People will fear flu vaccine's 'adverse events' - study

Fear of adverse events such as miscarriages, rare neurological conditions and ordinary heart attacks will discourage some people from participating in mass vaccination efforts to fight swine flu, but public health experts said they could fight back with statistics.

Vaccination against pandemic H1N1 is under way in the US, Britain, Canada and China and will start in other countries soon. And many people will associate bad events with the vaccine, said Steven Black of Cincinnati Children's Hospital in Ohio and colleagues.

"Highly visible health conditions, such as Guillain-Barre syndrome, spontaneous abortion or even death will occur in coincident temporal association with novel influenza vaccination," they wrote in the Lancet medical journal.

So they calculated what might be expected anyway, even if there were no vaccination campaign.

"On the basis of the reviewed data, if a cohort of 10 million individuals was vaccinated in the UK, 21.5 cases of Guillain-Barre syndrome and 5.75 cases of sudden death would be expected to occur within six weeks of vaccination," they wrote.

For every one million pregnant women vaccinated, 397 will have a miscarriage, known medically as a spontaneous abortion, within a day - all unrelated to the vaccine, they said.

"If millions of people are vaccinated then just by chance we can expect bad things to happen to some of them, whether it's a diagnosis of autism or a miscarriage," commented David Spiegelhalter, a specialist in risk understanding at Britain's University of Cambridge.

"By being ready with the expected numbers of chance cases, perhaps we can avoid over-reaction to sad, but coincidental, events. And why don't we ever see a headline: 'Man wins lottery after flu jab'?"