Vaccines against SARS-CoV-2 have been recommended across the world, yet no study has investigated whether COVID-19 vaccination influences short-term warfarin anti-coagulation levels. Patients on stable warfarin treatment who received anti-SARS-CoV-2 vaccination were prospectively enrolled and followed up for three months. INR values less than 10 days before vaccination (baseline), 3–5 days (short-term) and 6–14 days (medium-term) after vaccination were recorded as INR0, INR1, and INR2, respectively. The variations of INR values within individuals were compared, and the linear mixed effect model was used to evaluate the variations of INR values at different time points. Logistic regression analysis was performed to determine covariates related to INR variations after COVID-19 vaccination. Vaccination safety was also monitored. There was a significant difference in INR values between INR0 and INR1 (2.15 vs. 2.26, p = 0.003), yet no marked difference was found between INR0 and INR2. The linear mixed effect model also demonstrated that INR variation was significant in short-term but not in medium-term or long-term period after vaccination. Logistic regression analysis showed that no investigated covariates, including age, vaccine dose, genetic polymorphisms of VKORC1 and CYP2C9 etc., were associated with short-term INR variations. Two patients (2.11%) reported gingival hemorrhage in the short-term due to increased INR values. The overall safety of COVID-19 vaccines for patients on warfarin was satisfying. COVID-19 vaccines may significantly influence warfarin anticoagulation levels 3–5 days after vaccination. We recommend patients on warfarin to perform at least one INR monitoring within the first week after COVID-19 vaccination.

世界各地已推荐针对 SARS-CoV-2 的疫苗，但尚无研究调查 COVID-19 疫苗接种是否会影响短期华法林抗凝水平。前瞻性入组接受稳定华法林治疗并接受抗 SARS-CoV-2 疫苗接种的患者并随访三个月。接种前10天（基线）、接种后3-5天（短期）和6-14天（中期）的INR值分别记录为INR0、INR1和INR2。比较个体内INR值的变化，并采用线性混合效应模型评估不同时间点INR值的变化。进行逻辑回归分析以确定与 COVID-19 疫苗接种后 INR 变化相关的协变量。还监测了疫苗接种的安全性。 INR0 和 INR1 之间的 INR 值存在显着差异（2.15 与 2.26，p  = 0.003），但 INR0 和 INR2 之间没有发现显着差异。线性混合效应模型还表明，INR 变化在疫苗接种后的短期内显着，但在中长期内不显着。 Logistic回归分析显示，年龄、疫苗剂量、VKORC1和CYP2C9基因多态性等研究的协变量与短期INR变化无关。两名患者（2.11%）报告因INR值升高而导致短期牙龈出血。对于服用华法林的患者来说，COVID-19 疫苗的总体安全性令人满意。 COVID-19 疫苗可能会在接种疫苗后 3-5 天显着影响华法林抗凝水平。我们建议服用华法林的患者在接种 COVID-19 疫苗后第一周内至少进行一次 INR 监测。