In a first, rare blood clot case linked to Moderna mRNA vaccine reported in US

So far, it was thought that only adenoviral vector-based vaccines — such as the AstraZeneca vaccine — caused rare blood clots.

A medical worker fills a syringe with a dose of the Moderna Inc. Covid-19 vaccine | Representational image | David Mareuil | Anadolu Agency via Bloomberg

New Delhi: In a first, scientists have reported a case of a man in the US developing blood clots, combined with low platelet counts, after being vaccinated with both doses of the mRNA-based Moderna vaccine.

So far, it was thought that only adenoviral vector-based vaccines — such as the AstraZeneca vaccine — caused the condition, known as thrombocytopenia with thrombosis syndrome (TTS), or vaccine-induced TTS (VITT).

The report, published in the Annals of Internal Medicine Monday, described the case of a 65-year-old man with chronic hypertension and hyperlipidemia (a condition in which there is high level of fat particles in the blood).

The patient went to the Western Pennsylvania Hospital in the American city of Pittsburgh after one week of leg pain, intermittent headaches, and two days of breathing difficulties. It was 10 days after he had received a second dose of the Moderna vaccine (mRNA-1273).

The patient had no known exposure to heparin, a medication that has been associated with TTS. The team was unable to identify any other causes of TTS in the patient.

Despite rapid and exhaustive treatment, the patient died.

The vaccine situation

The Oxford-AstraZeneca vaccine — available in India under the name of Covishield — has been linked to a slightly increased risk of a drop in platelet count and blood clots in arteries.

No such risk has been linked to the Pfizer-BioNTech mRNA vaccine, also known as the BNT162b2 vaccine.

The latest findings may be of relevance to India, which may soon have access to the Moderna vaccine by next year, via collaboration with the Mumbai-based pharmaceutical giant Cipla.

The team noted that Covid vaccines using mRNA technology are proven safe and effective, and have been used with no such events in millions of people.

This study is the only report to date of possible VITT or TTS in an mRNA vaccine recipient.

The scientists concluded that such rare events should not discourage others from receiving the benefits of these vaccines since there is already a high risk of blood clots among Covid patients.