Monitoring of adaptive immune responses in healthcare workers who received a Coronavirus disease 2019 vaccine booster dose

Abstract

AbstractBackground and AimsCoronavirus disease 2019 (COVID‐19) has become a global pandemic and led to increased mortality and morbidity. Vaccines against the etiologic agent; severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) were approved for emergency use on different platforms. In the early phase of the pandemic, Thai healthcare workers (HCWs) received CoronaVac, an inactivated vaccine, as the first vaccine against SARS‐CoV‐2, followed by ChAdOx1 nCoV‐19, a viral vector‐based vaccine, or BNT162b2, an mRNA vaccine, as a booster dose. This preliminary study evaluated the immunogenicity of ChAdOx1 nCoV‐19 and BNT162b2 as a booster dose in HCWs who previously received two doses of CoronaVac.MethodsTen HCW participants received ChAdOx1 nCoV‐19 and another 10 HCWs received BNT162b2 as a booster dose after two doses of CoronaVac. Anti‐RBD IgG, neutralizing antibodies (NAb), and cellular immunity, including interferon‐gamma (IFN‐γ)‐releasing CD4, CD8, double negative T cells, and NK cells, were measured at 3 and 5 months after the booster dose.ResultsThere was no significant difference in anti‐RBD IgG levels at 3 and 5 months between the two different types of booster vaccine. The levels of anti‐RBD IgG and NAb were significantly decreased at 5 months. HCWs receiving BNT162b2 had significantly higher NAb levels than those receiving ChAdOx1 nCoV‐19 at 5 months after the booster dose. IFN‐γ release from CD4 T cells was detected at 3 months with no significant difference between the two types of booster vaccines. However, IFN‐γ‐releasing CD4 T cells were present at 5 months in the ChAdOx1 nCoV‐19 group only.ConclusionChAdOx1 nCoV‐19 or BNT162b2 can be used as a booster dose after completion of the primary series primed by inactivated vaccine. Although the levels of immunity decline at 5 months, they may be adequate during the first 3 months after the booster dose.