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Celebrating Five Years of the Doherty Institute

Viral Infectious Diseases

Record years of influenza in Australia

If you had influenza, or the flu as it’s more commonly known, in 2017 or 2019, you made it into the history books. In 2017, 251,147 people in Australia were confirmed as having the flu, and 304,593 in 2019, compared to 90,860 in 2016 and 58,856 in 2018.

“2017 and 2019 were record years for influenza in Australia,” says Professor Kanta Subbarao Director of the World Health Organization (WHO) Collaborating Centre for Reference and Research on Influenza at the Doherty Institute.

“These seasons were as big as the pandemic in 2009.”

Contracted by the Commonwealth Government, the role of the Collaborating Centre is to identify what viruses are causing influenza and whether they are similar to virus strains included in the yearly flu vaccine. They also have a team participating in a consortium that looks at vaccine effectiveness in real time during the flu season. 

“In Australia, overall vaccine effectiveness in 2017 was very low at 33 per cent, while early estimates for 2019 suggest that vaccine effectiveness was relatively high for most types and subtypes, except for H3N2, which was a bit lower,” says Professor Subbarao.

The Centre is one of five such Centres around the world – Atlanta, Beijing, London and Tokyo – that make recommendations to the WHO as to which viruses should be included in the annual vaccine ahead of the upcoming northern and southern hemisphere influenza seasons.

According to Professor Subbarao, 2019 was very unusual in that there were a series of events that contributed to the record number of cases. Between December 2018 and February 2019 in what is generally considered the ‘interseasonal’ period, there were more than 20,000 cases of influenza caused by influenza A H1N1 viruses.

“We always expect to see some influenza in the summer, but this amount of influenza activity was unusual,” says Professor Subbarao.

2017 was quite a different story.

“We had a very intense season and severe disease. The numbers are nearly the same as 2019, but in 2019 we didn’t see the same sharp peak,” says Professor Subbarao.

So why was the 2019 season so long?

“There are prevailing theories, the first of which is that the early start to the season could have been because we had a mild 2018 season, so perhaps there was not enough immunity in the population,” explains Professor Subbarao.

“The second is that we had introductions of viruses from overseas into a relatively nonimmune population and they took off.

“People are also speculating about a change in weather patterns. But it may just be the nature of the seasonality of influenza – we don’t know how it’s going to behave.”

Through her research program, Professor Subbarao is looking to see whether the annual seasonal flu vaccine can be improved. Specifically, she’s focussed on understanding whether the timing of the administration of the vaccine and manufacturing in eggs has an effect on the immune response, and how long the antibodies last post vaccination.

Meanwhile, Associate Professor Sheena Sullivan and Dr Annette Fox, also of the Collaborating Centre, and Associate Professor Adam Kucharski from the London School of Hygiene & Tropical Medicine, were awarded a five-year, USD$4.16 million grant by the National Institutes of Health in 2019 to investigate the possible negative consequences of repeated flu vaccinations, specifically in healthcare workers.

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