evidence: HCoVs have been circulating in the population for decades, and no licensed CoV vaccine was available until December 2020 as a direct consequence of the COVID-19 pandemic. Before the pandemic, a few vaccine candidates against MERS-CoV, MVA-MERS-S, GLS-5300 DNA, and ChAdOx1-MERS were tested in phase I clinical trials82,83,84,85,86. Nevertheless, none were entered into phase II or III trials and approved for human use by the US FDA (United States Food and Drug Administration). [...] Since developing a vaccine that protects against all CoVs is likely difficult to achieve due to its genetic variability, as discussed above, a tiered approach likely has a higher chance of success, beginning with COVID-19 vaccines, which can protect against all VOCs, to pan-sarbecovirus vaccines, to pan-betacoronavirus vaccines, to universal or pan-coronavirus vaccines139. Both Pfizer and Moderna have developed bivalent vaccines targeting ancestral SARS-CoV-2 and Omicron. Compared to the monovalent booster, these second-generation vaccines have moderately higher or similar effectiveness in inducing neutralizing antibody responses against Omicron variants in vaccinated infection-naïve cohorts140,141,142. However, immune imprinting and the antigenic variation within Omicron limit the induction of neutralizing antibody responses against newer variants143,144,145,146,147. A recent study carried out on serum samples obtained from participants who had received one or two monovalent boosters or the mRNA bivalent booster indicated that the neutralizing antibody responses are lower against BA.1, BA.5, BA.2.75.2, BQ.1.1, and XBB as that of the ancestral strain WA1 in all three cohorts148.