The most comprehensive study into vaccine side effects so far has uncovered that the Pfizer and Astrazeneca vaccines are linked to serious and potentially life threatening side effects. Although rare, the Pfizer vaccine has been connected to the neurological condition Guillain-Barré syndrome, which carries symptoms of numbness and muscle weakness, while the Astrazenenca vaccine has been associated with bleeding on the brain and haemorrhagic stroke. The Times has the story.
Professor Aziz Sheikh, from the University of Edinburgh, said that it was possible to identify the adverse events only because they were able to look at so much data. The study, published in the journal Nature Medicine, looked at 20 million first doses of the Oxford-AstraZeneca vaccine, 12 million of Pfizer and two million infections.
“These are very rare adverse events. They’re so rare that we’re having to report them per million of the population,” Sheikh said. “It’s not what you’d normally see, where it’s per 1,000 people exposed.”
The work is the largest investigation into potential side effects so far, using data from the UK vaccine programme. It involved comparing occurrences of the conditions in the same people prior to vaccination with occurrences after. In this way it attempted to correct for the possibility that those getting the vaccines were different in other ways from those who did not.
To check the findings, the scientists looked first at English data then checked it with that from Scotland. In doing so, they could not find strong enough evidence to be certain the strokes really were associated with the Pfizer vaccine, but they again found the link between the AstraZeneca jab and Guillan-Barré syndrome. Eighty per cent of people recover completely from Guillain-Barré syndrome, but some can experience long-term ill health.