Indirect (herd) protection, following pneumococcal conjugated vaccines introduction: A systematic review of the literature

Gal Tsaban, Shalom Ben-Shimol

Research output: Contribution to journalReview articlepeer-review

88 Scopus citations


Background Pneumococcal diseases are major causes of morbidity among adults, especially those over 50 years of age. While pneumococcal conjugated vaccines (PCV's) impact on pneumococcal disease rates among children is well established, the extent of its impact on adult pneumococcal related illness remains unclear. The aim of this systematic literature review was to describe the impact of PCV introduction to childhood national immunization programs worldwide on PCV-naive adult population. Methods A systematic literature search was performed using the PubMed database. The search was limited to articles written in English and published between January 2000 and February 2016. Studies evaluating pneumococcal disease rates in individuals over 5 years of age were included. Independent extraction of articles was performed by the two authors. Search terms included: Pneumococcal conjugated vaccine, herd, indirect, adults, and pneumonia. Results Forty-nine articles meeting the selection criteria were identified, 39 regarding invasive pneumococcal disease (IPD, one on meningitis only), 8 regarding pneumonia, and 2 on both IPD and pneumonia. The majority of reports were from the US, UK and Canada. Considerable variability in the data sources, quality and completeness was observed. While most studies reported either statistically significant reduction or insignificant changes in IPD and pneumonia disease rates in adults following PCV nationwide implementation, few studies reported statistically significant increase in pneumococcal disease rates, these were mainly from countries with low PCV coverage rates and/or inadequate surveillance. Conclusion Invasive pneumococcal diseases and pneumonia rates among the adult population decreased in most countries following PCV introduction into the NIP. This indirect effect on older population seems to be dependent on PCV coverage rates and time from PCV nationwide implementation. Adults >65 years old seem to benefit the most from PCV introduction.

Original languageEnglish
Pages (from-to)2882-2891
Number of pages10
Issue number22
StatePublished - 19 May 2017


  • Herd protection
  • Indirect immunity
  • Invasive pneumococcal disease (IPD)
  • Pneumococcal conjugated vaccine (PCV)
  • Pneumonia

ASJC Scopus subject areas

  • Molecular Medicine
  • General Immunology and Microbiology
  • General Veterinary
  • Public Health, Environmental and Occupational Health
  • Infectious Diseases


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