Could a Combined Flu and COVID Vaccine Boost Immunisation Rates?

On a Tuesday in Sydney's south-west, Kenneth McCroary's clinic was full, as it often is. The Campbelltown-based GP sees everyone in his local area — newborns, pregnant women, and patients nearing 100 years old. The hours often stretch long, especially so at this time of year. Flu season in Australia typically hits between April and October, and this year is no exception.

For Dr McCroary, the crunch of these cases has been compounded by a simultaneous uptick in COVID-19 infections. As of Thursday, there had been 102,817 confirmed COVID and more than 138,000 flu cases nationally this year. These viruses are the leading causes of death via acute respiratory infections — 514 and 102 deaths, respectively, between January and April.

Despite the spread, less than 19 per cent of Australians aged 15 to 50 have received a flu shot this year, as of June 22, according to the National Centre for Immunisation Research and Surveillance (NCIRS). That is well below the 55 per cent target for those under 65 years old. For COVID, about 771,000 vaccine doses were administered in NSW in the 12 months to June 11 and 2.6 million nationwide, according to government data.

Dr McCroary blames a mix of COVID fatigue and vaccine hesitancy for vaccination rates falling behind. A survey by NCIRS also found time constraints, access, and cost-of-living pressures are contributing factors.

The immediate solution to this shortfall is not clear, but Dr McCroary said one measure that may help is a combined COVID-flu vaccine. The concept of a combination vaccine is straightforward — one shot to cover multiple threats. It's also not without precedent.

The measles, mumps, rubella, and varicella (MMRV) vaccine has long been an effective standard in childhood scheduling, while modern flu doses are designed to protect against multiple strains. In its latest vaccination strategy, the federal government flagged combination vaccines for respiratory diseases as one possible pathway to increasing immunisation rates.

No dual vaccine for COVID and influenza has been approved for use across the world, but developers and researchers are in pursuit of a combination shot. In phase 3 human trials, both Moderna and Pfizer's mRNA iterations have reported positive results.

There currently is no clear date for rollout, with Moderna last month withdrawing its regulation submission to the Food and Drug Administration (FDA), citing pending efficacy data of a separate flu vaccine as the reason. But even when these vaccines do become available, one difficulty on the horizon could be administration.

Research published in the Medical Journal of Australia earlier this month found administering influenza and COVID vaccines together could reduce hospitalisations in the latter. But COVID's erratic nature alongside vaccine antibodies waning after six months means the risk of infection and transmission are heightened if cases spike beyond that window.

Still, the upside of a future combined vaccine lies in its ability to improve coverage. A persistent issue that health workers like Dr McCroary are dealing with now. 'With your health, talk to health practitioners, talk to your GP,' he said. 'I'm still writing death certificates for COVID and influenza during this season because we expect that infection numbers will be going up again now.'