ABSTRACT
This study compared the humoral immune characteristics of children, elderly people, pregnant women, and adults infected with BA.5 and XBB strains in Guangzhou, China. It was found that binding and neutralizing antibodies the titers against distinct SARS-CoV-2 strains were low in the acute-phase sera of BA.5 infected patients, while the corresponding titers were significantly increased in the convalescent phase, the antibody titers against the Wuhan strain were the highest. Regardless of whether they were vaccinated, BA.5 infection did not induce high neutralizing antibodies against XBB. During the recovery phase, the titers of antiviral antibodies in the vaccinated population are more robust than those in the unvaccinated population. For BA.5 infections, the specific binding and neutralizing antibody titers in the children group were lower compared to other population groups. In the convalescence period of the disease, the titers of neutralizing antibodies against Wuhan, BA.5 and XBB strains induced by BA.5 infections are significantly correlated in pairs. XBB can induce a broader and balanced antiviral humoral immune response than BA.5 as a first-time infected strain. This finding can provide a reference for the judgment of the future epidemic law of SARS-CoV-2, and provide a scientific basis for developing novel COVID-19 vaccines, especially for discovering customized vaccines and immune strategies for different populations.