Herd Immunity Can Be Achieved Without Vaccination

Mathematically, herd immunity thresholds (typically 85-95% for highly contagious diseases) can theoretically be reached through natural infection. But the human cost is catastrophic. For measles (herd immunity threshold ~95%), natural-only immunity would require infecting essentially every child in a population. With a case fatality rate of 1-2 per 1,000, a population of 10 million would see 100,000-200,000 child deaths to achieve herd immunity naturally. During 1989-1991, a measles outbreak in unvaccinated communities killed dozens and hospitalized thousands before vaccination restored control. In 2019, New York measles outbreaks infected 600+ people and killed a teenager; all cases were in unvaccinated communities. For polio, achieving natural herd immunity in a naive population would paralyse approximately 1 in 200 infected children; in a population of 1 million, that's 5,000 paralysed children to reach herd immunity. The practical answer is unambiguous: herd immunity 'naturally' means accepting immense preventable suffering. Every major disease eradication or elimination program has relied on vaccination, not natural infection. The only disease eradicated through vaccination is smallpox; no disease has been eradicated through natural infection.