Elsevier established a free COVID-19 resource center in January 2020, offering information on the novel coronavirus in English and Mandarin. The center is hosted on Elsevier Connect, a public news and information website. Elsevier grants permission to make all its COVID-19-related research freely available in PubMed Central and other public repositories for unrestricted research use. A study shows that mRNA-based COVID-19 vaccine boosters induce neutralizing immunity against the SARS-CoV-2 Omicron variant. The Omicron variant has 34 mutations in the spike protein, more than other variants. Two doses of mRNA vaccines elicit poor neutralization of Omicron, but three doses elicit potent cross-neutralization, including against Omicron. The Omicron pseudovirus infects cells more efficiently than other variants. The study involved 239 vaccinees who had received one of three approved vaccines in the U.S. - mRNA-1273, BNT162b, or Ad26.COV2.S. Sera from these individuals were tested against wild-type, Delta, and Omicron pseudoviruses. Neutralization of Omicron was undetectable in most vaccinees, but individuals boosted with mRNA vaccines showed potent neutralization of Omicron, only 4-6-fold lower than wild type. Omicron pseudovirus infects target cells more efficiently than other variants. The study highlights the importance of additional mRNA doses to broaden neutralizing antibody responses against highly divergent SARS-CoV-2 variants. The Omicron variant evades vaccine-induced neutralizing immunity under current vaccine regimens and is more infectious than previous variants. However, individuals who received a third dose of mRNA vaccine showed potent cross-neutralizing immunity against Omicron, suggesting that existing vaccines may overcome evasion of humoral immunity by future variants. The study also found that Omicron retains ACE2 usage and exhibits higher infection rates than other SARS-CoV-2 variants in vitro. The results suggest that Omicron drastically escapes vaccine-induced immunity after primary vaccination series with mRNA vaccines and exhibits increased pseudovirus infection rates in vitro, raising the potential for increased transmissibility. The study supports the need for rapid and synchronized widespread deployment of additional mRNA vaccine doses as a public health measure to curtail the emergence and spread of highly mutated SARS-CoV-2 variants.Elsevier established a free COVID-19 resource center in January 2020, offering information on the novel coronavirus in English and Mandarin. The center is hosted on Elsevier Connect, a public news and information website. Elsevier grants permission to make all its COVID-19-related research freely available in PubMed Central and other public repositories for unrestricted research use. A study shows that mRNA-based COVID-19 vaccine boosters induce neutralizing immunity against the SARS-CoV-2 Omicron variant. The Omicron variant has 34 mutations in the spike protein, more than other variants. Two doses of mRNA vaccines elicit poor neutralization of Omicron, but three doses elicit potent cross-neutralization, including against Omicron. The Omicron pseudovirus infects cells more efficiently than other variants. The study involved 239 vaccinees who had received one of three approved vaccines in the U.S. - mRNA-1273, BNT162b, or Ad26.COV2.S. Sera from these individuals were tested against wild-type, Delta, and Omicron pseudoviruses. Neutralization of Omicron was undetectable in most vaccinees, but individuals boosted with mRNA vaccines showed potent neutralization of Omicron, only 4-6-fold lower than wild type. Omicron pseudovirus infects target cells more efficiently than other variants. The study highlights the importance of additional mRNA doses to broaden neutralizing antibody responses against highly divergent SARS-CoV-2 variants. The Omicron variant evades vaccine-induced neutralizing immunity under current vaccine regimens and is more infectious than previous variants. However, individuals who received a third dose of mRNA vaccine showed potent cross-neutralizing immunity against Omicron, suggesting that existing vaccines may overcome evasion of humoral immunity by future variants. The study also found that Omicron retains ACE2 usage and exhibits higher infection rates than other SARS-CoV-2 variants in vitro. The results suggest that Omicron drastically escapes vaccine-induced immunity after primary vaccination series with mRNA vaccines and exhibits increased pseudovirus infection rates in vitro, raising the potential for increased transmissibility. The study supports the need for rapid and synchronized widespread deployment of additional mRNA vaccine doses as a public health measure to curtail the emergence and spread of highly mutated SARS-CoV-2 variants.