The single most effective medical intervention EVER is the vaccine.

More than antibiotics, more than surgery, vaccines have saved millions of lives. With the brand new Ebola vaccine showing promising results in clinical trials, it is a good time to celebrate the vaccine and the role each of us play in global health.

For many of the world’s big challenges – war, poverty, disease – I often feel depressed by the lack of difference I could realistically make. Like throwing a grain of sugar to try and knock down a brick wall.

But When it comes to vaccines, each one of us plays an absolutely critical role.

This is because of Herd Immunity. For any vaccine to work, a large percentage of the population must be vaccinated to stop the disease being able to spread.

The percentage of people who need to be vaccinated varies from around 85 per cent to 92 per cent. That is a large chunk of any community and leaves room only for the weakest in our society – the tiniest babies who are not yet old enough to be vaccinated, people who are allergic to one or more of the ingredients and people whose immune systems are suppressed.

It is just impossible for people to choose not to vaccinate and still expect their children to be safe. When we check whether we need a booster or get our children vaccinated we are making a life saving decision not only for ourselves but for our friend’s newborn baby and our relative who has cancer.

It is a clever choice we can all be proud of.