Mass inoculation of the American public against smallpox is a bad idea, according to two studies that say such a plan would cause substantial harm, including hundreds of unnecessary deaths, in most circumstances.

The two reports released yesterday by the New England Journal of Medicine suggest that a smallpox attack could be easily contained without mass inoculations.

``We cannot endorse a public vaccination campaign at this time, because the certainty of harm outweighs the small chance of a net benefit,'' said a study by the RAND Center for Domestic and International Health Security.

``Policy makers must balance the potential for saving lives against the likelihood of losing lives from complications of vaccination,'' it said.

In most scenarios, the expected number of deaths from vaccination would exceed the number of lives saved, it said.

Another report said the vaccine would result in three deaths per million people vaccinated, or about 800 fatalities if nearly the full population were immunized.

The report by Thomas Mack of the University of Southern California said the disease is not as infectious as most people think and said no more than 15,000 people need to be vaccinated.

``Smallpox is not as infectious as its reputation would suggest,'' he wrote.

``A terrorist introduction of smallpox could produce a short outbreak of cases and deaths, but the current vaccination policy will provide little protection and the cost in deaths from vaccine complications will outweigh any benefit,'' Mack wrote.

Release of the reports on the journal's Web site follows President Bush's announced plans to vaccinate soldiers, health-care workers and other emergency personnel who might respond to an attack. The government will make the vaccine available to anyone else who wants it beginning late next spring or early summer, though it will not encourage ordinary people to get the shots.

In a third report, Dr. Kent Sepkowitz of Memorial Sloan Kettering Cancer Center warned relatively little is known about the risk of hospital patients becoming ill or dying after becoming infected with vaccine virus from contact with recently vaccinated health care workers. Such infections may be fatal in up to 11 percent of cases, he said.

Hospital outbreaks ``seem to require relatively minor contact'' with the source of the infection, he said. Many patients are at risk for infection because of their compromised immune systems.

``Health care workers may carry virus on the clothes, on their hands . . .'' he wrote.

The journal also released a survey that found that most Americans are ready to be inoculated, but know little about the disease.

The survey of 1,006 Americans, conducted by the Harvard School of Public Health, found that 61 percent would be vaccinated if the vaccine were made available.

However, that support could be eroded sharply if people found out that their own doctors were not going to be immunized.

In a related matter, the federal government yesterday awarded Boston a $2.6 million grant to beef up its bioterrorism defenses.

It is the first such grant pocketed by any municipality since Sept. 11, officials said.

The Boston Public Health Commission plans to use much of the money to create a Public Health Training Institute, a sort of anti-bioterrorism boot camp for doctors and nurses. The commission also plans to expand its bioterrorism alert system. It tracks patient volume in the city's emergency rooms and sends up a red flag to public health officials in the event of a spike.

Thomas Caywood contributed to this report.