Preparing for safety monitoring after rotavirus vaccine introduction - Assessment of baseline epidemiology of intussusception among children <2 years of age in four Asian countries.

Intussusception is the invagination of one segment of the bowel into a distal segment, characterized by symptoms of bloody stool, vomiting, and abdominal pain. Previous studies have found regional differences in incidence but the etiology of most intussusception cases is unknown. Rotavirus vaccines were associated with a slightly of increased risk of intussusception in post-licensure evaluations in high- and middle-income countries, but not in low income African countries. To describe the baseline epidemiology of intussusception in young children prior to rotavirus vaccine implementation, active sentinel hospital surveillance for intussusception in children < 2 years of age was conducted in 4 low income Asian countries (Bangladesh, Nepal, Pakistan and Vietnam). Over a 24-month period, 15 sites enrolled 1,415 intussusception cases, of which 70% were enrolled in Vietnam. Overall, 61% of cases were male and 1% (n = 16) died, ranging from 8% in Pakistan to 0% in Vietnam. The median age of cases enrolled ranged from 6 months in Bangladesh and Pakistan to 12 months in Vietnam. The proportion of cases receiving surgical management was 100% in Bangladesh, 88% in Pakistan, 61% in Nepal, and 1% in Vietnam. The high proportion of males and median age of cases around 6 months of age found in this regional surveillance network are consistent with previous descriptions of the epidemiology of intussusception in these countries and elsewhere. Differences in management and the fatality rate of cases between the countries likely reflect differences in access to healthcare and availability of diagnostic modalities. These baseline data will be useful for post-rotavirus vaccine introduction safety monitoring.