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New research examines how COVID-19 infections and hospitalisations could be reduced through national vaccine campaigns.
Australia’s protection against coronavirus disease 2019 (COVID-19) is waning.
In April of 2022, 95% of Australians over the age of 16 had received at least two COVID-19 vaccine doses, but uptake of booster doses since then has been low.
As of July 2024, only 7% of Australians aged 18–64 years and 44% of Australians over the age of 65 had received a COVID-19 vaccine in the past 12 months.
In a research article published in the Medical Journal of Australia, researchers from the Burnet Institute and Monash University have analysed how vaccination coverage could be improved through ongoing vaccination strategies, similar to the annual campaigns used for influenza vaccination.
“Influenza vaccination campaigns are scheduled for winter each year to maximise their impact, given the seasonal nature of epidemic waves,” Fenella McAndrew and co-authors wrote.
“In Australia, government advertising, workplace promotions, and free vaccination for people at particular risk of severe influenza means that annual population coverage is typically about 30%.”
“COVID-19 vaccination strategies in the context of low vaccine uptake, non-seasonal epidemic waves and waning immunity from both vaccination and past infection have not been assessed. We therefore modelled the impact of different COVID-19 vaccination strategies, with the aim of providing insights for future vaccination guidelines.”
Projecting into the future
The researchers used dynamic compartmental modelling to assess the effects of various COVID-19 vaccination strategies, including no vaccination campaigns, increased vaccination coverage throughout the year and timed vaccination campaigns with similar rollout coverage to existing flu vaccination campaigns.
“As future epidemic wave patterns are unknown, all vaccination scenarios were run with several sets of different assumptions regarding the periodicity of epidemic waves,” the authors wrote.
The modelling was built on the baseline vaccination rate that was present in Victoria in July 2024, with the assumption that any new COVID-19 variants would be Omicron subvariants, and that most of the population would have hybrid immunity acquired from vaccine and virus exposure.
Scenarios were run for 15 years, with a steady epidemic wave pattern being reached during the first five years, and outcomes projected from the following ten-year period.
“The model was highly sensitive to the start and end of the measurement period because of variations in epidemic wave periodicity and magnitude. The results converged and were less sensitive to the choice of start or end points if the model was run for ten years rather than one or five years; each scenario was therefore projected over a ten-year period,” the authors wrote.
The results
In scenarios featuring annual vaccination campaigns, there was a 1–13% reduction in mean infections and a 3–14% reduction in mean hospitalisations.
Increasing vaccination coverage, specifically for people over the age of 65, showed a reduction in hospitalisation of 9–26%, but the researchers note that achieving this would require twice as many vaccine doses as a general population strategy.
High uniform coverage with vaccinations spread across the year resulted in the greatest reduction in mean incidence of infections and hospitalisation.
“Our model suggests that starting COVID-19 vaccination campaigns in March, at the same time as influenza vaccination campaigns, could be effective in reducing numbers of SARS-CoV-2 infections and COVID-19-related hospitalisations, with the degree of benefit depending on assumptions about epidemic wave patterns,” the authors wrote.
“If this finding can be extrapolated to all of Australia, it would be equivalent to averting the number of hospitalisations attributed to an entire influenza season.”
Read the research in the Medical Journal of Australia.
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