Effectiveness of COVID-19 vaccination in healthcare workers in Shiga Prefecture, Japan

• Published in: Scientific reports Vol. 12; no. 1; pp. 17621 - 9
• Main Authors: Chano, Tokuhiro, Yamashita, Tomoko, Fujimura, Hirokazu, Kita, Hiroko, Ikemoto, Toshiyuki, Kume, Shinji, Morita, Shin-ya, Suzuki, Tomoyuki, Kakuno, Fumihiko
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 21.10.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 631/250/255/2514; 692/699/255/2514; Cell-mediated immunity; Coronaviruses; COVID-19; COVID-19 - epidemiology; COVID-19 - prevention & control; COVID-19 Vaccines; Health care; Health Personnel; Humanities and Social Sciences; Humans; Immune response (humoral); Immunoglobulin G; Immunoglobulin M; Japan - epidemiology; Medical personnel; multidisciplinary; SARS-CoV-2; Science; Science (multidisciplinary); Serology; Severe acute respiratory syndrome coronavirus 2; Vaccination; Japan
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-022-22682-3

This study, which included serological and cellular immunity tests, evaluated whether coronavirus disease 2019 (COVID-19) vaccination adequately protected healthcare workers (HCWs) from COVID-19. Serological investigations were conducted among 1600 HCWs (mean ± standard deviation, 7.4 ± 1.4 months after the last COVID-19 vaccination). Anti-SARS-CoV-2 antibodies N-Ig, Spike-Ig (Roche), N-IgG, Spike-IgM, and -IgG (Abbott), were evaluated using a questionnaire of health condition. 161 HCWs were analyzed for cellular immunity using T-SPOT ® SARS-CoV-2 kit before, and 52 HCWs were followed up until 138.3 ± 15.7 days after their third vaccination. Spike-IgG value was 954.4 ± 2282.6 AU/mL. Forty-nine of the 1600 HCWs (3.06%) had pre-existing SARS-CoV-2 infection. None of the infectious seropositive HCWs required hospitalization. T-SPOT value was 85.0 ± 84.2 SFU/10 6 cells before the third vaccination, which increased to 219.4 ± 230.4 SFU/10 6 cells immediately after, but attenuated later (to 111.1 ± 133.6 SFU/10 6 cells). Poor counts (< 40 SFU/10 6 cells) were present in 34.8% and 38.5% of HCWs before and after the third vaccination, respectively. Our findings provide insights into humoral and cellular immune responses to repeated COVID-19 vaccinations. COVID-19 vaccination was effective in protecting HCWs from serious illness during the original Wuhan-1, Alpha, Delta and also ongoing Omicron-predominance periods. However, repeated vaccinations using current vaccine versions may not induce sufficient cellular immunity in all HCWs.