Influenza is a highly contagious viral infection that can cause severe illness and life-threatening complications, such as pneumonia and bronchitis. Unlike the common cold, which gradually develops, influenza symptoms begin abruptly and may linger for weeks.

Influenza remains the leading cause of vaccine-preventable disease in Australia and costs the Australian healthcare system at least $85 million per year. It is estimated that influenza contributes to an average of 13,500 hospitalisations and more than 3,000 deaths among Australians aged over 50 each year.

There are three types of influenza virus that infect humans: influenza A, B and C. It is thought that only influenza A and B are responsible for major outbreaks and severe disease. Influenza A is typically more severe and peaks earlier in the season than influenza B. Furthermore, influenza B primarily affects children.

The World Health Organization (WHO) meets in September each year to make recommendations on the strains to include in the Southern Hemisphere seasonal influenza vaccine. The Australian Influenza Vaccination Committee (AIVC) and Therapeutic Goods Administration (TGA) review these recommendations before the TGA decide on the vaccine composition for the following year.

For the 2016 influenza season, WHO recommends the following three strains for inclusion in the manufacture of influenza vaccines:

  • A/California/7/2009 (H1N1)pdm09-like virus
  • A/Hong Kong/4801/2014 (H3N2)-like virus
  • B/Brisbane/60/2008 (Victoria Lineage)-like virus

The additional optional strain (to be included in quadrivalent vaccines only) is:

  • B/Phuket/3073/2013 (Yamagata Lineage)-like virus

In 2016, the National Immunisation Program (NIP) will only provide quadrivalent influenza vaccines instead of the usual trivalent vaccine. Two age-specific influenza vaccines will be provided free of charge to eligible groups under the NIP as shown in Table 1. Both trivalent and quadrivalent influenza vaccines will be available for purchase on the private market.

Table 1. Influenza vaccines available in Australia for the 2016 season

Brand Type Age Group National Immunisation Program
Fluarix® Tetra Quadrivalent >3 years Yes
FluQuadri Quadrivalent >3 years No
FluQuadri Junior Quadrivalent 6 to 35 months Yes
Fluvax® Trivalent >5 years* No

*Fluvax® should only be used with caution in patients aged 5 to 9 years.

Quadrivalent influenza vaccines were available in 2015, however, were not funded on the NIP. These vaccines included a second B strain to ensure that both lineages were covered. The benefit of this additional strain is unpredictable and depends upon the level of circulating B strain in the community. Some studies demonstrate that the additional B strain found in quadrivalent vaccines only accounted for between 0% (in 2000 and 2001) and around 30% (in 2008) of all circulating influenza strains. In addition, in 11 out of 15 years, the optional B strain has accounted for less than 5% of typed influenza cases.

The Australian Technical Advisory Group on Immunisation (ATAGI) recommends the use of quadrivalent influenza vaccines in preference to trivalent vaccines. However, ATAGI also advocates that trivalent vaccines are an acceptable alternative, particularly if quadrivalent vaccines are not available.

Fluvax®, the trivalent influenza vaccine manufactured by Seqirus, is anticipated to be the first influenza vaccine released to the Australian market in 2016. It is expected to be readily available in March, whereas the quadrivalent Fluarix® Tetra (GlaxoSmithKline) and FluQuadri (Sanofi Pasteur) may not be available until April or May.

It is important to note:

  • Early vaccination is most effective against influenza
  • The additional B strain found in the 2016 quadrivalent vaccine was included in the 2015 trivalent vaccine
  • There is the potential for some cross-lineage protection against the non-vaccine B stain

Given the uncertain additional clinical benefit of the quadrivalent vaccine over the trivalent vaccine, those seeking vaccination are recommended to use Fluvax® in preference to delaying vaccination in the event of a supply interruption. Delaying vaccination may reduce vaccination rates and lead to increased rates of influenza infection and serious complications.

References:

  1. Department of Health. Immunise Australia Program. Canberra: Australian Government, 2016.
  2. Department of Health. New flu protections following high season: media release statement. Australian Government, 2015.
  3. Department of Health. The Australian Immunisation Handbook (10th Edition). Canberra: Australian Government, 2015.
  4. Heikkinen T, Ikonen N, Zieglar T. Impact of Influenza B lineage-level mismatch between trivalent seasonal influenza vaccines and circulating viruses, 1999-2012. Clin Infect Dis. 2014; 59(11): 1519-24.
  5. McElhaney JE, Palache AM, Wilschut JC. Rapid Reference to Influenza. Elsevier, 2006.
  6. Mclean HQ, Thompson MG, Sundaram ME, Kieke BA, Gaglani M, Murthy K, et al. Influenza vaccine effectiveness in the United States during 20212-2013: variable protection by age and virus type. J Infect Dis. 2015; 211(10): 1529-40.
  7. Melbourne Vaccine Education Centre. Quadrivalent Influenza Vaccine 2015: MVEC position statement. 2015.
  8. Victorian Infectious Diseases Reference Laboratory. VIDRL Annual Reports (2012-2014). North Melbourne, 2013 – 2015.

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