The Qidong Hepatitis B Intervention Study , a population-based , cluster randomized , controlled trial between 1985 and 1990 in Qidong , China , included 39,292 newborns who were randomly assigned to the vaccination group in which 38,366 participants completed the HBV vaccination series and 34,441 newborns who were randomly assigned to the control group in which the participants received neither a vaccine nor a placebo .