Omicron extensively but incompletely escapes Pfizer BNT162b2 neutralization

Area of Science:

• Virology
• Immunology
• Vaccinology

Background:

• The SARS-CoV-2 Omicron variant (B.1.1.529) emerged with potential to evade vaccine immunity and cause reinfections.
• Antibody neutralization is a key mechanism of vaccine protection against SARS-CoV-2.

Purpose of the Study:

• To investigate the neutralization escape of the Omicron variant by antibodies from individuals vaccinated with Pfizer BNT162b2.
• To compare neutralization efficacy in vaccinated individuals with and without prior SARS-CoV-2 infection.

Main Methods:

• Collected blood samples from vaccinated individuals (with and without prior infection) post-Pfizer BNT162b2 vaccination.
• Isolated and sequence-confirmed live Omicron variant virus.
• Compared plasma neutralization of Omicron against an ancestral SARS-CoV-2 strain.

Main Results:

• A 22-fold reduction in vaccine-elicited neutralization was observed for the Omicron variant in both vaccinated groups.
• Individuals with prior infection and vaccination demonstrated higher neutralization of the ancestral strain compared to vaccinated-only participants.
• Residual neutralization of Omicron in previously infected and vaccinated individuals was comparable to ancestral strain neutralization in vaccinated-only individuals.

Conclusions:

• Vaccination approaches may offer reasonable protection against the Omicron variant.
• Prior infection combined with vaccination may enhance neutralization capacity against SARS-CoV-2 variants.
• Omicron utilizes the ACE2 receptor for cell entry, similar to other SARS-CoV-2 strains.