Immunogenicity and safety of Sinovac-CoronaVac booster vaccinations in 12-17- year-olds with clinically significant reactions from Pfizer-BNT162b2 vaccination.

Heterologous Sinovac-CoronaVac booster(s) in 12-17-year-olds who had a moderate/severe reaction to Pfizer-BNT162b2 mRNA vaccine was found to safe with no serious adverse events reported. In those primed with 1 dose of Pfizer-BNT162b2 vaccine, subsequent boosters with 2 doses of Sinovac-CoronaVac vaccines achieved neutralizing antibody levels which were comparable to those who had received 2 doses of Pfizer-BNT162b2 vaccines followed by 1 dose of Sinovac-CoronaVac vaccination. Adolescents with 1 Pfizer-BNT162b2 followed by 2 Sinovac-CoronaVac vaccines developed T-cell responses against broad peptides including membrane, nucleoprotein 1 and 2 but levels were highest for Spike protein and lasted until day 150 post-vaccination.

Distinctive serotypes of SARS-related coronaviruses defined by convalescent sera from unvaccinated individuals.

Multiple Omicron sub-lineages have emerged, with Omicron XBB and XBB.1.5 subvariants becoming the dominant variants globally at the time of this study. The key feature of new variants is their ability to escape humoral immunity despite the fact that there are limited genetic changes from their preceding variants. This raises the question of whether Omicron should be regarded as a separate serotype from viruses serologically clustered with the ancestral severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. Here, we present cross-neutralization data based on a pseudovirus neutralization test using convalescent sera from naïve individuals who had recovered from primary infection by SARS-CoV-1 and SARS-CoV-2 strains/variants including the ancestral virus and variants Beta, Delta, Omicron BA.1, Omicron BA.2 and Omicron BA.5. The results revealed no significant cross-neutralization in any of the three-way testing for SARS-CoV-1, ancestral SARS-CoV-2 and SARS-CoV-2 Omicron subvariants. The data argue for the assignment of three distinct serotypes for the currently known human-infecting SARS-related coronaviruses.