The AstraZeneca US Phase III trial of Vaxzevria[^1] has demonstrated favorable reactogenicity and overall safety profile. The vaccine was well tolerated, and the independent data safety monitoring board (DSMB) identified no safety concerns related to the vaccine. The DSMB conducted a specific review of thrombotic events, as well as cerebral venous sinus thrombosis (CVST) with the assistance of an independent neurologist. The DSMB found no increased risk of thrombosis or events characterised by thrombosis among the 21,583 participants receiving at least one dose of the vaccine. The specific search for CVST found no events in this trial.
The Strategic Advisory Group of Experts on Immunization (SAGE), an advisory group to the WHO, recommends the AstraZeneca vaccine for all adults at the age of 18 years and above, including people at the age of 65 years and older. Similarly, the European Medicines Agency (EMA) has established no upper age limit.
Furthermore, the real-life data of the use of the vaccine at great scale coming from the United Kingdom show similar high effectiveness to prevent moderate to severe disease independent of age, and similar to the Pfizer-BioNTech vaccine. Concretely, data from Scotland[^2] showed an effectiveness in preventing hospitalization of 94% (95% CI 73-99) (with similar rates when the data is restricted to the population aged 80 and over (81%; 95% CI 65-90, at 28-34 days after vaccination)) and data from the United Kingdom as a whole[^3] showed an effectiveness of 80.4% (95% CI: 36.4-94.5) for AZ vaccine, with the median age being 88 years; while the effectiveness of the Pfizer vaccine was 71.4% (95% CI: 46.5-90.6), median age 87 years.
- Clinicaltrials.gov. A Phase III Randomized, Double-blind, Placebo-controlled Multicenter Study in Adults to Determine the Safety, Efficacy, and Immunogenicity of AZD1222, a Non-replicating ChAdOx1 Vector Vaccine, for the Prevention of COVID-19. [Online] Available at: https://clinicaltrials.gov/ct2/show/NCT04516746?term=NCT04516746&draw=2&rank=1. Last accessed: March 2021.
- Vasileiou E, Simpson CR, Robertson C, Shi T, Kerr S, et al. Effectiveness of First Dose of COVID-19 Vaccines Against Hospital Admissions in Scotland: National Prospective Cohort Study of 5.4 Million People. Available at SSRN: https://ssrn.com/abstract=3789264
- Hyams C, Marlow R, Maseko Z, King J, Ward L, Fox K, et al. Assessing the Effectiveness of BNT162b2 and ChAdOx1nCoV-19 COVID-19 Vaccination in Prevention of Hospitalisations in Elderly and Frail Adults: A Single Centre Test Negative Case-Control Study. Available at SSRN: https://ssrn.com/abstract=3796835 or http://dx.doi.org/10.2139/ssrn.3796835