A new collaborative study has found that while a Covid vaccine mandate was successful in speeding up vaccine take-up by Year 12 students who wanted to attend 2021 Leavers celebrations in Dunsborough, it didn’t lead to any new vaccinations.

Led by researchers from The University of Western Australia and University of Newcastle, the study found the increase in uptake was largely a ‘pull-forward’ effect, with many students likely to have been vaccinated eventually regardless.

The study, which included more than 46,000 Year 11 and Year 12 WA students, aimed to measure the effect of WA’s 2021 ‘Leavers mandate’, which required Year 12 students to have at least one Covid vaccine dose to attend Leavers celebrations in Dunsborough, an annual event run by WA Police.

The research team compared the vaccination behaviour of Year 12s (eligible for Leavers) and Year 11s (not eligible to attend).  

Co-author Professor Katie Attwell, who leads VaxPolLab in UWA’s School of Social Sciences, said the Leavers mandate was relatively gentle when compared to other mandates barring unvaccinated people from attending childcare, school or their place of work.

“Missing leavers because you did not want to be vaccinated would be a big deal for many Year 12s,” Professor Attwell said.

“But that consequence is not as serious as some of the other vaccine mandates we have for childhood vaccines or that we had for Covid vaccines.”

Lead author Dr Fabio Martinenghi, from the University of Newcastle, said the study looked at whether a vaccine mandate convinced people to vaccinate or simply made them get vaccinated sooner than they otherwise would have.

“The most important finding of the research is that the mandate changed the speed of vaccine take-up rather than changing young people’s minds about whether to get vaccinated,” he said.

“We used mathematical modelling to work out under what conditions vaccine mandates using deadlines could induce new vaccinations. By the deadline, vaccination among Year 12 students was 15.5 per cent higher than it would have been without the policy.”

The study does not reveal how many students chose the consequence of missing Leavers instead of getting vaccinated. However, WA’s extremely high vaccine coverage rates indicate that the number was likely to be very small.

Professor Attwell said the findings were important because vaccination speed could save lives.

“For a fast-spreading or seasonal virus, being vaccinated before a wave arrives is what protects people and hospitals,” she said.

“It shows mandates don’t need to be heavy-handed and it’s a lesson about how mandates are judged.”

Dr Martinenghi said most evaluations only measured the jump in vaccinations at the deadline, which mixes up people who got the vaccine earlier than otherwise, and those who only got vaccinated because of the mandate.

“Policies need to be assessed over the long run to separate the two,” he said.

The study used existing, de-identified government administrative data, which linked records of every first-dose Covid vaccination (from the Australian Immunisation Register) with dates of birth and school information from June 2021 to May 2022.

Dr Martinenghi said the mathematical model showed such policies — combining deadline-based incentives with lower forms of coercion — could lead to even stronger impacts in populations with greater levels of vaccine hesitancy.

They could be considered for the design of future vaccination policies, such as flu vaccination or measles campaigns, he said.

The research was conducted as part of the MandEval project evaluating COVID-19 vaccine mandates in Australia, the US and Europe. The four-year project is funded by the Medical Research Future Fund of Australia and led by Professor Attwell.