Superficial venous thrombosis as a possible consequence of ChAdOx1 nCoV-19 vaccine: two case reports

Background: Many scientists across the world got involved in the race to develop successful anti-SARS-CoV-2 vaccines to overcome COVID-19 pandemic. Among the different vaccines developed against SARS-CoV-2, Covishield was the first vaccine approved for emergency use in Nepal. We report two cases of Superficial Vein Thrombosis (SVT) for the first time in the literature after vaccination with the Chimpanzee Adenovirus-vectored Vaccine (ChAdOx1 nCoV-19 vaccine). Cases presentation: Two cases, a 24-year-old young Chhetri male and a 62-year-old Chhetri female who have received Covishield (ChAdOx1 nCoV-19) vaccine, developed pain in left calf after 2 weeks and 10 weeks of vaccination, respectively. Both the case belongs to the Chhetri ethnic group of Nepal. The pain became severe on the fourth week of immunization in the first case while the pain was acute and severe on the 10 th week of vaccination in the second case. The first presented to emergency room and second case was referred to the emergency room from Orthopedic Clinic. On evaluation the first patient had normal vitals with no history of fever and swelling yet displayed non-radiating mild to moderate intensity pain localized to left leg below the knee which became aggravated by movements. In the second case however pain was more intense with other characteristics as first case. Both cases had low wells score (< 4). On local examination tenderness was noted on squeezing but other systemic examination findings of the patient were within normal limits in both cases. Among the numerous vaccines used to fight the battle against COVID-19 disease, delayed thromboses in superficial vein have been reported after vaccination of ChAdOx1 nCoV-19 vaccine and they may be the consequences of vaccination though larger study is needed to verify them. 3. Superficial vein thrombosis (SVT) should be an additional adverse effect to be mentioned in the list of adverse events associated with ChAdOx1 nCoV-19, Covishield, vaccine. 4. The benefits of the vaccine in breaking the chain of COVID 19 spread are certainly greater than the risk of thromboses.