Deep vein thrombosis more than two weeks after vaccination against COVID-19

Patient 1

The patient was a female doctor in her thirties. Aside from hypothyreosis following Hashimoto's thyroiditis in childhood and some lumbago issues, she had been otherwise healthy. She had no history of blood clots, including in connection with pregnancy and childbirth. She was treated with 150 µg of levothyroxine (Levaxin) daily.

The patient was given the ChAdOx1 nCoV-19 vaccine from AstraZeneca. The next night she woke up with intense back pain, and developed a fever and chills. These symptoms resolved within 36 hours.

Sixteen days after vaccination, she developed petechiae in two fingers. The Norwegian Medicines Agency had advised the public to seek urgent medical assistance if they developed symptoms within 14 days of vaccination (1), but as 16 days had now passed and the woman's general health was good, she did not see a doctor or have any tests.

After a few skiing trips, however, three of her toenails turned blue and bruises appeared elsewhere on her body despite not experiencing any impact blows.

Twenty-seven days after vaccination, she awoke with pain in her right popliteal fossa and upper leg without prior trauma. She attributed the symptoms to a busy weekend shift at the hospital. The next day, the pain worsened. A routine hypothyreosis check-up to measure her thyroid hormones was supplemented with further analyses. Blood tests showed haemoglobin 12.7 g/dL (reference range 11.7–15.3), leukocytes 5.5 × 10⁹/L (3.5–10.0), platelets 334 × 10⁹/L (145–390) and D-dimer <0.4 mg/L (< 0.5). She used a simplified Wells score, which showed 0, and concluded that deep vein thrombosis was unlikely.

The next day, she still had severe pain in her popliteal fossa and upper leg, and asked a colleague in the Department of Radiology to carry out an ultrasound examination to rule out deep vein thrombosis. Thrombus was then revealed in the distal popliteal vein (Figure 1).

She was treated with rivaroxaban for three months, 15 mg × 2 for three weeks, followed by 20 mg × 1. One week after confirmation of deep vein thrombosis and initiation of anticoagulant therapy, a head MRI was taken and platelet antibodies were measured in connection with a survey of adverse effects of vaccines. Both examinations revealed no pathological findings. The case was reported as an adverse effect in the registration system for healthcare workers, Melde.no.

Patient 2

The patient was a previously healthy male doctor in his forties who did not use regular medication. Ten hours after vaccination with ChAdOx1 nCoV-19, he developed a brief fever and chills, but continued to feel unwell the next day. Over the next 3–4 days, he experienced joint pain and exhaustion. Light exertion also triggered dyspnoea, which lasted approximately one week.

Ten days after vaccination, he felt slight proximal discomfort in his left lower leg. He interpreted this as a muscular issue, alternatively a Baker's cyst. The symptoms gradually intensified, and after 16 days he observed a slight swelling. However, this receded after a few days. Twenty-four days after vaccination, he took blood tests because he was still experiencing discomfort and because of the media reports about thrombi/bleeding as a possible adverse effect of the vaccine he received.

He did not have a headache. Blood tests showed haemoglobin 15.9 g/dL (13.4–17.0), leukocytes 5.5 × 10⁹/L (3.5–10.0), platelets 303 × 10⁹/L (145–390) and D -dimer <0.4 mg/L (<0.5). The Wells score was 0. On the same day, he contacted a radiologist, who performed an ultrasound examination but could not confirm the doctor's suspicion of deep vein thrombosis. Six days later, 29 days after vaccination, he experienced pain in his left lower leg. A new ultrasound examination revealed deep vein thrombosis. He was treated with Apixaban 10 mg × 2 for the first seven days, followed by 5 mg × 2 for three months. The case was reported as an adverse effect on Melde.no.