The immediate effect of COVID-19 vaccination on anticoagulation control in adolescents and young adults using vitamin K antagonists

ABSTRACT

Background: The European Medicine Agency has authorized COVID-19 vaccination in young adults from 12 years onwards. COVID-19 vaccination is associated with a negative effect on the quality of anticoagulation stability in adult vitamin K antagonists (VKA) users, due to an increased risk of supra-and subtherapeutic INRs after the first vaccination. It is unknown whether this effect is also observed in adolescents and young adults (AYA) using VKAs. Aim(s) To investigate whether the COVID-19 vaccine also affects anticoagulation stability in AYAs using VKA. Method(s) A case-crossover study was performed in a cohort of AYAs (12-30 years) using VKA. INR results before vaccination, the reference period, were compared with the first INR after the first and, if applicable, second vaccination. Vaccination is deemed safe when the INR is <3.5. Anticoagulation clinics were encouraged to measure the INR within 2 weeks after vaccination. Result(s) Ninety-six AYAs were included, with a median age [IQR] of 25 [7] years, of whom 53.1% were female and 67.7% used acenocoumarol. The majority of AYAs (69.8%) received the BNT162b2 vaccine. [Table 1]. The percentage of INR results within range was significantly lower after the first vaccination (60/97 (62.5%) vs. 40/97 (41.7%), p = 0.004) due to an increase in supratherapeutic INRs (12/97 (12.5%) vs. 30/97 (31.3%), p = 0.005) [Figure 1]. The percentages of subtherapeutic INRs (24/97 (25.0%) vs. 26/97 (27.1%), p = 0.864) and INRs >=5 (1/97 (1.0%) vs. 2/97 (2.1%), p = 1.000) before and after first vaccination were similar. No differences were observed after the second vaccination compared to before or after the first vaccination. Complications after vaccination occurred less often than before vaccination (3.0 vs. 20.0, p = 0.012) and were non-severe. Conclusion(s) COVID-19 vaccination is also associated with a negative effect on anticoagulation stability in AYA VKA users, but not with an increase in complications. Still, it is advisable to monitor the INR shortly after vaccination.