Dynamics of Lymphocyte Subsets During the Covid-19 Vaccination Process in Japanese General Population

BackgroundThe effectiveness of COVID-19 vaccination in preventing SARS-CoV-2 infection and severe disease has been confirmed in Japan. However, individual differences and dynamics changes of lymphocyte subsets over several months in the assessment of cellular immunity are not fully understood.MethodsThis prospective study included 29 participants from the general population in Japan and used the COVID-19 mRNA vaccine. Participants were vaccinated with the second dose at least three weeks after the first dose and the third dose eight months after the second dose. Blood samples were taken at baseline and at approximately the following times: 3 weeks after the first dose; 1 month, 3 months and 6 months after the second dose; and 1 month and 6 months after the third dose. The blood cells were stained with BD Multites 6-colour TBNK within 12 hours after blood collection and lymphocyte subsets were analyzed by flow cytometer.ResultThe mean B-cell count showed a decreasing trend at 3 weeks after the first vaccination and increased 1 month after the second vaccination. The mean CD8+ T-cell count showed a decreasing trend until 3 months after the second vaccination and turned to an increasing trend from 6 months after. The mean CD4+ T-cell count showed an increasing trend at 3 weeks after the first vaccination, but no significant changes were observed. For the individual level, the lymphocyte subset cell counts at each time point ranged from 70 to 600 cells/μl for B cells, 100 to 1000 cells/μl for CD8+ T cells, and 200 to 1300 cells/μl for CD4+ T cells, with large individual differences and dynamics changes.ConclusionWhen assessing cellular immunity after COVID-19 vaccination, it might be important to consider individual differences and dynamics changes of lymphocyte subsets.