Flu Outlook for 2026

As healthcare professionals committed to the well-being of residents in aged care facilities across Australia and New Zealand, you are at the forefront of public health. With the 2026 influenza season on the (far) horizon, understanding the science behind flu vaccine selection, the implications of circulating viral strains, and the insight from the Northern Hemisphere is not just theoretical – it's vital for proactive planning and protecting our most vulnerable populations. This blog will clarify the complex global process and outline its implications for your important work.

Every year, choosing influenza vaccine strains is a complex global task, often called a race against a moving target. This ongoing effort is driven by the influenza viruses' quick ability to change.

Influenza viruses, members of the Orthomyxoviridae family, are primarily classified into three types: influenza A, B, and C. Their ability to evade the human immune system depends on two surface proteins: haemagglutinin (HA) and neuraminidase (NA). Antibodies target these antigens, and alterations in their structure can diminish existing immunity.

The most common form of viral change is antigenic drift. This involves small, continuous mutations to the HA and NA antigens, gradually producing new variant strains. While some cross-protection from previous immunity may exist, the cumulative effect of these small changes means a new vaccine is needed each year. This is the fundamental reason why a seasonal flu shot is required annually.

In contrast, antigenic shift is a significant and sudden change that can lead to the emergence of a new influenza A subtype. This can happen when gene segments are exchanged between influenza A viruses, often involving strains that infect both humans and animals (such as birds). An antigenic shift can produce a virus so different that most people have little to no existing immunity, with the potential to cause a worldwide pandemic. While both influenza A and B viruses undergo antigenic drift, only influenza A viruses are known to experience antigenic shift.

To continuously monitor these viral changes and select the appropriate strains for vaccines, a global collaboration known as the Global Influenza Surveillance and Response System (GISRS) functions as an intricate "assembly line" for public health. This network includes National Influenza Centres (NICs) in over 100 countries, such as Australia’s Doherty Institute and New Zealand's ESR. These NICs collect and test respiratory specimens, carrying out preliminary analysis to identify influenza viruses. Representative clinical specimens and isolated viruses are then sent to six WHO Collaborating Centres (WHOCCs) worldwide, including the one at the Doherty Institute in Australia, for more detailed antigenic and genetic analysis. These WHOCCs evaluate circulating viruses and the suitability of existing vaccine strains. Ultimately, Essential Regulatory Laboratories (ERLs) produce reagents and candidate vaccine viruses for manufacturing. This coordinated system acts as an "effective early warning system" for new viral changes.

The World Health Organisation (WHO) holds two technical consultations each year to recommend vaccine composition: one in February for the Northern Hemisphere (NH) season and another in September for the Southern Hemisphere (SH) season. For the SH 2026 season, the recommendation will be made in September 2025. This staggered cycle allows the Southern Hemisphere, which follows the Northern Hemisphere's season, to utilise the latest data on circulating strains.

For the 2026 season, the influenza vaccines available in Australia and New Zealand will be quadrivalent, meaning they are designed to protect against four inactivated influenza virus strains: two influenza A and two influenza B strains. This formulation is a public health standard, providing broad protection against the most prevalent circulating viruses. Beyond the traditional egg-based approach, manufacturing has evolved to include cell-based production methods, which can benefit individuals with egg allergies and potentially allow for faster production.

Crucially for aged care, we now have access to enhanced vaccines for older adults, such as the adjuvanted Fluad Quad in Australia and New Zealand, among others. These are recommended over standard-dose options for individuals aged 65 and above to enhance their immune response. This advice is vital for protecting your residents.

The circulation of influenza is a global phenomenon, and the viral patterns of the Northern Hemisphere significantly influence the upcoming season in the Southern Hemisphere. This connection is a well-established epidemiological fact.

Influenza epidemics in temperate regions show a clear winter pattern. While the Northern Hemisphere usually sees cases from November to March, the Southern Hemisphere's season runs from May to September. Human travel is the key connection between the hemispheres. As people from the North travel south, they can carry the dominant influenza strains that developed during the NH's previous winter. These strains then "seed" the upcoming SH flu season. Consequently, analysing the dominant strains and the severity of the NH season is essential for predicting the potential intensity of the next SH season.

Australia and New Zealand are active and essential members of this global surveillance network, with the WHO Collaborating Centre at the Doherty Institute analysing viruses from the Southern Hemisphere and New Zealand's ESR contributing local data to GISRS. This local involvement ensures that public health authorities are actively engaged in monitoring the evolution of viruses.

A fascinating point of divergence arose during the 2024-2025 Northern Hemisphere season: a singular, uniform viral ecology did not materialise.

