Whiteley, William N., Ip, Samantha, Cooper, Jennifer A., Bolton, Thomas, Keene, Spencer, Walker, Venexia, Denholm, Rachel, Akbari, Ashley, Omigie, Efosa, Hollings, Sam, Di Angelantonio, Emanuele, Denaxas, Spiros, Wood, Angela, Sterne, Jonathan A. C., and Sudlow, Cathie
Background Thromboses in unusual locations after the Coronavirus Disease 2019 (COVID-19) vaccine ChAdOx1-S have been reported, although their frequency with vaccines of different types is uncertain at a population level. The aim of this study was to estimate the population-level risks of hospitalised thrombocytopenia and major arterial and venous thromboses after COVID-19 vaccination. Methods and findings In this whole-population cohort study, we analysed linked electronic health records from adults living in England, from 8 December 2020 to 18 March 2021. We estimated incidence rates and hazard ratios (HRs) for major arterial, venous, and thrombocytopenic outcomes 1 to 28 and >28 days after first vaccination dose for ChAdOx1-S and BNT162b2 vaccines. Analyses were performed separately for ages Of 46 million adults, 23 million (51%) were women; 39 million (84%) were 28 days post-ChAdOx1-S, 359 (338 to 382), [less than or equal to]28 days post-BNT162b2-S, 241 (229 to 253); >28 days post-BNT162b2-S 277 (263 to 291). The crude incidence rates (per 100,000 person-years) of all arterial events were as follows: prevaccination, 546 (95% CI: 541 to 555); [less than or equal to]28 days post-ChAdOx1-S, 1,211 (1,185 to 1,237); >28 days post-ChAdOx1-S, 1678 (1,630 to 1,726), [less than or equal to]28 days post-BNT162b2-S, 1,242 (1,214 to 1,269); >28 days post-BNT162b2-S, 1,539 (1,507 to 1,572). Adjusted HRs (aHRs) 1 to 28 days after ChAdOx1-S, compared with unvaccinated rates, at ages Rates of intracranial venous thrombosis (ICVT) and of thrombocytopenia in adults aged The main limitations of the study are as follows: (i) it relies on the accuracy of coded healthcare data to identify exposures, covariates, and outcomes; (ii) the use of primary reason for hospital admission to measure outcome, which improves the positive predictive value but may lead to an underestimation of incidence; and (iii) potential unmeasured confounding. Conclusions In this study, we observed increases in rates of ICVT and thrombocytopenia after ChAdOx1-S vaccination in adults aged, Author(s): William N. Whiteley 1,2,*, Samantha Ip 3, Jennifer A. Cooper 4, Thomas Bolton 3,5, Spencer Keene 3, Venexia Walker 4, Rachel Denholm 4, Ashley Akbari 6, Efosa Omigie 7, [...]