Adapting group sequential methods to observational postlicensure vaccine safety surveillance: results of a pentavalent combination DTaP-IPV-Hib vaccine safety study.
Nelson JC, Yu O, Dominguez-Islas CP, Cook AJ, Peterson D, Greene SK, Yih WK, Daley MF, Jacobsen SJ, Klein NP, Weintraub ES, Broder KR, Jackson LA. Adapting group sequential methods to observational postlicensure vaccine safety surveillance: results of a pentavalent combination DTaP-IPV-Hib vaccine safety study. Am J Epidemiol. 2013 Jan 15; 177(2):131-41.