Leading article: Medical proof that aid saves lives

Immunisation has changed the world. It has saved more lives than pretty much any other public-health programme in modern history. Mass killers such as smallpox have been eradicated. Others such as polio are close to extinction. Some 80 per cent of children in the world are vaccinated.

But tens of millions on our planet have still not been reached by the immunisation revolution. Preventable diseases such as pneumonia and diarrhoea are still responsible for around one million child deaths a year in the developing world. The Global Alliance for Vaccines and Immunisation (Gavi), which will hold a fund-raising conference in London today, aims to close that lethal gap.

Gavi, an umbrella organisation comprising charities and multilateral relief agencies, has immunised 288 million children over the past decade. This has saved an estimated 5.4 million young lives. It hopes to immunise 243 million more children in 72 countries by 2015 and avert a further four million deaths. To this end, Gavi is now seeking to raise £2.3bn from developed countries. Our own Prime Minister, David Cameron, has pledged that Britain will make a significant donation, made possible by the Coalition's agreement to increase the Department for International Development's budget. That commitment is welcome. And it needs to be matched by other governments.

But are Gavi's methods cost effective? Pharmaceutical firms have said that they will sell vaccines to Gavi at reduced prices. But Daniel Berman, the deputy director of the Médecins Sans Frontières charity, has argued that the prices charged by pharmaceutical companies are still too high and that Gavi should be driving a tougher bargain when it purchases vaccines. It is a legitimate debate. Any money saved in this way can be used to distribute more vaccines. Governments have a responsibility not only to donate to Gavi but also to press it to be as efficient as possible.

But what Gavi's history shows is that well-targeted aid for the developing world can, despite what the sceptics say, be effective in saving lives. And what should also be beyond doubt is that mass vaccination is the right medicine for the planet.