Herd immunity in older adults from a middle‐income country: A time‐series trend analysis of community‐acquired pneumonia mortality 2003–2017

Abstract

Background and Aims Community‐acquired pneumonia is responsible for substantial mortality, and pneumococcus is commonly accepted as a major cause of pneumonia, regardless of laboratory confirmation. Child immunization programs have reported success in decreasing pneumonia mortality: directly in young children and indirectly (herd immunity) in unvaccinated adult populations in some countries. We assess changes in mortality trends for all‐cause pneumonia in older adults associated with the introduction of pneumococcal vaccination for children in Peru. Methods This is a secondary analysis on administrative data collected periodically by the Peruvian Ministry of Health. An observational retrospective time series analysis was conducted using longitudinal population‐based data from death certificates in Peru between 2003 and 2017. The time series includes 6 years before and 9 years after the introduction of the pneumococcal‐conjugated vaccines in the national child immunization program in 2009. Monthly frequencies and annual rates for all‐cause pneumonia deaths in children under 5 years of age and adults over 65 years of age are presented. Linear and quadratic trends are analyzed. Results Deaths among older adults accounted for 75.6% of all‐cause pneumonia mortality in Peru, with 94.4% of these reporting “pneumonia due to unspecified organism” as the underlying cause of death. Comparing pre‐ and post‐child immunization program periods, annual average mortality rates from unspecified pneumonia decreased by 22.7% in young children but increased by 19.6% in older adults. A linear trend model supports this overall tendency, but a quadratic curve explains the data better. Conclusion Pneumococcal‐conjugated vaccines are developed using serotypes prevalent in selected countries from less common (invasive) pneumococcal disease and expected to prevent mortality worldwide from widespread (noninvasive) pneumonia. Our results do not support the presence of herd immunity from pneumococcal vaccination of children for community‐acquired pneumonia in the increasingly ageing population of Peru. This should direct future research and could influence public health policy.

Pneumonia Mortality Trends in Children under 5 Years of Age in the Context of Pneumococcal Conjugate Vaccination in Peru, 2003–2017

“…This suggests that the percentage of deaths among young children due to pneumonia had already decreased before PCVs were available and were later relatively unaltered by PCV introduction. There are previous reports on how, in Peru, (1) PCVs alone cannot explain the trend in infant pneumonia mortality (direct benefit to the vaccinated population) [17] and (2) there is a lack of evidence of herd protection (indirect benefit on the older adult unvaccinated population) following PCV introduction [18]. Also, all-cause infant mortality rates have been dropping globally for decades, but in most countries PCVs have only been available relatively recently [19], so other factors may be involved in infant mortality.…”

“…As additional serotypes are added to new vaccines, questions arise regarding their efficacy in specific settings that were not involved in the design of the vaccine. Considering decreasing global infant mortality trends [19], no evidence of herd immunity [18], an unclear trend in infants [17] and the absence of serotype confirmation in Peru, there is just not enough evidence to support a strong impact from broader PCVs on infant mortality. We can attest to a consistent decrease in pneumonia mortality among young children (infants, toddlers and preschoolers) since 2013 in Peru, but it is unclear whether this trend can be solely explained by PCV intervention.…”

Multi-Classification of Lung Infections Using Improved Stacking Convolution Neural Network

“…Lung disease is a leading cause of death across the globe, and pneumonia, one of the most common infectious diseases, is also one of the leading causes of mortality worldwide [1]. Pneumonia is an infection that occurs in the lungs, and every year it affects approximately 7% of the global population, and four million patients face mortality risks [2].…”