Baker MA, Baer B, Kulldorff M, et al. - Through a study population that involved chiefly commercially insured children from birth to < 24 months of age in 2010 to 2015 from across the US, researchers discovered the existence and extent of any increased risk of Kawasaki disease (an acute vasculitis that principally affects children younger than 5 years of age) in the 28 days after 13-valent pneumococcal conjugate vaccine (PCV13) vaccination. The prespecified risk interval was Days 1–28 following vaccination and a 28-day-long control interval followed this risk interval. A secondary analytic strategy used a cohort design, with alternative likely risk intervals of Days 1–28 and Days 1–42. The differing background risk of Kawasaki disease by age was adjusted for in both designs. There were 43 and 44 validated cases of Kawasaki disease in the risk interval and in the control interval, respectively, in the primary analyses. The age-adjusted risk estimate was 1.07. The risk estimates of potential Kawasaki disease in the risk interval vs in unexposed person-time were 0.84 and 0.97 for the Days 1–28 risk interval and for the Days 1–42 risk interval, respectively, in the secondary, cohort analyses, which involved about 700 potential cases and more than 3 million person-years. Therefore, no data was discovered of a relationship between PCV13 vaccination and Kawasaki disease onset in the 4 weeks following vaccination nor of an increased risk extending or concentrated somewhat beyond 4 weeks, with more than 6 million doses of PCV13 administered. These null outcomes were constant across alternative designs, age-adjustment methods, control intervals, and categories of Kawasaki disease case involved.