Study looked at medical problems among 99 million immunised people. Small increases in neurological, blood, heart-related issues were found.
Vaccines that protect against severe illness, death and lingering long Covid-19 symptoms from a coronavirus infection were linked to small increases in neurological, blood, and heart-related conditions in the largest global vaccine safety study to date.
The rare events – identified early in the pandemic – included a higher risk of heart-related inflammation from mRNA shots made by Pfizer Inc, BioNTech SE, and Moderna Inc, and an increased risk of a type of blood clot in the brain after immunisation with viral-vector vaccines such as the one developed by the University of Oxford and made by AstraZeneca Plc.
The viral-vector jabs were also tied to an increased risk of Guillain-Barre syndrome, a neurological disorder in which the immune system mistakenly attacks the peripheral nervous system.
More than 13.5 billion doses of Covid vaccines have been administered globally over the past three years, saving over 1 million lives in Europe alone. Still, a small proportion of people immunised were injured by the shots, stoking debate about their benefits versus harms.
The new research, by the Global Vaccine Data Network, was published in the journal Vaccine last week.
The research looked for 13 medical conditions that the group considered “adverse events of special interest” among 99 million vaccinated individuals in eight countries, aiming to identify higher-than-expected cases after a Covid shot.
Myocarditis, or inflammation of the heart muscle, was consistently identified following a first, second and third dose of mRNA vaccines, the study found.