Professor Hallym University Dongtan Sacred Heart Hospital Seoul, Kyonggi-do, Republic of Korea
Abstract Text:
Background: We performed quantitative analysis of SARS-CoV-2 antibodies after completing two doses of AstraZeneca (AZ) ChAdOx1 nCoV-19 vaccine and a booster dose of Pfizer BNT162b2 vaccine (Pfizer).
Methods: A total of 160 serum samples were obtained from 80 healthcare workers 4 weeks and 4 months after a three-dose AZ-AZ-Pfizer vaccination. Twenty-seven (33.7%) of 80 participants experienced COVID-19 infection during this 4-month study period, and participants in the infected group stated that infection occurred 8 to 37 days before the second blood draw. Total antibody titers against the spike protein (anti-S) and nucleocapsid protein (anti-N) of SARS-CoV-2 were measured using the Elecsys anti-SARS-CoV-2 S and Elecsys anti-SARS-CoV-2 assays (Roche), respectively.
Results: The median anti-S antibody titer at 4 months after the 3rd dose were significantly decreased in both the infected groups and non-infected groups compared with those after 4 weeks, and the infected group showed significantly higher antibody titers than the non-infected group (Infected group: from 21,178 to 18,108 U/mL vs. non-infected group: from 17,777 to 3,068 U/mL). The median titer of anti-N antibody titer at 4 months after the 3rd dose was 2.21 cut-off index (COI) (range: 0.186–37.4, 74.1% positivity) in the infected group.
Conclusions: After a three-dose AZ-AZ-Pfizer vaccination, the median anti-S antibody titers decreased in both the infected and non-infected groups 4 months after the 3rd dose compared with those of 4 weeks after the 3rd dose. These data will provide useful information for determining quarantine strategies including the fourth vaccination.
