A randomised controlled trial to compare opt-in and opt-out parental consent for childhood vaccine safety surveillance using data linkage
Introduction No consent for health and medical research is appropriate when the criteria for a waiver of consent are met, yet some ethics committees and data custodians still require informed consent.
Methods A single-blind parallel-group randomised controlled trial: 1129 families of children born at a South Australian hospital were sent information explaining data linkage of childhood immunisation and hospital records for vaccine safety surveillance with 4 weeks to opt in or opt out by reply form, telephone or email. A subsequent telephone interview gauged the intent of 1026 parents (91%) in relation to their actions and the sociodemographic differences between participants and non-participants in each arm.
Results The participation rate was 21% (n=120/564) in the opt-in arm and 96% (n=540/565) in the opt-out arm (χ2(1 df) = 567.7, p
Conclusions The opt-in approach resulted in low participation and a biased sample that would render any subsequent data linkage unfeasible, while the opt-out approach achieved high participation and a representative sample. The waiver of consent afforded under current privacy regulations for data linkage studies meeting all appropriate criteria should be granted by ethics committees, and supported by data custodians.