Latin America (LatAm) has implemented national pediatric vaccination programs to lessen the burden of illnesses caused by viruses such as rotavirus, Haemophilus influenzae type b (Hib), and pneumococcus. The health advantages of vaccination may extend to unvaccinated communities through lowering disease spread. Understanding the herd effect is critical for the implementation and evaluation of vaccination programs. In this study, researchers wanted to undertake a comprehensive evaluation of published epidemiological evidence of herd immunity with Hib, rotavirus, and pneumococcal conjugate vaccines (PCV) in LatAm. Articles published in English, Spanish, or Portuguese (1990-2016) were included in the searches. Following screening and full-text assessment, papers fulfilling the selection criteria were included in the critical appraisal process for observational and interventional research. A herd effect was characterized as a substantial reduction in the incidence of illness, hospitalization, or fatality.
There were 3,465 distinct items found, and 23 of them were included (Hib vaccine n = 5, PCV n = 8, rotavirus vaccine n = 10). The majority of the research included children and/or teenagers. Adult studies, especially those on the elderly over 65 years of age, were few. Few studies found statistically significant decreases in illness incidence in age groups that were not vaccinated. Hospitalization for Hib-confirmed meningitis in children was reduced, but the herd impact could not be assessed. In unvaccinated children, there was some indication of herd effect for PCV and rotavirus vaccines. In adults, there was little evidence of herd effects caused by PCV.
Morbidity/mortality decreases in children not targeted for immunization have been documented in LatAm following the introduction of the Hib, PCV, and rotavirus vaccines. However, there is presently inadequate data to assess the herd effect in adult populations due to methodological constraints. More study and better surveillance are required to characterize the herd impact of these vaccinations in Latin America.
Reference:www.tandfonline.com/doi/full/10.1080/21645515.2018.1514225
