Everything we do in life has a degree of risk associated with it. So to consider the risk of immunisation it's useful to think about risk in other areas of our lives.

In this way we can compare the likelihood of something going wrong when a child is immunised, with the likelihood of suffering other misfortunes in life.

For example, every time you get into a car, you are taking a risk of being involved in an accident. In 2001, almost 5,000 children were killed or seriously injured on the roads in Great Britain.

The risk of a child pedestrian being involved in a road accident rises significantly at the age when they start school and children between 11 and 15 are most at risk of being killed or seriously injured as pedestrians or cyclists. (Source: Dept for Transport)

If you catch the measles disease, the risk of convulsions is 1 in 200 people with the disease.

So when you look at the relative risks of immunisation, it is important to remember that an unimmunised child is at greater risk of catching measles, one of the most infectious diseases there is and one which can cause serious complications or even death.

It's difficult to calculate the exact risk of a child catching measles because it will vary according to the level of immunity in the child's community and how much they travel outside of that community.

So why do people worry?

It's partly to do with the amount of control they feel they have. When you drive a car for example, although there's a relatively high risk of something going wrong, you feel confident that you are in control.

But with immunisation, you can only decide to immunise (combined or mono component vaccines) or not to immunise, you know you cannot control any possible adverse effects.

Then there's the question of choosing to do something to your healthy child which is unpleasant - giving them an injection - in order to protect them against a disease that, thanks to immunisation, most people no longer see.

The benefits of immunisation are invisible to you - you will not see your child become ill with measles; you will not see your child affected by polio; they'll not get meningitis C.

In this way immunisation is very different from giving a child a medicine to make them better when they are already unwell.

So some people may find it tempting to 'leave it to nature'. However, deciding not to have your child immunised means putting them at risk of catching a potentially serious illness.

The bottom line

The bottom line is simple: having the vaccine is safer than not having the vaccine, whether for individual people or for whole populations.

The vaccines used in the recommended immunisation schedule have been very carefully tested. They are used in many countries besides the UK.

We know they are not 100% effective in every individual, but they're the best defence we have against epidemics that used to wipe out or permanently damage large numbers of people.

The smallpox vaccine wiped out smallpox. Polio vaccine is well on the way to doing the same to the polio virus: an incredible achievement.
We now have the opportunity to do the same with other viruses and bacteria, protecting our children and future generations.