It's rare a newspaper actually manages to kill people, but Sir David King believes the Daily Mail may pull it off.

I want to tell you three interconnected stories. The first is some of the best news you will hear all year; the last two are some of the saddest. But they are all about how science saves tens of millions of lives, and how the persistence of faith-based thinking kills – not just in the distant witch-burning past, but today, across the world and, yes, even in Britain.

When I first went to central Africa, I met a woman exactly the same age as me called Marie Abawede who had given birth to four children out in the rainforests. The first three had all died – of measles. Her last baby was sick, and she was convinced he had "the killer" too. "If he dies, I will die," she said, plainly, without tears. In the year 2000, there were 396,000 women like this in Africa, watching their babies waste away pointlessly. Today, the figure has fallen by an incredible 90 percent. There are only 36,000 such women today, and there will be fewer next year, and the next year, and the next year.

This is because of pure science, combined with political will. The World Health Organisation (WHO) has used funds donated by governments across the world – including ours – to massively ramp up measles vaccinations across Africa, which cost just $1 a dose. It has worked. Vaccinations are perhaps the greatest achievement of humanity: using this scientific tool, we have literally eradicated Smallpox – a disease that caused hundreds of millions of people to die in howling agony – from the human condition. It will never kill another person, ever. That's why the economist Jeffrey Sachs has called vaccines "Weapons of Mass Salvation".

So whenever somebody tells you science is "cold" or "soulless", and needs the "meaning" offered in religious texts, think of Marie. All the major religious texts say explicitly that disease is caused by demons and devils. Following this mentality left her babies to die. But using science instead – sticking to empirical observation of the world, and inferences from it based on reason – is saving millions of children, and giving them a chance at life once more. I can't think of anything less "cold" or "soulless" than that.

But today, some of the followers of faith-based thinking are waging a global war on vaccinations. At the turn of the twenty-first century, the WHO's vaccination programme was on the brink of sending polio to the graveyard of dead diseases. The disease leaves its victims permanently paralysed in various parts of their body: there is a brilliant account of what it is like in my colleague Patrick Cockburn's autobiographical book 'The Broken Boy.' But it had been chased down to a handful of remaining areas, which were being rapidly vaccinated. It was almost over, forever.

And then the local Mullahs heard about it. The Islamic clerical elite in northern Nigeria announced that God had revealed to them that the vaccine was "un-Islamic", part of an evil plot by the godless West to sterilise Muslim children. The local population, with no alternative sources of information, stopped sending their kids. Now polio is back with a vengeance, and we may never wipe it out. In a clash between reason and revelation, revelation won out – and as a direct result, millions of innocent people will be horribly paralysed and die.

But before we get smug and conclude this is a cultural gap between us and Those Damn Muslims, remember – in Britain, over the past five years, there has been a smaller but strikingly similar home-grown jihad against vaccinations. It has been waged by none other than the Daily Mail.

In 2000, the Daily Mail decided – in the absence of any reliable scientific evidence whatsoever – to give wildly undue prominence to the idea that the Measles, Mumps and Rubella (MMR) vaccine causes autism. Every reputable scientist in the country explained, patiently, that the sole scientist making these claims – Dr Andrew Wakefield – didn't have any reliable evidence at all to back him up. He had looked at only twelve autistic children whose parents all fervently blamed MMR – thus skewing his results irreparably. Instead, Britain's scientific community pointed to reams of studies showing conclusively that MMR is not to blame: a study of 1.8 million randomly-chosen children in Finland (as opposed to Wakefield's hand-picked 12) found that autism rates remained the same after the introduction of MMR.

But the Mail continued anyway, even after Wakefield was indicted before the General Medical Council, and it was – disgracefully – mimicked by other newspapers and by the BBC. Panicked parents assumed that, since it was on the news, there must some evidence for it, and in several areas vaccination rates have fallen by 30 percent. The result? Britain's chief scientist, Sir David King, warned last week that it is now probable fifty to one hundred kids will die of measles because of the disinformation campaign spearheaded by the Mail. It's rare a newspaper actually manages to kill people, but Sir David King believes they may pull it off.

Was the Mail's campaign based on faith-based thinking, like the campaign in Northern Nigeria? I think it can be shown that it was. Let's look at the figure within the newspaper who spearheaded the MMR campaign: Melanie Phillips. Despite having no scientific qualifications, and despite making the most elementary scientific howlers time and again in her articles, she feels free to announce that virtually all the world's scientists are wrong, on everything from global warming to MMR.

But why was she so certain the MMR campaign should be stopped? Phillips presented her argument as if she was simply siding with one scientist against another. But in reality, she disputes on religious grounds the very basis of vaccinations: evolution. She says that creationism should be taught in schools, and that evolution is "only a theory." So it's no wonder she is so hostile to (and ignorant of) vaccination science. Vaccines only work because we can observe evolution, live, as it happens. Take the flu virus. It is constantly changing – you can watch it under a microscope. That's why you need a booster shot every year: because the virus has evolved. That's why a vaccine against the 1918 flu virus would be radically different to a vaccine the 2007 flu virus: it has evolved. Yet when Professor Colin Blakemore, head of the Medical Research Council, pointed out this elementary scientific truth, she accused him of seizing any sneaky opportunity to "beat the drum for Darwin" and for claiming "there was no intelligent design in a virus, only the mindless force of natural selection."

Let me get this right: Phillips actually believes God personally tweaks the flu virus every year, just to keep it ahead of the vaccinators? What sort of sadist-deity does she follow? And why did newspapers and the BBC mimic her anti-scientific ravings? From this species of ignorance has flowed the serious risk of children dying, according to – remember – our chief scientist.

There have always been people who responded to life-saving scientific advances with peasant superstition and mutterings about the Almighty. For the sake of all that is good and un-Holy, it seems they still need to be resisted – from the deserts of Northern Nigeria to the hills of North London.