Re: Risk of thrombocytopenia and thromboembolism after covid-19 vaccination and SARS-CoV-2 positive testing: self-controlled case series study
Dear Editor
In response to Ruth Sharratt's question, the study was "self-controlled". As I understand it, the 'unvaccinated " controls are represented by those time periods in the dataset BEFORE the vaccination date. A clear spike in thrombocytopenic thromboembolism occurs, in the immediate post-vaccination period.
"The self-controlled case series was originally developed to assess risks of adverse events to vaccination (16 ). The case series determines the relative incidence of the outcome of interest for exposed time periods (eg, after vaccination or SARS-CoV-2 infection) compared with unexposed baseline periods in people with the outcome of interest (see supplementary fig 1). Inference is within people and therefore this implicitly controls for all covariates that remain constant during the study period. "
The Authors explain why they chose this methodology, in the "Strength and Limitations" discussion.
The national rates of thrombocytopenia and thromboembolism are published elsewhere (1), who also provide the clear "all-cause mortality" comparisons between vaccinated and unvaccinated, by age group, sought by Imran Usmani.
Rapid Response:
Re: Risk of thrombocytopenia and thromboembolism after covid-19 vaccination and SARS-CoV-2 positive testing: self-controlled case series study
Dear Editor
In response to Ruth Sharratt's question, the study was "self-controlled". As I understand it, the 'unvaccinated " controls are represented by those time periods in the dataset BEFORE the vaccination date. A clear spike in thrombocytopenic thromboembolism occurs, in the immediate post-vaccination period.
"The self-controlled case series was originally developed to assess risks of adverse events to vaccination (16 ). The case series determines the relative incidence of the outcome of interest for exposed time periods (eg, after vaccination or SARS-CoV-2 infection) compared with unexposed baseline periods in people with the outcome of interest (see supplementary fig 1). Inference is within people and therefore this implicitly controls for all covariates that remain constant during the study period. "
The Authors explain why they chose this methodology, in the "Strength and Limitations" discussion.
The national rates of thrombocytopenia and thromboembolism are published elsewhere (1), who also provide the clear "all-cause mortality" comparisons between vaccinated and unvaccinated, by age group, sought by Imran Usmani.
References
1. ONS https://assets.publishing.service.gov.uk/government/uploads/system/uploa...
Competing interests: No competing interests