Characterising the background incidence rates of adverse events of special interest for covid-19 vaccines in eight countries: multinational network cohort study

This study found large variations in observed rates of adverse events of special interest associated with COVID-19 vaccines by age group and sex, showing need for stratification or standardisation before using background rates for safety surveillance.

SPS commentary:

This quantitative study of background incidence rates of 15 prespecified adverse events of special interest (AESIs). It found that, for example deep vein thrombosis ranged from 387 (95% CI 370 to 404) per 100 000 person years in UK to 1443 (1416 to 1470) per 100 000 person years in US among women aged 65 to 74 years.

 

Some AESIs increased with age. For example, myocardial infarction rates in men increased from 28 (27 to 29) per 100 000 person years among those aged 18-34 years to 1400 (1374 to 1427) per 100 000 person years in those older than 85 years.

 

Other AESIs were more common in young people. For example, rates of anaphylaxis among boys and men were 78 (75 to 80) per 100 000 person years in those aged 6-17 years and 8 (6 to 10) per 100 000 person years in those older than 85 years.

 

The researchers suggest that the same database be used to estimate post-covid-19 vaccine and background rates for comparison in vaccine safety monitoring.

British Medical Journal