Influenza vaccination; it's not too late!

Change in Influenza epidemiology depicts increased risk for children and young adults.

Influenza notifications are increasing with high local activity in the Hunter New England and Central Coast area (1). When compared to previous influenza seasons, a peak in August is anticipated (2). Children and young adults are considered a major driver of transmission, especially as they have high levels of socialising in schools and early learning facilities, and then may transmit the virus to vulnerable family members.

At the beginning of the 2023 influenza season, the majority of notifications were Influenza type A (1). However, this trend has been shifting and the proportion of Influenza B cases in NSW has been increasing much earlier than in previous years, overtaking numbers of Influenza A notifications in June.

Source: NSW Respiratory Surveillance Report, week ending 15.07.2023

Influenza B is known to impact younger populations more heavily causing more severe disease (3, 4, 5). The increased prevalence of Influenza B cases increases the risk of children to contract Influenza B and therefore, subjecting them to a higher risk of developing severe influenza, and increasing the risk of hospitalisation and adverse outcomes. Unfortunately, there have been reports of influenza associated deaths in children recently, including one case from the Central Coast.

The 2023 Influenza Vaccination gap

It is not too late to get vaccinated against Influenza, as the Influenza season usually last through to October. As a spike in cases is expected in the next month, it is particularly important to promote Influenza vaccinations now. The PHN has launched videos on social media to promote influenza vaccinations to the public.

2023 vaccination rates for influenza among children, alike all other age groups, are lower than in previous years and it is vital that providers support access and timely vaccination efforts to close the gap. ATAGI recommends influenza vaccination for all children over 6 months of age, and vaccination is considered the most effective measure to prevent influenza. Influenza vaccination is free for children between 6 months and five years of age (6). The influenza vaccine is also free for First Nations people over 6 months of age, as well as all individuals aged 5 years or older with medical risk factors, pregnant women and people aged 65 and over (6).

2023 influenza vaccine efficacy and matching

While it is too early to assess vaccine effectiveness for this season, the good news is that of 1,915 samples referred to the WHOCC in the year-to-date, 97.4% of influenza A(H1N1) isolates, 82.8% of influenza A(H3N2) isolates, and 99.0% of influenza B/Victoria isolates characterised were antigenically similar to the corresponding vaccine components. This means that there is a high level of vaccine match (2), and therefor, a high likelihood that the influenza vaccine is very effective.

Sources:

1. NSW Health, 2023. NSW Respiratory Surveillance Report - week ending 15 July 2023
2. Australian Government. Department of Health and Aged Care, report no. 07, 2023. Australian Influenza Surveillance Report (health.gov.au)
3. University of Sydney, 2015. Surge in “type B” flu this winter - The University of Sydney
4. Australian Broadcasting Company ABC, 15.07.2023. Influenza deaths in Queensland and NSW prompt calls for free vaccine - ABC News
5. Sharma L, Rebaza A, Dela Cruz CS, 2019. When “B” becomes “A”: the emerging threat of influenza B virus | European Respiratory Society (ersjournals.com)
6. NSW Health. 2023 seasonal influenza vaccination information for immunisation providers. 02.06.2023. 2023 seasonal influenza vaccination information for immunisation providers - Immunisation programs (nsw.gov.au)