W75 - A 10-Month Period Evaluation of Cellular Responses After ChAdOx1-nCoV-19 and BNT162b2 Vaccinations

Background

Since the outbreak of COVID-19, vaccines against SARS-CoV-2 were developed. While many studies evaluated the humoral responses to the vaccinations, data on cellular responses are sparse. We evaluated T-cell responses after ChAdOx1-nCoV-19 and BNT162b2 during 10 months.

Methods

From March to December 2021, interferon (IFN)-gamma was measured with Covi-FERON ELISA (SD Biosensor Inc., Suwon, South Korea) in blood samples from 91 individuals. For the ChAdOx1-nCoV-19-vaccinated group (N=36), three weeks/three months/five months after the second dose and three weeks after the BNT162b2 booster dose were measured. For the BNT162b2-vaccinated group (N=30), three months/six months after the second dose and three weeks after the booster dose were measured. Control group (N=25) consisting of unvaccinated individuals without history of COVID-19 infection and negative for SARS-CoV-2 anti-nucleocapsid IgG was also included.

Results

The median (IQR) IFN-gamma value (IU/mL) of the control group was -0.01 (-0.03–0.00). In ChAdOx1-nCoV-19, medians were 0.31 (0.12–0.69), 0.14 (0.04–0.24), 0.14 (0.06–0.41), and 1.92 (0.73–5.01) for three weeks, three months, five months, and three weeks after booster, respectively. In BNT162b2, medians were 0.54 (0.36–1.01), 0.31 (0.16–0.86), and 1.93 (1.13–4.00) for three months and six months after the second dose, and three weeks after booster, respectively.

Conclusions

Both ChAdOx1-nCoV-19- and BNT162b2-vaccinated group showed high T-cell responses in contrast to unvaccinated group. The responses were declined afterwards but were highly increased after booster. This could be a baseline data on T-cell responses after SARS-CoV-2 vaccination and IFN-gamma assay would be useful in monitoring immunogenicity in vaccinated population.