Background: We carried out a literature search for summarizing currently published evidence on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron (B.1.1.529) variant neutralizing properties of serum or plasma collected from recipients of coronavirus disease 2019 (COVID-19) vaccines.
Methods: An electronic search was conducted in Medline and Scopus, using the keywords “vaccine” AND “Omicron” OR “B.1.1.529” AND “SARS-CoV-2” AND “neutralization” OR “antibodies”, with no language or date limits (i.e., up to December 27, 2021). Studies with complete information on neutralization properties of COVID-19 vaccines against the Omicron variant, with or without the adjunctive effects of booster vaccine doses, were included.
Results: Our final analysis included 10 published studies. In all, decreased neutralisation of SARS-CoV-2 Omicron B.1.1.529 variant was evidenced in post-vaccination samples, ranging between -4.3 folds to absence of neutralization compared to an ancestral SARS-CoV-2 strain. In all studies the COVID-19 vaccine booster dose was effective to elicit sustained enhancement of SARS-CoV-2 Omicron B.1.1.529 neutralisation, with such increase being comprised between 10-42 folds compared to the pre-booster period.
Conclusion: Vaccine boosters seem strongly advisable for limiting the risk of SARS-CoV-2 Omicron (B.1.1.529) breakthrough infections.