Improved Neutralisation of the SARS-CoV-2 Omicron Variant following a Booster Dose of Pfizer-BioNTech (BNT162b2) COVID-19 Vaccine

In late November 2021, the World Health Organization declared the SARS-CoV-2 lineage B.1.1.529 the fifth variant of concern, Omicron. This variant has acquired over 30 mutations in the spike protein (with 15 in the receptor-binding domain), raising concerns that Omicron could evade naturally acquired and vaccine-derived immunity. We utilized an authentic virus, multicycle neutralisation assay to demonstrate that sera collected one, three, and six months post-two doses of Pfizer-BioNTech BNT162b2 had a limited ability to neutralise SARS-CoV-2. However, four weeks after a third dose, neutralising antibody titres were boosted. Despite this increase, neutralising antibody titres were reduced fourfold for Omicron compared to lineage A.2.2 SARS-CoV-2.

Automated summary

The Omicron variant of SARS-CoV-2, declared as the fifth variant of concern by the World Health Organization, has multiple spike protein mutations that raise concerns about immune evasion. Research shows that sera from individuals who received two doses of the Pfizer-BioNTech BNT162b2 vaccine have limited neutralizing ability against SARS-CoV-2, but a third dose can boost neutralizing antibody titres. However, even with the boost, neutralizing antibody titres for Omicron are four times lower compared to the A.2.2 lineage of SARS-CoV-2.