Britannica Sources used in this answer

Why did declining vaccination rates contribute to increases in whooping cough cases?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Infographic showing estimated lives saved by childhood vaccinations worldwide from 1974 to 2024, with syringe-shaped bars for each disease. Measles tops the list at 93.71 million lives saved, followed by tetanus, whooping cough, and others, for a total of 153.84 million lives saved. — vaccine Vaccines and the estimates of lives saved over the period 1974–2024.

Declining vaccination rates contribute to increases in whooping cough cases primarily by undermining herd immunity.

Herd immunity occurs when a sufficiently large proportion of a population is vaccinated, making it difficult for an infectious disease to spread because the number of susceptible individuals is minimized. When vaccination coverage drops below the necessary threshold, this protective barrier is lost, allowing the disease to circulate more freely among the population.12

This decline in coverage has been driven by a combination of factors, including complacency regarding the severity of vaccine-preventable diseases and concerns—often fueled by misinformation—about the safety of vaccines. Historically, when vaccination rates for pertussis have fallen, it has led to significant outbreaks, resulting in thousands of cases and, in some instances, hundreds of deaths. Maintaining high levels of immunization is therefore essential to protecting public health and preventing the resurgence of this serious respiratory illness.21