The influenza vaccine has just become available (March 10), but there’s no need to panic.

Influenza is certainly being reported (up 1.7 times on the same period last year) but still at low levels. A high number of cases were reported last year but this was seen as catch up for the low infection rate during the pandemic. The USA has experienced a moderate flu season this year (October to March).

Influenza rates generally peak between June and September in Australia. Often there is a small upturn in flu in the inter-seasonal period in March/ April when university students arrive from the northern hemisphere winter, bringing the flu with them.

A recommendation on the composition of the southern hemisphere influenza vaccine is provided by WHO in September each year, and is usually based on the experience of the previous season in the northern hemisphere. It is then up to national authorities to approve this formulation. There is a change to the vaccine composition this year (2024).

What is the flu vaccine?

Only quadrivalent influenza vaccines will be available in Australia for the 2024 season. There are 2 types, egg-based and cell-based. Each has 2 strains of Influenza A (H1N1, H3N2) and 2 strains of B in the vaccine.

Both types of vaccine are available under the National Immunisation Program (NIP). The NIP provides free influenza vaccines to those at most risk of serious disease.

A stronger flu vaccine is available to those 65 years and older. Older individuals may not be as responsive to vaccines as younger people. This is called immune senescence. It is also why diseases like influenza and COVID-19 are more likely to cause serious illness in this age group. The over 65 years flu vaccine has more of the antigen than the standard vaccines, though the composition remains the same. This should provide a better stimulus for antibody production.

Corporate flu programs need to be aware of the difference and make sure the older worker is given the appropriate vaccine.

Who should receive the flu vaccine?

Everyone, 6 months and over is recommended to get a flu vaccine each year, but only 30-35% people are vaccinated. Coverage is much greater in those over 65 years than in the young age groups.

It is strongly recommended for certain groups to be vaccinated. These groups will receive the vaccine for free under the NIP.

How effective are flu vaccines?

The effectiveness of the flu vaccine varies from year to year. It really depends on how close in structure the vaccine to the circulating strains. Sometimes it is very close and at other times not so good. It is generally accepted that the effectiveness ranges from 40%-60%. The vaccines work better against the B strains of the virus and the H1N1 of the A strain but not so well for the H3N2 strain. It then depends on the predominant strain for the season to determine whether the vaccine was effective for the season.

A study of the 2019-2020 season (pre-pandemic) in the USA showed that vaccination prevented 7 million influenza-related illness, 3 million clinic visits, 100,000 hospitalisations and 7,000 deaths.

Influenza vaccine and travel.

People often confuse a common cold with flu. “Colds” are due to several viruses which have a similar clinical picture. Colds are common, hence the name “common cold”. They are generally annoying rather than disabling. Fortunately, influenza isn’t common, but it can be very unpleasant. A bout of influenza can last for several days. The symptoms can include fever, chills, dry cough, headaches, and severe fatigue. It is also highly contagious. If you are a member of travelling group, you might be the index case for the group and the start of a holiday from hell. It might also be a particularly important holiday, a honeymoon or a 30th wedding anniversary; or an important business trip. It is always important to consider the flu vaccine if there is something you would prefer not to miss!

The flu vaccine is the first vaccine you should consider in the context of travel. Influenza is the most common health issue which can be prevented by vaccination.

Flu vaccination should never be considered in an age-based context when travelling. It is true that a person aged 20-40 years is less likely to experience serious illness, hospitalisation, or death but they also have something to miss!