Even as they are forced to wait like everyone else for swine flu vaccines in short supply, thousands of nurses and other front-line healthcare workers are fighting mandatory flu immunization policies being put in place by some U.S. hospitals.

The H1N1 pandemic, which has killed about 3,900 Americans so far, has stoked tensions over the best way to safeguard medical caregive

(Reuters) - rs and their patients from flu. Nurses unions have won some early battles against compulsory vaccination.

Most health experts and much of the public agree that medical personnel as a rule should be vaccinated. An infected nurse or technician can pass on a virus that could be deadly to a frail patient. But data from the U.S. Centers for Disease Control and Prevention show that only about 40 percent of U.S. healthcare workers ever get shots for seasonal influenza.

The question now dividing the medical community is whether it makes more sense to force health workers to get flu shots or to coax them into rolling up their sleeves voluntarily. Proponents of the mandatory route, adopted by a growing number of hospitals, say voluntary efforts largely have fallen short.

They just don't work, said Dr. Neil Fishman, president-elect of the Society for Healthcare Epidemiology of America. The bottom line is vaccination is the most effective way to prevent influenza.

He and other advocates of mandatory vaccination point to research they say shows steep declines in patient flu deaths and staff sick days when caregivers are immunized.

This is a harm that you can prevent, said Dr. Jonathan Perlin, chief medical officer for the Tennessee-based Hospital Corporation of America (HCA), one of the leading U.S. healthcare chains. It now requires 120,000 of its employees in 21 U.S. states to get seasonal flu shots.

Critics say mandating that healthcare workers get vaccines is misguided, ineffective and ultimately counterproductive.

There is no evidence that vaccination of healthcare workers in hospitals or outpatient settings has any impact whatsoever on patients, said Dr. Melanie Swift, head of occupational health for Vanderbilt University Medical Center in Tennessee. You've got to vaccinate the patients.

UNION CHALLENGES

Healthcare workers unions are challenging compulsory flu vaccine policies with some success.

The University of Iowa Hospitals and Clinics was ordered to halt its mandatory program this month after unions for nearly 5,000 employees there won two binding arbitration rulings that struck down the policy as a contract violation.

Union officials note that the Iowa City facility achieved an 84 percent vaccination rate among its staff last year under its voluntary program, a level considered exemplary.

Swift said this proves the success of educating healthcare workers, some of whom have the same misconceptions and fears about vaccines as the general public. Coercion, she argued, breeds distrust that undermines government safety assurances.

Last month, a New York judge sided with a nurses union and issued a court order against a statewide policy requiring flu shots for all medical workers. Days later, the state suspended its policy, saying the flu vaccine was too scarce to enforce.

Nurses unions also have filed lawsuits against HCA hospitals on behalf of its members in California and Nevada.

Critics of mandatory immunization say the danger posed in hospitals by influenza pales in comparison to many other bugs lurking in medical facilities.

The CDC reports 1.7 million people are stricken each year by all manner of hospital-acquired infections, such as pneumonia, and 99,000 of those die. The number of flu cases among them is unknown but believed to be very small.

When flu is carried unknowingly into hospitals, unvaccinated healthcare workers are hardly the only culprits.

Hospital are filled with visitors who come into close, regular contact with patients, and their vaccination status is almost never ascertained, Swift said.

Moreover, seasonal flu vaccines prove largely ineffective in some years against the actual strains that emerge. Thus, all other infection-control measures such as hand-washing and staying home when sick remain key to curbing flu's spread.

It is better to be vaccinated than not vaccinated, but it doesn't preclude the need for all these other controls, Swift said. You still have to behave the same way whether you're vaccinated or not.

(Editing by Maggie Fox and Will Dunham)