Is the immunity acquired during the first COVID-19 wave enough for “herd immunity”?
The term “herd immunity” refers to the generation of population immunity that protects a region, or country, from infection. The number of confirmed COVID-19 cases has reached approximately 5.6 million.2 The world population is estimated to be 7.8 billion. To ascertain the extent of herd immunity, it is pivotal to define the prevalence of SARS-CoV-2-exposed humans. It is thought that 60% is the minimum percentage of symptomatic or asymptomatic COVID-19 population required for herd immunity. That is to say that worldwide herd immunity may occur when ⁓5 billion humans have a protective immune response against SARS-CoV-2. To date, there are no reliable data, particularly on the number of asymptomatic individuals that show seroconversion, to determine the degree of herd immunity.43