Got a quote from my epidemiologist friend which may or may not be of use (it's a bit lengthy, but I found it really interesting):
"No vaccine is entirely safe, but the latest stuff about it being able to give you flu is totally untrue. The vaccine used in the UK (and North America and many other countries) is made out of three types of killed virus. Flu virus is pretty fragile, there is no chance it is alive, and even if it were, it would be pretty hopeless at infecting humans.
At a personal level, you already know that I got vaccinated for the first time this year. The feeling among those of us who obsessively watch the lab reports is that a big wave of H3N2 fujian-like influenza is about to hit the UK (in fact, wouldn't be surprised to see it in the report this Wednesday, given some of the local school outbreaks we've had already). The vaccine will only be partially effective against this strain. What `partially' means here is not clear, it may be enough to entirely protect some people, and when it doesn't, I suspect it will reduce symptoms and/or shorten infection. I'm not a medical practicioner, but I would urge my friends to seriously think about getting vaccinated, especially if they come into conctact with anyone at risk (the very young, the very old, and those with certain medical conditions like asthma).
The WHO factsheet is quite useful, though a little conservative on the annual death rate I think:
www.who.int/mediacentre/factsheets/2003/fs211/en/index.html
In measles, the attitude that it is best to get infection as a kid and allow immunity to happen naturally would mean of the order of a thousand measles deaths per year at present day in the UK if there was no vaccine in use. So I feel the same way about such an argument with regard to flu - this is something we can live without. I think that there is something unnatural about these epidemics anyway, they persist through our population being clustered in large towns and cities. Flu would never have been an issue in prehistoric times. The fact is that the world is as it is, and flu has the chance to perpetually circulate and mutate. We'd be mad not to try protect ourselves."
and later she said:
"Quite how "effective" the flu vaccine is depends on the vaccine strain and the circulating strain. If there is a close match, then the vaccine is near perfect for everyone. The problem is that there other other viruses that cause colds and other infections that seem like flu, so it gets said that the vaccine has failed.
There are "antigenic shifts" or changes in "subtype" where half of the virus genome comes from influenza in another species (aquatic birds, possibly via chickens). This happened in 1918, 1957 and 1968. There have been smalled outbreaks of alien types recorded recently, but they didn't transmit that well (but were deadly to many).
Then there is the normal gradual mutation of influenza ("antigenic drift", but of course its not that simple either, it turns out that this mutation isn't that smooth and gradual, sometimes there are bigger steps than others (e.g. this Fujian-like strain that is emerging now).
The vaccine will still be of some use in years like this year. Anti-viral drugs should work just fine (but everyone takes them too late, or can't get prescribed them). The current vaccine would be useless in the case of a subtype shift (like 1918), but scientists aren't idle on this one.
You might as well not bother if you don't mind being horribly ill for a week or so, and you don't mind the risk of it leading to something worse, and you don't mind the risk of infecting people around you, some of whom may have serious complications. It is up to you, and there isn't enough vaccine to cover the whole population anyway.
It is possible to get flu every year, and there are some who seem to never catch it. We have some idea as to what might be behind this. It might be down to something called MHC type. (You remember there were stories of some people who never caught HIV despite having high exposure? Well that was the same thing.) This is something I'm working on at the moment."