Fig 1. The incidence of intussusception at three different periods.

a) The crude and b) the smoothed incidence of intussusception per 100 000 person years during pre-vaccination years (1999–2005) with blue line, when vaccine was sold (2006–2009) with red line, and after the immunisation programme implementation (2010–2013) with green line by month of age for children less than 1 year in Finland. Fig is based on National Hospital Discharge Register data, and case verification has not been performed. Cases were referred to as 1 month of age from 15 days to 45 days of age, 2 months from 46 to 75 days of age etc.