In This Issue

Despite the success of a global eradication effort led by the World Health Organization and partners, polio outbreaks among older children and adults in some countries and reports of declining intestinal immunity after vaccination has led to proposals to include older children in vaccination campaigns, which currently target children 4 years of age and below. To determine the contribution of older children and adults to poliovirus transmission, Isobel Blake et al. (pp. 10604–10609) performed mathematical modeling with polio surveillance data from recent outbreaks among adults and found that in Tajikistan, where a 2010 outbreak led to 518 polio cases, older children and adults minimally transmitted polio, despite developing the disease, compared with children aged 0–5 years. In comparison, during a 2010 outbreak in the Republic of Congo with 442 cases, older children and adults contributed significantly to virus transmission, likely due to socioeconomic conditions that favored disease spread. The authors failed to find evidence for the role of inadequate intestinal immunity in viral spread in either outbreak but estimated that advancing immunization in Tajikistan by 2 weeks might have forestalled 130 cases. According to the authors, countries that have been polio-free might curb outbreaks by responding early rather than expanding the age range of vaccination campaigns. — P.N.