Enhanced RBD-Specific Antibody Responses and SARS-CoV-2-Relevant T-Cell Activity in Healthcare Workers Following Booster Vaccination.

COVID-19 continues to impact healthcare workers (HCWs), making it crucial to investigate vaccine response rates. This study examined HCWs' humoral and cellular immunological responses to COVID-19 booster dosages. We enrolled thirty-four vaccinated HCWs. Twelve received a booster. Post-immunization, the participants' anti-COVID-19 IgG antibodies and IFN-γ secretion were assessed. The median second immunization response time was 406.5 days. Eighteen of twenty-two (81.8%) experienced breakthrough infections after the second vaccination, whereas ten out of twelve individuals who received booster doses had breakthrough infections (83.3%). Six of thirty-four HCWs (17.6%) had no breakthrough infections. Booster-injection recipients had a median antibody titer of 19,592 AU/mL, compared to 7513.55 AU/mL. HCWs with breakthrough infections exhibited a median antibody titer of 13,271.9 AU/mL, compared to 7770.65 AU/mL for those without infections. Breakthrough-infection and booster-injection groups had a slightly higher median T-cell response to antigens 1, 2, and 3. SARS-CoV-2 antibody titer and T-cell responsiveness were positively associated. HCWs sustain cellular and humoral immunity for over 10 months. Irrespective of the type of vaccine, booster injections enhance these immune responses. The results of our research are consistent with previous studies, and a multicenter investigation could validate the findings.