotensin-converting enzyme 2 (ACE2) receptor to infect cells. We compared plasma neutralization of Omicron relative to an ancestral SARS-CoV-2 strain and found that neutralization of ancestral virus was much higher in infected and vaccinated individuals compared with the vaccinated-only participants. However, both groups showed a 22-fold reduction in vaccine-elicited neutralization by the Omicron variant. Participants who were vaccinated and had previously been infected exhibited residual neutralization of Omicron similar to the level of neutralization of the ancestral virus observed in the vaccination-only group. These data support the notion that reasonable protection against Omicron may be maintained using vaccination approaches.