AISR fortnightly report no. 13 – 12 September to 25 September 2022
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The Australian Influenza Surveillance Report (AISR) is compiled from several data sources used to monitor influenza activity and severity in the community. These data sources include:
- laboratory-confirmed notifications to NNDSS
- influenza-associated hospitalisations
- sentinel influenza-like illness (ILI) reporting from general practitioners
- ILI-related community level surveys
- sentinel laboratory testing results.
The AISR is published fortnightly during the influenza season, typically between May and October. Influenza activity updates may be published outside of the seasonal period.
It is important to note that due to the COVID-19 epidemic in Australia, data reported from the various influenza surveillance systems may not represent an accurate reflection of influenza activity. Results should be interpreted with caution, especially where comparisons are made to previous influenza seasons. Interpretation of 2020 influenza activity data should take into account, but are not limited to, the impact of social distancing measures, likely changes in health seeking behaviour of the community including access to alternative streams of acute respiratory infection specific health services, and focussed testing for COVID-19 response activities. Current COVID-19 related public health measures and the community’s adherence to public health messages are also likely having an effect on transmission of acute respiratory infections, including influenza.
A decrease in influenza-like-illness (ILI) activity in the community has been noted since July 2022.
In the year to date, there have been 224,565 notifications reported to the National Notifiable Diseases Surveillance System (NNDSS) in Australia, of which 818 notifications had a diagnosis date this fortnight.
The weekly number of notifications of laboratory-confirmed influenza in 2022 has decreased to below the weekly 5 year average since mid-July.
In the year to date, of the 224,565 notifications of laboratory-confirmed influenza, 305 influenza-associated deaths have been notified to the NNDSS.
Since commencement of seasonal surveillance in April 2022, there have been 1,784 hospital admissions due to influenza reported across sentinel hospitals sites, of which 6.8% were admitted directly to ICU.
The impact for the season to date, as measured through the rate of FluTracking respondents absent from normal duties and the number of sentinel hospital patients with influenza, is low to moderate.
In 2022 to date, people aged 5–9 years, children aged younger than 5 years, and people aged 10–19 years have the highest notification rates.
To date, 82.5% of notifications of laboratory-confirmed influenza reported to the NNDSS were influenza A, of which 94.4% were influenza A(unsubtyped), 0.9% were influenza A(H1N1), and 4.7% were influenza A(H3N2). Influenza B accounted for 0.2% of notifications, less than 0.1% were A&B co-infections, and 17.3% were untyped.
Vaccine match and effectiveness
Of the 2,509 samples referred to the WHOCC to date, 92.4% of influenza A(H1N1), 94.3% of influenza A(H3N2), and the six influenza B/Victoria samples, were characterised as antigenically similar to the corresponding vaccine components.
Vaccine effectiveness is a measure of the protective effect of influenza vaccines against influenza and its complications and is typically around 40–60%. Based on preliminary estimates from sentinel hospitals (FluCAN), vaccine effectiveness appears at the lower end of the moderate range in 2022.