Coronavirus disease 19 (COVID-19) has an increased risk of coagulopathy, especially the occurrence of thromboembolic events. The intense inflammatory response evoked by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) replication may induce a dysregulation of coagulation towards a hypercoagulable state1,2,3, and both large vessels and microcirculation may be affected4. In fact, a recent systematic review and meta-analysis, including mainly hospitalized patients with COVID-19, demonstrated rates of pulmonary embolism (PE) and deep vein thrombosis (DVT) of 16.5% and 14.8%, respectively. Of those, more than half of patients with PE lacked DVT, and the prevalence of thrombosis increased with severity (up to 24.7% of PE in critically ill patients)5. Rates of arterial thrombotic events are also increased, with an overall prevalence of 4%6.
Different factors have been associated with the genesis of this prothrombotic state in COVID-19, such as oxidative stress damage, endothelial dysfunction, von Willebrand factor and the complement pathway activation and production of neutrophil extracellular traps (NETs)7. Still, angiotensin converting enzyme 2 (ACE2) downregulation results in renin-angiotensin-aldosterone system augmentation, which clearly contributes to the thromboembolic events in COVID-19 patients7. Antiphospholipid syndrome (APS) is the most frequent acquired thrombophilia8. Half of the cases, known as primary APS (PAPS), occurs without the concomitance of other autoimmune rheumatic diseases (ARD)9. APS is characterized by the persistent presence of antiphospholipid antibodies (aPL), namely lupus anticoagulant (LA), IgG and/or IgM anticardiolipin (aCL) and IgG and/or IgM anti-beta-2 glycoprotein I (aβ2GPI), which play an important role in the pathogenesis of thrombosis in those patients10. Recent studies, including a meta-analysis and systematic review, reported the presence of aPL in patients infected with SARS-CoV-2, and this may be an additional factor increasing the risk of thrombosis in this context11,12,13,14. Furthermore, all the aforementioned mechanisms of COVID-19 may act as the ‘second hit’, crucial for the thrombogenesis in APS and/or aPL-positive patients11,15,16. In light of that, it is of concern that APS patients may present with a more severe phenotype of COVID-19, with an increased risk of thrombotic events. Therefore, vaccinating these patients to prevent this infectious disease is of utmost importance.
Paradoxically, two of the vaccines against SARS-CoV-2 using adenovirus platforms developed by AstraZeneca and Janssen have been associated with the occurrence of rare and atypical thromboembolic events, especially in women under 50 years of age, a condition that has been called vaccine-induced immune thrombotic thrombocytopenia (VITT)17. As a consequence, vaccinating patients with APS and other thrombophilias using other platforms, such as inactivated virus or mRNA, may be preferable in this subset of patients. However, studies on the efficacy and safety of those vaccines in APS are still lacking.
CoronaVac (Sinovac Life Sciences, Beijing, China) is an inactivated vaccine against COVID-19, which is supporting vaccination campaigns in more than 40 countries, including Brazil, and has shown good tolerance and efficacy in inducing humoral responses against SARS-CoV-2 in the general population18,19,20. Jara et al. demonstrated that Sinovac-Coronavac reduced rates of infection, hospitalization, ICU admission and death by 65.9%, 87.5%, 90.3% and 86.3%, respectively, in the overall population of 10.2 million people in Chile21.
Recently, our group reported a phase 4 prospective controlled study including 910 naïve ARD patients that received two doses of Sinovac-Coronavac. A moderate seroconversion rate (70.4%) but lower than the controls (95.5%) was evidenced in ARD patients22. However, PAPS patients have some distinct clinical and immunological features23 compared to other ARDs. In fact, the H1N1 vaccine response in this population was higher than several other ARDs in a study of 1668 patients evaluated by our group24. The specific analysis of immunogenicity and safety in PAPS patents is therefore necessary and particularly the prospective evaluation of the possible change in aPL antibody production.
Thus, the aims of the present prospective study were to evaluate immunogenicity of Sinovac-CoronaVac vaccine in naïve PAPS patients compared to a balanced age- and sex-control group (CG). We further assessed safety, including thrombotic events, and the possible vaccine induced aPL production throughout the study period.