Related Experiment Video
Updated: May 23, 2026
A Clinical Trial Assessing the Safety, Efficacy, and Delivery of Olive-Oil-Based Three-Chamber Bags for Parenteral Nutrition
Published on: September 20, 2019
A randomised controlled trial to compare opt-in and opt-out parental consent for childhood vaccine safety
Jesia G Berry1, Philip Ryan, Michael S Gold
1Discipline of Public Health, University of Adelaide, Level 6, Bice Building, Royal Adelaide Hospital, Mail Drop DX650 511, Adelaide, South Australia, Australia. jesia.berry@adelaide.edu.au
Insights
Opt-out consent significantly increases participation and sample representativeness in health research compared to opt-in. This supports waiving informed consent when criteria are met for data linkage studies.
Area of Science:
- Health Services Research
- Clinical Trials
- Data Linkage
Background:
- Ethics committees and data custodians often require informed consent even when waivers are appropriate for health research.
- Privacy regulations permit waivers of consent for data linkage studies meeting specific criteria.
Purpose of the Study:
- To compare the effectiveness of opt-in versus opt-out consent strategies for recruiting participants into a data linkage study for vaccine safety surveillance.
- To assess the impact of consent strategies on sample representativeness and feasibility of data linkage.
Main Methods:
- A single-blind, parallel-group randomized controlled trial involving 1129 families of newborns in South Australia.
- Participants were randomized to either an opt-in or opt-out consent procedure for linking childhood immunization and hospital records.
- A subsequent telephone interview assessed parental intentions and sociodemographic differences between participants and non-participants.
Main Results:
- The opt-out arm achieved a 96% participation rate, while the opt-in arm had only 21% participation.
- The opt-in sample was biased towards older, more educated, and higher socioeconomic status individuals.
- The opt-out sample was largely representative of the general population, with minor differences observed in gender.
Conclusions:
- The opt-out consent strategy is highly effective in achieving high participation rates and representative samples for data linkage studies.
- Ethics committees and data custodians should grant waivers of consent for eligible data linkage research to facilitate public health surveillance.
- The findings support the appropriate use of waived consent in health and medical research when privacy criteria are met.
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 (χ(2) (1 df) = 567.7, p<0.001). Participants in the opt-in arm were more likely than non-participants to be older, married/de facto, university educated and of higher socioeconomic status. Participants in the opt-out arm were similar to non-participants, except men were more likely to opt out. Substantial proportions did not receive, understand or properly consider study invitations, and opting in or opting out behaviour was often at odds with parents' stated underlying intentions.
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.
Trial Registration Number:
Australian New Zealand Clinical Trials Registry ACTRN12610000332022.
More Related Videos
06:28E-Patient Counseling Trial (E-PACO): Computer Based Education versus Nurse Counseling for Patients to Prepare for Colonoscopy
Published on: August 1, 2019
05:32Comparing Eye-tracking Data of Children with High-functioning ASD, Comorbid ADHD, and of a Control Watching Social Videos
Published on: December 7, 2018
Related Concept Videos
01:19Pharmacovigilance
This process, termed pharmacovigilance, aims to detect, evaluate, and minimize harmful effects related to medication use. The data collection for pharmacovigilance depends on spontaneous reporting systems, where healthcare professionals or patients voluntarily report suspected ADRs.
In some cases, there...
01:23Types of Biopharmaceutical Studies: Controlled and Non-Controlled Approaches
Non-controlled studies, commonly employed for initial exploration, lack a control group, rendering them susceptible to biases and external influences. In contrast, controlled...
01:20Study Designs in Epidemiology
Observational studies are those where the researcher does not intervene but rather observes natural variations. They include cross-sectional, cohort, and case-control studies.
01:51Vaccinations
01:20Bioequivalence Experimental Study Designs: Completely Randomized and Randomized Block Designs
01:13Bioequivalence studies: Biowaivers