If you’ve wondered whether a flu shot is a bit of a lottery, you might be right.
Following the devastating 2017 flu season, we’ve learnt that the way authorities decide on vaccination formulations can be a bit of a lottery.
Next year’s Australian flu vaccine will borrow characteristics from viruses isolated in 2013, `15 and `17, the latter being the year of the most catastrophic influenza infection rate since the 2009 swine flu pandemic.
The ‘picks’ are made by the World Health Organisation (WHO), which estimates which flu strains are most likely to be circulating ‘Down Under’.
In 2017, visits to hospital by patients suffering with flu soared 50 per cent. More than 221,000 flu infections were recorded around the nation – the highest ever – and many who fell sick had had a flu shot.
The nasty flu season rang alarm bells for health authorities, who determined that standard vaccines were probably not particularly effective in the elderly.
Of the six different vaccines offered last year, two had immunity-boosting properties and were tailored especially for people over 65.
The WHO’s recommendations of the combination of strains to be covered during the southern hemisphere flu season are vetted by the Australian Influenza Vaccine Committee (AIVC). The committee then then passes them on to the Therapeutic Goods Administration (TGA) for consideration.
This week, the TGA accepted the 2019 recommendations.
“Influenza vaccines can change from year to year as new strains of influenza virus appear,” according to the TGA. “This is one reason vaccination against influenza is given every year.”
In coming to its latest decision, the TGA “reviewed and evaluated data related to epidemiology, antigenic and genetic characteristics of recent influenza isolates circulating in Australia and the southern hemisphere, serological responses to 2017-2018 vaccines, and the availability of candidate vaccines viruses and reagents”.
There are two groups of flu viruses, A and B. The B viruses have two main strains while the A virus has more mutations. A strains are generally targeted with the vaccine H1N1, which was formulated after the 2009 pandemic, and H3N2, which evolved from a Singapore isolation.
The recommended strains for 2019’s vaccine combinations are base on:
- a H1N1 virus isolated in Michigan in 2015
- a H3N2 virus isolated in Switzerland in 2017
- a B virus isolated in Colorado in 2017
- a B virus isolated in Phuket in 2013, and
- a H3N2 virus isolated in Singapore in 2016.
The 2018 combinations excluded strains isolated in Switzerland and Colorado, but included a virus isolated in Brisbane in 2008.
In the devastating year of 2017, one of the vaccines available covered the Brisbane and Michigan strains, plus a H3N2 Hong Kong strain from 2014. The second flu jab covered only the 2013 Phuket strain.
The WHO recommends vaccination combinations many months, and sometimes up to seven months, before a flu season kicks off. The danger is that it may incorrectly guess the strains that will actually become more widespread and fail to recommend appropriate cover.
This is what happened in 2017 with the H3N2 strain, which has mutated many times since it was isolated and continued to do so even as production of vaccines was under way.
“The recommended composition of influenza vaccines for Australia in 2019 introduces a new H3N2-like virus strain and new strain for the B Victoria lineage when compared to the composition of the trivalent and quadrivalent vaccines for Australia in 2018,” the TGA said.
Let’s hope the WHO has picked some ‘winners’ this year.
Will you be getting a flu shot next year? How much confidence do you have that it will protect you against influenza?