Estimated Population-Level Impact of Pneumococcal Conjugate Vaccines Against All-Cause Pneumonia Mortality Among Unvaccinated in 5 Latin American Countries

Abstract

Background: Pneumococcal conjugate vaccines (PCVs) provide strong direct protection in children, while limited data are available on their indirect effect on mortality among older age groups. This multicountry study aimed to assess the population-level impact of pediatric PCVs on all-cause pneumonia mortality among children ≥5 years of age, and invasive pneumococcal disease (IPD) cases in Chile.

Methods: Demographic and mortality data from Argentina, Brazil, Chile, Colombia, and Mexico were collected considering the ≥ 5-year-old population, from 2000 to 2019, with 1 795 789 deaths due to all-cause pneumonia. IPD cases in Chile were also evaluated. Time series models were employed to evaluate changes in all-cause pneumonia deaths during the postvaccination period, with other causes of death used as synthetic controls for unrelated temporal trends.

Results: No significant change in death rates due to all-cause pneumonia was detected following PCV introduction among most age groups and countries. The proportion of IPD cases caused by vaccine serotypes decreased from 29% (2012) to 6% (2022) among people aged ≥65 years in Chile.

Discussion: While an effect of PCV against pneumonia deaths (a broad clinical definition that may not be specific enough to measure indirect effects) was not detected, evidence of indirect PCV impact was observed among vaccine-type-specific IPD cases.

Keywords: Latin American countries; all-cause pneumonia; indirect effects; interrupted time series; mortality; national registry; pneumococcal conjugate vaccines; pneumococcus; synthetic control model; vaccine impact.

Figure 1.

Annual time series for the proportion of all deaths recorded as pneumonia (International Classification of Diseases, Tenth Revision [ICD-10] codes J12–J18) as primary cause of death, by age group in 5 Latin American countries. Vertical dashed lines represent the timing of universal pneumococcal conjugate vaccine introduction.

Figure 2.

Estimated impact of pneumococcal conjugate vaccine among age groups 5–19, 20–39, 40–64, 65–79, and 80+ years using the SC, ITS, and SC + ITS modeling approaches, by country. Rate ratios were calculated by dividing the cumulative number of observed pneumonia deaths by the cumulative number of predicted pneumonia deaths during the evaluation period. Black squares represent the point estimates of rate ratio and bars represent their 95% credible intervals. A rate ratio < 1 indicates evidence of indirect protection effect of the vaccine; a rate ratio = 1 indicates no evidence of indirect effect of the vaccine; while a rate ratio > 1 indicates evidence of indirect detrimental effect of the vaccine. Abbreviations: ITS, interrupted time series model; SC, synthetic control model.

Figure 3.

Serotype distribution of Streptococcus pneumoniae strains isolated from invasive pneumococcal disease among older adults ≥65 years of age, in Chile, 2012–2022. On top of each stacked bar plot, the total number of isolates is shown. PCV13x includes serotypes 3, 6A, and 19A. Abbreviation: PCV, pneumococcal conjugate vaccine. Source: Laboratorio de Referencia de Agentes de Meningitis Bacteriana, Departamento de Laboratorio Biomedico, ISP.