VoICE Immunization Evidence: Herd effects
In a study in Rwanda, the number of admissions to hospital for diarrhea and rotavirus fell substantially after rotavirus vaccine implementation, including among older children age-ineligible for vaccination, suggesting indirect protection through reduced transmission of rotavirus. Two years after rotavirus vaccine introduction, the country saw nearly 400 fewer hospital admissions for diarrhea among young children at 24 district hospitals.
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.
A meta-analysis conducted of data from studies measuring the impact of rotavirus vaccine (RVV) on severe gastroenteritis morbidity and mortality, reported a median herd immunity effect for severe rotavirus gastroenteritis in children less than one year of age of 22% (US and El Salvador). In studies in Latin America reporting an all-cause gastroenteritis benefit the median herd effect for severe gastroenteritis was 24.9%.
Pollard, S.L., Malpica-Llanos, T., Friberg, I.K., . . Walker, N 2015. Estimating the herd immunity effect of rotavirus vaccine. Vaccine. 33(32).
Rotavirus hospital admissions in unvaccinated children aged 2-5 yrs. of age, who where not age-eligible to receive the Rotavirus vaccine (RVV), were reduced by 41%-92% in the US, 30-70% in Australia, 20-64% in Belgium, 35% in Austria and 41-81% in El Salvador following the introduction of RVV. In addition, there was a reduction in hospitalizations due to gastroenteritis of any cause by 17-51% in the US and 40% in Australia.
Patel, M.M., Glass, R., Desai, R., Tate, J.E. & Parashar, U.D. 2012. Fulfilling the promise of rotavirus vaccines: how far have we come since licensure?. Lancet Infectious Diseases. 12(7).
Children with cancer often rely on herd immunity as protection from vaccine-preventable diseases, so vaccinating family members and health workers is critical. Herd effects may be the only source of protection against diseases in which the vaccines are not recommended for immunosuppressed children, such as the measles vaccine.
Ward, E. M., Flowers, C.R., Gansler, T., et al 2017. The importance of immunization in cancer prevention, treatment, and survivorship. CA: A Cancer Journal for Clinicians. 67(5):398-410.