Vaccination has been used for the prevention and eradication of communicable diseases such as smallpox, polio, and measles. Herd immunity and immunity threshold have already been conceptualized for the prevention of outbreaks and pandemicity of these diseases. Coronavirus infectious disease-19 (COVID-19) is the second pandemic coronavirus disease of the 21st century. Vaccination has been conducted since December 2020 in an attempt to control the pandemic. The morbidity and incidence of COVID-19 has decreased since the initiation of the vaccination program within Israel, the United Kingdom, and the United States. However, irregular vaccine rollout and uneven distribution of vaccine is a major barrier to vaccine access. Moreover, genetic variants of the severe acute respiratory syndrome coronavirus 2 (SARS CoV-2) could be a barrier to immunity.
Addressing the 21st Century Challenges to Herd Immunity