As the swine flu vaccination programme gets underway, researchers have warned that the public needs help making decisions about risk, to avoid falling for health scares. Misinterpreting harmful events unrelated to the vaccine could threaten the vaccination programme and put people at risk of getting seriously ill.

The power of stories

Late last month, the media reported the sad death of Natalie Morton. She died shortly after receiving the HPV vaccine against cervical cancer, and there was speculation that she had suffered a severe reaction to the jab. However, a few days later it emerged that she'd died of a previously undiagnosed tumour in her chest.

It's only natural that personal, emotive stories should weigh heavily in our minds. However, the danger is that we fail to properly balance these stories against scientific research, which is less dramatic but gives us a better understanding of how safe vaccines are.

Researchers writing in The Lancet have pointed out that health scares will always be with us, simply because if you vaccinate enough people, something bad is coincidentally bound to happen to some of them. Harmful events may have nothing to do with the vaccine, but when one thing closely follows another, it's easy to jump to the conclusion that we're seeing cause and effect.

Sudden deaths in the UK

Unexplained deaths aren't common, but UK figures suggest that around 1 in 200,000 people between 16 and 64 die suddenly each year.

Assuming 10 million people were given the swine flu vaccine (around a sixth of the UK population), that would mean that simply by chance, one person would die suddenly within a week of their jab.

It's important that all drugs are closely monitored for side effects, but equally, not every harmful event that happens after having a vaccine will have been caused by the vaccine.

Pregnancy and the swine flu vaccine

Pregnant women are among the first to be offered the swine flu vaccine in the UK. It's reasonable to be cautious about medical treatment during pregnancy, but new research published by the American Journal of Obstetrics & Gynecology strongly supports pregnant women having the flu vaccine.

Figures from the United States show that, during the first four months of the swine flu outbreak, 32 in 100 pregnant women who got infected needed hospital treatment. That's four times the hospitalisation rate for healthy adults. Pregnant women accounted for 13 in 100 deaths from swine flu.

The researchers also looked back over all the previous research into flu vaccines. No study found any danger to mothers or their babies from having the inactivated flu vaccines that are currently used in the UK. One study looked at more than 2,000 pregnant women who had the jab for seasonal flu, and followed their children for seven years after birth.

If the swine flu vaccines are new, how can we be sure they're safe?

Two swine flu vaccines are approved in the UK, called Pandemrix and Celvapan. Although they've been developed to protect against the swine flu virus, in every other respect they're the same as seasonal flu jabs, which have been used for many years. According to the NHS, changing the strain of virus in a vaccine doesn't substantially affect its safety.

The nature of scientific research means that we can never say anything is completely risk-free. We can only say there's no evidence of risk. It's tempting to demand proof that a vaccine is totally safe, especially if you're pregnant. However, we know how dangerous it is to catch flu while pregnant, and there's also a risk of passing flu on to your baby. It's important to weigh these very real risks against any hypothetical risk from the vaccine.