Impact of vaccination and birth rate on the epidemiology of pertussis: a comparative study in 64 countries

• Published in: Proceedings of the Royal Society. B, Biological sciences Vol. 277; no. 1698; pp. 3239 - 3245
• Main Authors: Broutin, H., Viboud, C., Grenfell, B. T., Miller, M. A., Rohani, P.
• Format: Journal Article
• Language: English
• Published: England The Royal Society 07.11.2010
• Subjects: Birth Rate; Birth rates; Bordetella pertussis; Bordetella pertussis - immunology; Comparative Approach; Disease models; Disease Outbreaks - prevention & control; Disease transmission; Epidemics; Epidemiology; Humans; Immunity; Immunity, Herd - immunology; Infections; Models, Immunological; Periodicity; Pertussis; Pertussis Vaccine - administration & dosage; Pertussis Vaccine - immunology; Retrospective Studies; Stochastic Processes; Vaccination; Vaccination - standards; Whooping cough; Whooping Cough - epidemiology; Whooping Cough - immunology; Whooping Cough - transmission; World Health Organization
• ISSN: 0962-8452; 1471-2945; 1471-2954
• DOI: 10.1098/rspb.2010.0994

Bordetella pertussis infection remains an important public health problem worldwide despite decades of routine vaccination. A key indicator of the impact of vaccination programmes is the inter-epidemic period, which is expected to increase with vaccine uptake if there is significant herd immunity. Based on empirical data from 64 countries across the five continents over the past 30–70 years, we document the observed relationship between the average inter-epidemic period, birth rate and vaccine coverage. We then use a mathematical model to explore the range of scenarios for duration of immunity and transmission resulting from repeat infections that are consistent with empirical evidence. Estimates of pertussis periodicity ranged between 2 and 4.6 years, with a strong association with susceptible recruitment rate, defined as birth rate × (1 − vaccine coverage). Periodicity increased by 1.27 years on average after the introduction of national vaccination programmes (95% CI: 1.13, 1.41 years), indicative of increased herd immunity. Mathematical models suggest that the observed patterns of pertussis periodicity are equally consistent with loss of immunity that is not as rapid as currently thought, or with negligible transmission generated by repeat infections. We conclude that both vaccine coverage and birth rate drive pertussis periodicity globally and that vaccination induces strong herd immunity effects. A better understanding of the role of repeat infections in pertussis transmission is critical to refine existing control strategies.