Citation Select	Chemaitelly H, Bertollini R, Abu-Raddad LJ; National Study Group for COVID-19 Epidemiology Efficacy of Natural Immunity against SARS-CoV-2 Reinfection with the Beta Variant N Engl J Med. 2021 Dec 30;385(27):2585-2586. doi: 10.1056/NEJMc2110300
Citation Select	Hansen CH, Michlmayr D, Gubbels SM, Mølbak K, Ethelberg S Assessment of protection against reinfection with SARS-CoV-2 among 4 million PCR-tested individuals in Denmark in 2020: a population-level observational study Lancet. 2021 Mar 27;397(10280):1204-1212. doi: 10.1016/S0140-6736(21)00575-4