Abstract
Patients with protein S (PS) deficiency possibly have a higher risk of developing severe COVID-19 disease. Therefore, vaccination against SARS-CoV-2 infections is recommended for PS-deficient patients. However, there are limited data regarding the safety and immunogenicity of the currently available COVID-19 mRNA vaccine in PS-deficient patients. We report a case of monitoring the antibody response of a 40-year-old female diagnosed with PS deficiency and on warfarin treatment following a single dose of BNT162b2 mRNA vaccine. Antibody against the receptor-binding domain (RBD) of the SARS-CoV-2 spike (S) protein (anti-S) was measured on days 7, 14, and 21 after vaccination. Seroconversion was detected on day 21 but was possibly lower than the anti-S level previously reported in healthy individuals after receiving the first dose of the BNT162b2 mRNA vaccine. There were no local and systemic events reported up to 7 days in this patient after vaccination. This case highlights that the administration of the BNT162b2 vaccine had a favourable safety profile, and the second dose of the vaccine is required to provide the optimal protection against SARS-CoV-2 infection in PS-deficient patients.