Third dose of BNT162b2 may protect against Omicron, study shows

A new study that evaluated the effectiveness of the BNT162b2 (Pfizer-BioNTech) vaccine against the Omicron variant indicates that three doses could offer a sufficient level of protection from disease caused by the Omicron variant. The globally circulating SARS-CoV-2 Variant of Concern (VOC) Omicron (B.1.1.529) has a large number of mutations, especially in the spike protein, indicating that recognition by neutralizing antibodies may be compromised. Alexander Muik and colleagues tested Wuhan, Beta, Delta, or Omicron pseudoviruses with sera of 51 participants that received two or three doses of the mRNA-based COVID-19 vaccine BNT162b2. Following two doses, sera had more than 22-fold reduced neutralizing titers against Omicron compared to Wuhan pseudovirus. One month after the third vaccine dose, Omicron-neutralizing titers were increased 23-fold compared to two doses, with titers similar to Wuhan-neutralizing titers after two doses. The data suggest “a third dose of BNT162b2 augments antibody-based immunity against Omicron, in line with previous observations that a third vaccination broadens humoral immune responses against VOCs,” say the authors. “Further clinical trial and real-world data will soon emerge to address the effectiveness of a third dose with BNT162b2 against COVID-19 mediated by Omicron,” they conclude.