[katieHaylor (OP)]

Ian says:

I read worrying reports about Australian flu and its possible impact on the northern hemisphere this winter. I also read that there is considerable uncertainty whether flu vaccinations now being administered will be effective against it. Other reports suggest the virus responsible for Australian flu might have mutated since the current vaccine was formulated.

Why is there such uncertainty? Surely the virus is being tracked and it is known whether it has mutated and rendered the vaccine ineffective?

What do you think?

[evan_au]

It looks like this thread was hijacked by a discussion of Thimerosal (a preservative used in vaccines).

the virus responsible for Australian flu might have mutated since the current vaccine was formulated.

Most viruses mutate fairly rapidly, because there is no real proof-reading when their genetic code is copied.

However, influenza has an additional built-in mechanism for sudden, big genetic changes, which is genetic reassortment.

Influenza vaccine typically takes about 6 months to produce and distribute, so identifying the specific virus strains which are going to cause problems in 6 months time requires an educated guess. The particular strains to include in the vaccine are recommended by a UN/WHO committee.

Fortunately, this committee can obtain some hints from the flu strains circulating in winter in the opposite hemisphere's winter; some of these are likely to cross the equator and start to circulate in the other hemisphere as the temperature grows colder. The WHO selects typically 3 or 4 strains to include in the next vaccine.
https://en.wikipedia.org/wiki/Influenza_vaccine#Annual_reformulation

The flu vaccine formulation is often slightly different in the northern and southern hemispheres, but in this case, they look the same (there was a change from a California strain to a Michigan strain in the 2017 Southern formulation).
Southern-hemisphere 2017 Vaccine (Winter started around May 2017)
- A/Michigan/45/2015 (H1N1)pdm09-like virus
- A/Hong Kong/4801/2014 (H3N2)-like virus
- B/Brisbane/60/2008-like virus
- B/Phuket/3073/2013-like virus

Northern-hemisphere 2017/2018 Vaccine (Winter starts around November 2017)
- A/Michigan/45/2015 (H1N1)pdm09-like virus
- A/Hong Kong/4801/2014 (H3N2)-like virus
- B/Brisbane/60/2008-like virus
- B/Phuket/3073/2013-like virus

See: https://en.wikipedia.org/wiki/Influenza_vaccine#Annual_reformulation

There are some newer methods of producing flu vaccines that might take a shorter time to reach volume manufacture. This may in future allow for a more-informed educated guess, and still produce enough doses for the start of the flu season.

[Colin2B]

I’ve moved the highjacked parts of this thread into ‘That Can’t Be True’ section.

[chris]

The "vaccine effectiveness" of flu vaccines is cited as 75%. In practice, what this means is that, at least 75% of the time, administering flu vaccine to an individual will protect them during the current flu season. It is not 100% for the reasons highlighted above: flu vaccines are a "best guess" at what strains will be circulating in about six months' time - the virus many mutate more rapidly than anticipated, or new mutants may emerge that are not covered by the selected vaccine strains; there are also differences in individual human responses to the vaccine - some people will fail to mount an effective response, which happens for a range of reasons including age and immune status.

Overall, flu vaccine is judged to be cost-effective and safe. These results are based on significant bodies of data from many countries and collected over many years. The benefits are also quite clear for medical and healthcare workers. Vaccination reduces secondary cases in both staff and patients, and significantly cuts staff absence owing to sickness over winter.

[smart]

@chris - What do you think about this: https://www.sciencedaily.com/releases/2009/05/090519172045.htm

[evan_au]

They found that children who had received the flu vaccine had three times the risk of hospitalization, as compared to children who had not received the vaccine.

It is possible that children who had severe (life-threatening) asthma had very high rates of immunisation, while those with mild asthma were not so likely to be vaccinated.

If the vaccine is 75% effective, that is 25% of severe asthma sufferers who would have been infected. These patients are far more likely to end up in hospital than those who had mild asthma, and were probably not vaccinated.

It is also significant that the study was conducted in the USA, which doesn't have a public hospital system in the sense that most Western countries do (ObamaCare would have brought the USA closer to the health standards of other countries - but now unlikely). In the USA, poor people can't afford medical care, and often opt out. It is the rich that can afford immunisation, and can also afford to take their children to hospital if they are sick. The poor can't afford vaccination or hospital care unless it is life-threatening.

This is why a randomised double-blind experiment is the "gold standard" for medical studies, rather than looking back at what actually happened, driven by external factors like income.

[chris]

We made this informational mini-podcast about flu and flu-vaccines and released it as an "in-short" episode this week, which some people might find interesting to listen to.