Adverse events after Covid vaccination are very rare, according to the most recent study on the topic.
Findings from the Mexican study are published in the journal Neurology.
Researchers used data from the Mexican Ministry of Health to analyse stroke incidence per million Covid-19 vaccination doses in hospitalised adults from December 2020 to August 2021.
Strokes were only reported if they occurred within the first 30 days after vaccination.
During the study, 79,399,446 doses of six different COVID-19 vaccines from Pfizer/BioNTech, AstraZeneca, Sinovac Biotech, CanSino Biologics, Johnson & Johnson and Sputnik V were administered.
A total of 28,646 adverse events occurred within the 30-day time frame.
Of those, 27,968 (98 per cent) were classified as non-serious, and 56 were confirmed as stroke.
Overall, there were 0.71 stroke cases per 1000,000 doses and the median time from vaccination to stroke was two days.
The most frequent stroke was ischemic stroke, occurring in 42 of the 56 patients and nine were haemorrhagic strokes.
The most common risk factors were hypertension (58.9 per cent) and diabetes mellitus (39.3 per cent).
The researchers wrote:
“Our observations suggest that stroke remains an exceedingly rare event among recipients of six different vaccines against SARS-CoV-2.
“Further research is still needed to analyse the potential causal associations between stroke and the different vaccines against SARS-COV-2 vaccines currently available worldwide.”
A large UK study published last month found a very low risk of blood clots after COVID-19 vaccination.
The research showed that people vaccinated with Oxford-AstraZeneca or Pfizer-BioNTech had a lower risk of all arterial clots which can cause strokes and heart attacks, as well as and all venous clots.
A total of one to three extra people per million had an intracranial venous thrombosis after the Oxford-AstraZeneca vaccine.
However, there was no evidence that this was due to the vaccine.
