An observational Swedish study yesterday in BMJ reveals an elevated risk of serious blood clots and abnormal bleeding up to 6 months after recovery from COVID-19.

A team led by Umea University researchers analyzed data from national registries in Sweden to follow 1,057,174 people diagnosed as having COVID-19 and 4,076,342 matched, uninfected controls from Feb 1, 2020, to May 25, 2021. They used a self-controlled case series (up to 6 months after diagnosis) and matched-cohort study design (first 30 days).

Thirty-seven cases were likely reinfections. Average patient age was 40.2 years, and 51% were women.