Individuals cannot rely on COVID-19 herd immunity: Durable immunity to viral disease is limited to viruses with obligate viremic spread
Jonathan W. Yewdell
Abstract
It is often messaged that herd immunity to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV2 (CoV-2)), the causative agent of Coronavirus Disease 2019 (COVID-19), will protect nonvaccinated individuals from infection. Herd immunity refers to the concept that when a sufficient fraction of individuals in a population develop immunity from infection or vaccination, viral transmission is reduced to a near negligible level. However, seasonal CoVs, which cause approximately 20% of common colds, remain endemic, even though demonstrating only limited antigenic evolution in epitopes targeted by neutralizing antibodies Although there are only 4 circulating seasonal CoVs, infections frequently recur, even yearly, likely related to waning antibody levels Human challenge studies established that seasonal CoV reinfection with the identical strain can occur within a year after initial exposure, though typically with reduced shedding and milder symptoms Reinfection also appears to occur following mild COVID-19 cases, where the serum neutralizing antibody half-life is only approximately 5 weeks