Former CDC director: For COVID-19, attempt to build 'herd immunity' is a losing strategyThat turned out not to be the case then, and a herd immunity approach is likely to be inadequate now in the battle against the novel coronavirus. The current discussions of herd immunity often concern hypothetical possibilities and are not based on evidence. No herd immunity figure is meaningful without population density, plus information on the frequency and types of contacts between people. The campaign to eradicate smallpox provided real-life experience demonstrating the inadequacy of herd immunity as a concept or valid target. Vaccines are only part of the solutionThose who advocate a herd immunity approach for controlling the coronavirus have not studied the lessons of the past.