• The United States faced a severe flu season, mainly caused by the H3N2 virus, a subtype often linked to worse outcomes, especially in older adults. The American experience included an unprecedented number of influenza-related deaths among children for a non-pandemic season. An important finding was that 90% of these fatal cases occurred in children who were not fully vaccinated.
  
  
• In contrast, parts of Europe experienced a milder season where the H1N1 virus was the main strain, but they still faced a complex and severe respiratory virus season with excess mortality mainly in adults aged 45 and over.
  
  

This lack of consistency means a straightforward forecast for Australia and New Zealand isn't possible at this stage. The main question for the Southern Hemisphere is which of these differing viral ecologies will establish itself and become the dominant circulating strain in Australia and New Zealand in 2026.

"Do we need to be concerned yet?" This is the crucial question, and the answer, based on global data and local expert views, is a subtle one: there is a clear and strong reason for caution, but not for panic.

It is not currently possible to make direct forecasts for the 2026 Australian and New Zealand flu season. Professor Patrick Reading, Director of the WHO Collaborating Centre in Australia, consistently stresses that predicting the severity of the upcoming season is impossible due to factors such as the dominant virus subtype and human behaviour. As winter advances in the NH and case numbers rise, experts will gain a better understanding of circulating strains, enabling more precise forecasts.

However, the most important concern is not just the virus itself, but also the condition of the host population. Australian and New Zealand experts have pointed out a widespread "immunity gap". Because of years of closed borders and public health measures during the COVID-19 pandemic, the Southern Hemisphere has not had a normal flu season since 2019. This long period of low viral activity means that immunity at the population level has decreased significantly, leaving many in the community, especially younger people, with limited protection from past seasonal infections.

For aged care residents, this "immunity gap" presents a strong case for a possibly severe flu season. Even if the dominant strain that appears is not inherently more virulent, a population with lower immunity could see more infections, hospital admissions, and serious outcomes. The return of international travel, especially from the Northern Hemisphere, might reintroduce various strains, including the high-impact H3N2 from the US. The combination of a severe strain and an immunocompromised population, such as older adults and those with underlying health conditions in your care, significantly raises the level of risk.

The high number of paediatric deaths in the USA, mainly due to Influenza A and with 90% of those children unvaccinated, is a serious warning. While this mainly concerns children, it highlights the severity of circulating influenza A strains and the crucial role of vaccination as the primary prevention measure. The European experience, with excess mortality in adults aged 45 and over, further shows the potential impact on older people. As one Australian expert aptly said, "it's always a bad flu season because it's hospitalising and killing people".

Based on this analysis, several recommendations are critical for preparing for the 2026 influenza season, with a specific focus on aged care residents:

• Prioritise annual vaccination: Annual influenza vaccination is the most effective way to prevent influenza and its serious complications
  
  
• Consider Co-administration and Broader Vaccination Programs: The UK's Winter 2025/26 Vaccination Program emphasises increasing vaccination rates to lessen the burden on urgent care, especially for flu and COVID-19. It highlights eligibility for COVID-19 vaccines for residents in care homes for older adults, all adults aged 75 and over, and immunosuppressed individuals aged 6 months and above. The program aims to align the start dates for adult flu and COVID-19 vaccinations (from 1 October 2025) to facilitate co-administration whenever possible. Regions are specifically encouraged to prioritise vaccinations for residents in older adult care homes and those who are housebound. Healthcare systems are also advised to pay special attention to RSV and other vaccinations, co-administering vaccines where appropriate and safe.
  
  
• Address Vaccination Barriers: Ongoing low vaccination rates are concerning, often caused by barriers such as cost, difficulty booking appointments, inconvenient hours, and inability to take time off work. Tackling these through tailored campaigns and improved access, particularly for housebound people via outreach services, is a vital public health goal.
  
  
• Reinforce Complementary Preventative Measures: Beyond vaccination, highlight good hand hygiene, focus on air quality and ventilation, and, most importantly, stay home from work or school when feeling unwell. For healthcare personnel, this last point is crucial to prevent onward transmission to vulnerable residents.

While the nasal spray flu vaccine, FluMist, received FDA approval in September 2024 for self- or caregiver administration for individuals aged 2 through 49, this option is expected to be available from the 2025-2026 flu season. While not directly applicable to older adults in your care, it represents an evolving landscape in vaccine delivery.

The 2026 flu season in Australia and New Zealand poses an increased risk of impact, influenced by the severe and varied Northern Hemisphere season and our own population's "immunity gap." For aged care and housebound individuals, this requires our full attention. Vigilance, proactive vaccination – particularly with enhanced vaccines for older adults – and strengthening comprehensive preventative measures are our best defences against a potentially tough season. Your role in enacting these strategies will be vital in safeguarding your residents.

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