10 flu vaccine facts to know

20:31, Aug 19 2014
10 flu vaccine facts to know
GOT THE BUG? The flu vaccine can only offer about 50 to 80 per cent protection from the flu. But that's certainly better than nothing.

Had the flu vaccine, but still sick? Here are 10 flu mysteries explained...

The flu vaccine saves millions of people a year from the clutches of flu, but it doesn't make us bullet-proof. If you're confused about how it works, if it works and whether it even triggers the flu, stick with Stuff while we unravel the mysteries.

10 things you should know about the flu vaccine 

1. It's not perfect.

Depending on the season, the influenza vaccine is between 50% to 80% effective in preventing flu illness. Last year it was just over 50% effective for the overall population. Its effectiveness varies due to the age and immune competence of the person being vaccinated, and due to the 'match' between the virus strains in the vaccine and those circulating in any given flu season.

2. 'Antigenic drift' makes things tricky. 


The flu virus changes or mutates as it travels around the world - a process called 'antigenic drift'. Minor changes in a virus can mean that the match between the circulating virus and the flu vaccine (prepared months in advance) might not be as close as forecasted.

The good news is that the Influenza A H1N1 virus - predominantly in circulation this year - hasn't undergone any genetic changes resulting in antigenic drift, which means it's still a close match to the H1N1 strain included in this year's flu vaccine composition.

3. Flu vaccine is our single best protection. 

Medical experts agree that even at 50% effectiveness, the seasonal influenza vaccine is still our best protection from the flu, and from secondary complications of the flu. It is most effective in children and mid-life adults. And, the more people vaccinated, the less chance there is for flu to spread, so protecting yourself from the flu can also protect the more vulnerable people around you.

4. How long does it take for the vaccine to work?

The vaccine takes up to two weeks to provide protection from the flu strains covered. So if you're exposed to one of the strains just before or during the two-week period, you might still catch the flu.

5. Can you get the flu from having the vaccine?

No - the vaccine itself can't give you the flu because it contains no live viruses. The seasonal influenza vaccine contains fragments of the virus that stimulate your immune system into producing antibodies against the virus. 

6. A mild reaction to the vaccine is not 'the flu'.

The vaccine will stimulate an immune response which can result in redness at the site of injection. In rare cases, it may cause mild aches and pains, even a mild fever, for up to a day or two - but these shouldn't be mistaken for the flu.

7. Can you get sick, despite having the vaccine?

Yes - but the reasons are varied. There are viruses present every year that aren't covered by the flu vaccine, so you might catch a different respiratory infection with 'flu-like' symptoms around the same time as the vaccine is given. 

Some people are also more susceptible to flu due to underlying medical conditions. Generally speaking, some elderly people or people with chronic illnesses might develop less immunity after vaccination than healthy adults and children. But it's for these susceptible individuals that the vaccine is especially recommended, because it offers a level of protection they otherwise wouldn't have.

8. If you're fit and healthy, do you need the vaccine?

Being fit and healthy doesn't protect you from the flu. While all of us are built differently - some with inherently strong immune systems - there are periods in life when we're all exposed to flu viruses. For example, being around children or schools (where viruses love to spread) can alter your susceptibility to the flu, even if your immune system is 'strong'.

9. Is the vaccine a good idea for pregnant women?

Yes. The flu vaccine is strongly recommended for pregnant women. In fact, maternal influenza vaccination is significantly associated with reduced risk of flu infection and hospitalisation for influenza-like illness in infants up to six months of age.

10. Do you need the vaccine every year?

Immunity to the strains in the flu vaccine lasts up to a year after vaccination. The changing nature of flu viruses means that new flu strains are constantly appearing and the flu vaccine has to be altered accordingly. So in order to be protected from newly emerging strains, you need to get vaccinated every year.

- Let us know if you're still stumped, and if you've had the flu vaccine this year, tell us how it's worked for you.