1. Effectiveness of the Pfizer-BioNTech and Oxford-AstraZeneca vaccines on covid-19 related symptoms, hospital admissions, and mortality in older adults in England: test negative case-control study;Bernal;BMJ,2021
2. Bernal JL, Andrews N, Gower C, Gallagher E, Simmons R, Thelwall S, et al. Effectiveness of COVID-19 vaccines against the B.1.617.2 variant. Preprint 16 May 2021. https://khub.net/documents/135939561/430986542/Effectiveness+of+COVID-19+vaccines+against+the+B.1.617.2+variant.pdf/204c11a4-e02e-11f2-db19-b3664107ac42. [Accessed 28 May 2021].
3. Centers for Disease Control and Prevention, CDC. COVID-19 vaccines for children and teens. Updated 26th May 2021. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/adolescents.html. [Accessed 28 May 2021].
4. European Medicines Agency, EMA. First COVID-19 vaccine approved for children aged 12 to 15 in EU. EMA 28 May 2021. https://www.ema.europa.eu/en/news/first-covid-19-vaccine-approved-children-aged-12-15-eu. [Accessed 29 May 2021].
5. International Olympic Committee, International Paralympic Committee. The playbook: athletes and officials. April 2021. https://olympics.com/ioc/tokyo-2020-playbooks. [Accessed 28 May 2021].