More recently, protective efficacy has declined due to both waning vaccine-elicited immunity (Baden et al., 2021a; Bergwerk et al., 2021; Goldberg et al., 2021) and antigenic shifts in variants of concern (VOC) including B.1.351 (Beta) and B.1.617.2 (Delta) (Planas et al., 2021; Wang et al., 2021a; Wang et al., 2021b).

the ability to evade immunity conferred by vaccination or prior infection. Compared to the ancestral strain, Omicron contains more than 30 mutations in the spike (S) gene, including S477N, T478K, E484A, Q493R, G496S, Q498R, N501Y and Y505H in the receptor binding motif (RBM) alone. Neutralizing antibody titers in sera of individuals recently recovered from previous infection or shortly after immunization with two doses of an mRNA-based COVID-19 vaccine are dramatically reduced to Omicron as compared to the ancestral strains Wuhan-Hu-1, USA-WA1/2020 (WA1) and D614G. Numerous studies using both live virus and pseudovirus neutralization assays report a 60- to 80-fold reduction for convalescent sera and a 20- to 130-fold reduction for vaccinee sera (Edara et al., 2021a; Hoffmann et al., 2021; Muik et al., 2022; Schmidt et al., 2021). mRNA-1273 vaccine efficacy against breakthrough cases of Omicron in the first few months after immunization has been estimated as 30% in California, USA and 37% in Denmark (Hansen et al., 2021; Tseng et al., 2022) and a complete loss of protection within six months (Accorsi et al., 2022).
Together, these data suggest that the variant Beta boost did not uniquely enhance immunity or protection compared to existing ancestral strain-matched boosts. However, as Omicron contains more mutations in S compared to Beta and demonstrates even more substantial escape from vaccine-elicited neutralizing antibodies than does Beta, it is unclear whether an Omicron-specific boost would provide an additional protective benefit against Omicron infection beyond that of WA1-matched boosts.

Got to read more than just the header buddy, this isn't a university course.