Strengths and limitations
This study benefited from a well-established programme, describing the results of a large-scale intervention at national level. The large sample size increases the confidence in the results and allowed for the stratification of distinct covariate effects in promoting early GP visits.The main limitation was the lack of a randomised controlled environment to isolate the effects of the intervention alone in promoting GP visits for individuals classified as vulnerable. However, the study results are aligned with a previous randomised controlled trial conducted by the authors, which demonstrated the increased efficacy of a digital intervention in promoting health service utilisation.The urgency of the situation and the existing system capacity were the paramount issues driving the study design. The comparison with the postal group may have been biased by the purposeful sampling, despite attempts to adjust for the number of usual GP visits in a year. It is possible that the variables affecting access to digital delivery (for example, size of the health provider centre) affected the time to appointment. Several policies were enacted at different times of the COVID-19 pandemic, which may have influenced the results. These include policy changes made by the Australian Department of Health (now the Department of Health and Aged Care), which promoted the use of telehealth by all Australians (including veterans). Telehealth ensured continued access to providers, despite social restrictions, and was sustained throughout the study period. It is possible, however, that the digital group was better set up for telehealth provision.The COVID-19 pandemic may also have changed patient predisposition to attend their GP appointment, or access telehealth appointments. It is also possible that COVID- 19 changes affected the digital behaviour of physicians, enhancing the effect of the digitally delivered intervention. Furthermore, this intervention took place in the Australian health context, which may have influenced early adoption of digital solutions. Different health systems will need to adapt to local technologies and capabilities.