VoICE Immunization Evidence: Herd effects

Key Concept

Key Evidence: Data obtained through active surveillance pre and post introduction of PCV in the US showed that the vaccine averted an estimated 38,000 cases of invasive pneumococcal disease within its first five years of use. Additionally, 71,000 cases of disease were estimated to be prevented by herd effects.

Ray, G.T., Whitney, C., Fireman, B., et al 2006. Cost-effectiveness of pneumococcal conjugate vaccine: evidence from the first 5 years of use in the United States incorporating herd effects. Pediatric Infectious Disease Journal. 25:494-501.

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Key Evidence: Following the introduction of PCV-10 for infants in Brazil, which included catch-up vaccination for children 7-23 months old and achieved high coverage (82% increasing to 94% within 5 years), hospitalization rates for pneumonia from any cause declined over the next five years by 11-27% in persons 5-49 years of age, after adjusting for trends with other causes of hospitalization.

From the VoICE Editors: Note that the rate for the elderly (65+) increased by 15% over this period —  a trend that preceded the introduction of the vaccine. 

Andrade AL, Afonso ET, Minamisava R et al. 2017. Direct and indirect impact of 10-valent pneumococcal conjugate vaccine introduction on pneumonia hospitalizations and economic burden in all age groups in Brazil: A time-series analysis. PLoS One. 12(9).

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Key Evidence: Assuming 90% coverage, a program in The Gambia using a 9-valent PCV (PCV9) would prevent approximately 630 hospitalizations, 40 deaths, and 1000 DALYs over the first 5 years of life of a birth cohort. The estimated cost would be $670 per DALY averted in The Gambia.

Kim, S., Lee, G. and Goldie, S. 2010. Economic evaluation of pneumococcal conjugate vaccination in The Gambia. BMC Infectious Diseases. 10:260.

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Key Evidence: In one of the first studies of real-world use of pneumococcal conjugate vaccine (PCV) in Africa, the 10-strain vaccine introduced in Kenya for infants and provided to all children under five in “catch-up” campaigns reduced the incidence of any cause of pneumonia confirmed by a chest X-ray by nearly half (48%) in children 2-59 months of age over a five-year period. This sharp reduction in radiological-confirmed pneumonia is more than twice the reduction seen in several clinical trials of PCV in Africa and Latin America which was around 20-23%.

From the VoICE Editors: The sharp reduction in radiological-confirmed pneumonia as a result of immunization in this study is likely because – unlike in some clinical trials – the herd effects of the vaccine on unvaccinated children were prospectively captured in the study.

Silaba M, Ooko M, Bottomley D et al. 2019. Effect of 10-valent pneumococcal conjugate vaccine on the incidence of radiologically-confirmed pneumonia and clinical-defined pneumonia in Kenyan children: an interrupted time-series analysis. Lancent Global Health. 7.

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Key Evidence: In Rwanda, the number of hospital admissions for diarrhea and rotavirus fell substantially after rotavirus vaccine (RVV) introduction, including among older children age-ineligible for vaccination. This suggests indirect protection through reduced transmission of rotavirus. Two years after RVV introduction, the country had nearly 400 fewer hospital admissions for diarrhea among young children.

Ngabo, F., Tate, J.E., Gatera, M., et al 2016. Effect of pentavalent rotavirus vaccine introduction on hospital admissions for diarrhea and rotavirus in children in Rwanda: a time-series analysis. Lancet Global Health. 4:e129-36.

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Key Evidence: After PCV13 replaced PCV7 in the U.S. infant immunization program in 2010, the incidence of invasive pneumococcal disease (IPD) caused by the 6 additional serotypes in the new vaccine declined by 75% in children too old to be vaccinated (5-17 years) by the third year following the switch, and by 58-72% in adults, compared to the expected incidence if PCV7 alone had been continued. This led to overall reductions in IPD incidence of 53% in 5-17 year olds and of 12-32% in adults within three years of the switch from PCV7 to PCV13.

Moore MR, Link-Gelles R, Schaffner W et al. 2015. Effect of use of 13-valent PCV in children on invasive pneumococcal disease in children and adults in the USA: analysis of multisite, population-based surveillance. Lancet. 15.

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Key Evidence: According to a study using local epidemiological data in China, vaccinating infants with pneumococcal conjugate vaccine (PCV-13), using a 3+1 schedule, would prevent more than 10 times as many deaths from invasive pneumococcal disease and pneumonia in unvaccinated individuals (147,500 per year) than it would prevent directly in those vaccinated (12,800 per year). This would be due mainly to a reduction in hospitalizations for pneumonia.

Shen K, Wasserman M, Liu D et al. 2018. Estimating the cost-effectiveness of an infant 13-valent pneumococcal conjugate vaccine national immunization program in China. PLoS One. 13(7).

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Key Evidence: A meta-analysis of studies measuring the impact of rotavirus vaccine (RVV) on severe gastroenteritis morbidity and mortality, found a 22% herd immunity effect for severe rotavirus gastroenteritis in children less than one year of age in US and El Salvador.  In Latin America, severe gastroenteritis due to any cause was reduced by 25%.

Pollard, S.L., Malpica-Llanos, T., Friberg, I.K., . . Walker, N 2015. Estimating the herd immunity effect of rotavirus vaccine. Vaccine. 33(32).

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Key Evidence: A large study in Norway found that the overall incidence of invasive pneumococcal disease (IPD) declined significantly in individuals on immunosuppressive drugs following the introduction of PCVs for infants — and most significantly in people undergoing chemotherapy. These findings underscore the benefits that childhood vaccination with PCVs affords the entire population.

Steens A, Winje BA, White RA et al. 2019. Indirect effects of pneumococcal childhood vaccination in individuals treated with immunosuppressive drugs in ambulatory care: a case-cohort study. Clinical Infectious Diseases. 68(8).

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Key Evidence: According to a modeled data study on cholera transmission in Bangladesh, a cholera vaccination program for 1-14 year olds in the slums of Dhaka, Bangladesh involving periodic (every 3 years) campaigns would reduce cholera incidence in adults living in these areas by 40% due to the herd effects of oral cholera vaccines.

Khan IK, Levin A, Chai DL, DeRoeck D et al. 2018. The impact and cost-effectiveness of controlling cholera through the use of oral cholera vaccines in urban Bangladesh: a disease modeling and economic analysis. PLoS NTD. 12(10).

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