Are vaccines bad for you?

Chris Smith took on this infectious enquiry from caller Richard. 

Chris - First of all, thank you for an interesting question Richard. The flu vaccine in an average year is about 75% effective. Now what that means is that if you take an average person, with an average dose of flu, and an average dose of flu vaccine, they’ll be protected 75% of the time. But flu isn’t just one single entity, there are many different strains of flu. There’s two different types of flu A: there’s H1N1 swine flu and there’s also H3N2, and there’s also another form of human flu called flu B. All of them can cause epidemics and all of them are represented in the vaccine. All of them continuously mutate and change and, therefore, you have to update the vaccine year on year on year. You have to keep having the vaccine every year in order to make sure your immunity stays current.

Now, the other problem with this is that not every years the vaccine is 75% effective. Some years the vaccine may not be as effective as others. This year has been a particularly bad year for the flu vaccine. In fact, one of the types of flu that was in the vaccine - the B strain - didn’t actually work at all because the virus had mutated. And changed and the other type of flu A - the H3N2 - that was in the vaccine, that didn’t work very well either; it was about 20% effective for various reasons.

So, therefore, people who had had the flu vaccine this year were protected against one of the circulating strains but not the other ones. And that meant that they might go around thinking that they’re protected from flu and it’s not going to be a risk for them and for anybody else and, therefore they’re more likely to be spreading flu.

There was an interesting study that got done by the British Medical Journal about 10 - 15 years ago - it got published in the British Medical Journal - and what they did is to ask people “have you had flu this winter?”. And then they took samples from those people and tested their blood for antibodies against the flu and what they found is about half the people who said they didn’t have flu that year, had had flu as proved by the antibodies that were in their bloodstream.

In other words, you can probably get people who have a low level infection with flu. They don’t know that they’ve got it. They don’t feel ill because they’ve got partial immunity to the flu but they’re nonetheless fully infectious and they go about their business potentially infecting other people and spreading flu around, and they don’t know they’ve done it.

One the whole summarising: flu vaccines are very good; they’re money well spent; they do save lives and the help to protect patients in hospitals and care homes and they help to protect kids in schools. They help to protect people with serious illnesses like diabetes, kidney disease, heart disease and so on. But, at the same time, we have to make sure everyone has one because otherwise you’re leaving a gaping gap in our defences. And anyone who hasn’t been vaccinated then catches the flu and then they’re fully infectious and they give it to other people.

So it is effective; we do like the flu vaccine but, at the same time there has to good compliance and uptake in the population or it’s not going to work.