1. WHO Coronavirus (COVID-19) Dashboard [Internet]; 2022. Available from: https://covid19.who.int/.
2. SARS-COV-2 variants: differences and potential of immune evasion;Hirabara;Front Cell Infect Microbiol,2022
3. Persistence and evolution of SARS-CoV-2 in an immunocompromised host;Choi;New Engl J Med,2020
4. Saudi Arabia offers booster shots to adults three months after their second dose [Internet]; 2021. Available from: https://saudigazette.com.sa/article/614951.
5. COVID 19 Dashboard: Saudi Arabia [Internet]; 2022. Available from: https://covid19.moh.gov.sa/.