COVID-19 Vaccine Does Not Raise Thrombotic Risk in Antiphospholipid Syndrome

blood clot
blood clot
Researchers explored whether inactivated COVID-19 vaccine influences prothrombotic autoantibodies in antiphospholipid syndrome.

The COVID-19 vaccine does not increase the risk for prothrombotic antibody-induced thrombotic events among patients with antiphospholipid syndrome (APS), according to study results published in Rheumatology (Oxford).

Researchers conducted a prospective cohort study that comprised 39 patients with APS (median age 38 years; 82.1% [n=32] women) who received 2 COVID-19 vaccine doses 21 days apart. Recruitment took place between January 3, 2022, and February 6, 2022. Follow-up lasted a minimum of 12 weeks. The determination of 11 prothrombotic autoantibodies was conducted both 7 days before the first vaccine dose and 4 weeks after the second dose. Thrombotic disorders were assessed during hospital visits.

There was no significant positivity difference in patients 7 days before receiving the first dose vs 4 weeks after receiving the second dose of COVID-19 vaccine for anticardiolipin, immunoglobulin (Ig) G, IgM and IgA; anti-β2GP1, IgG, IgM and IgA; antihosphatidylserine/prothrombin, IgG and IgM; lupus anticoagulation; aPF4-heparin; and antinuclear antibodies.

The vaccine did not affect the distribution of antiphospholipid antibodies (aPLs) in either those with low-risk (11 vs 10 [prevaccine vs postvaccine, respectively]; P =.799) or high-risk (28 vs 29; P =.799) aPL profiles. No cases of thrombotic disorders occurred during the 12-week follow-up period, and treatment regimens were not adjusted after vaccination.

Limitations to this study include a small sample size and a lack of longer-term follow-up.

The study authors conclude. “[T]he inactivated vaccine does not increase the risk [for] prothrombotic antibody-induced thrombotic events in the context of immune system disorders.” They indicated that this “provides evidence to rheumatologists to make interest-based vaccination guidance for [patients with] APS.”


Pan H, Tang Z, Teng J, et al. COVID-19 vaccine affects neither prothrombotic antibody profile nor thrombosis in primary antiphospholipid syndrome: a prospective study. Rheumatology (Oxford). Published online July 22, 2022. doi: 10.1093/rheumatology/keac400