People will fear flu vaccine 'adverse events'-study

* Officials can fight vaccine fears with statistics

* Cases of disease expected regardless of jabs

* Vaccine "myths" damage vaccination efforts

WASHINGTON, Oct 30 (Reuters) - 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 on Friday they could fight back with statistics.

Vaccination against pandemic H1N1 is underway in the United States, Britain, Canada and China and will start in other countries soon. And many people will associate bad events with the vaccine, said Dr. 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 6 weeks of vaccination," they wrote.

For every 1 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 undertstanding 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'?"

Global health officials have set up various systems for monitoring such adverse events to make sure the vaccine is not causing any particular health problems.

But they know many people will blame miscarriages or other health disasters on the vaccine.

"Widespread beliefs that such false associations are true can and do disrupt immunization programs, often to the detriment of public health," Black's team noted.

"For example," they wrote, "when an association between the measles, mumps, and rubella (MMR) vaccine and risk of autism was made, it had a negative effect on public uptake of measles prevention programs in the UK and elsewhere, with a consequent rise in morbidity (sickness) and mortality due to measles."

Fears about polio vaccines have disrupted efforts to eradicate the paralyzing virus in Nigeria, they added.

People have special fears about Guillain Barre Syndrome (GBS). a rare neurological condition that was linked to a 1976 U.S. swine flu vaccination campaign. Although no case of GBS was ever linked to the vaccine, a belief that the vaccine was worse than the illness remains widespread.

At any given time in the United States, one or two cases of GBS will be seen among any 1 million people in a given month.

If 100 million people are vaccinated, during the six weeks following 200 or more cases of GBS will be seen, completely independent of vaccination they said.

Only if this number goes over 200 should health officials start to be alarmed, they said. (Editing by Todd Eastham)