By PHILIP M. BOFFEY

s public health officials debate whether to offer smallpox vaccine to every American who wants it, they would do well to recall what happened a quarter-century ago when a mass vaccination campaign ended in disaster. That experience — in the ill-fated swine flu immunizations of 1976 — does not mean that health officials should shrink from offering smallpox vaccinations today. But it does suggest there are lessons to be learned on how best to do it.

In 1976, concern was ignited by an outbreak of illness at Fort Dix, N.J., that included both a normal strain of influenza and a strain that seemed related to the swine flu of 1918 that killed anywhere from 20 million to 100 million people around the world. Although the swine strain at Fort Dix mysteriously disappeared after infecting some 500 soldiers, no one could say whether it would re-emerge or how lethal it might be if it did.

Some experts who had nervously been awaiting the return of a killer flu could hardly wait to spring into action to stop it. Brushing aside all qualms, health officials at the Centers for Disease Control in Atlanta and officials in Washington pushed through a presidential decision to vaccinate every man, woman and child in the country — more than 200 million Americans in all. Brief thought was given to simply making and stockpiling the vaccine so that it would be available should the swine flu reappear. But that was rejected on the theory that influenza moves too fast for a vaccination campaign to keep up with it.

Unfortunately, pretty much everything that could go wrong did go wrong. Manufacturing the vaccine took far longer than expected. The vaccine didn't work well in children. Bitter arguments over who should accept liability for side effects almost derailed the effort until the government assumed responsibility. And the states differed greatly in their enthusiasm and competence, resulting in extensive vaccination in some areas and very little in others.

Meanwhile, three coincidental deaths among elderly vaccinees at a Pittsburgh clinic forced a suspension in 10 states. Then, in the blow that killed the campaign for good, a rare side effect — a paralytic disease known as Guillain-Barre syndrome — appeared unexpectedly. This was a devastating shock to health officials who had considered influenza vaccines extremely safe. In all, some 532 people contracted Guillain-Barre after being vaccinated, and 32 of them died.

Many of these cases would have occurred anyway, but the vaccine itself was blamed for causing roughly 1 case of Guillain-Barre for every 100,000 people vaccinated. That seems like a small risk, but when the swine flu failed to reappear and the media zoomed in to record every disastrous side effect, the damage looked very big indeed. The campaign was halted after reaching only 45 million people. It was widely condemned as a fiasco, a debacle, a ghastly mistake, a medical Vietnam.

Now, once again there is a threat that could be dire but may not materialize. Nobody knows if terrorists or rogue states have access to the smallpox virus or a means to deliver it. The smallpox vaccine is considered one of the most toxic, causing life-threatening complications in 15 of every million vaccinees, of whom one or two might die. Health officials worry that in the absence of a smallpox attack, the vaccine damage will look just as awful in a media spotlight as Guillain-Barre did in 1976.

Still, the very existence of a vaccinated population should lessen the likelihood of smallpox being used as a weapon. When swine flu failed to appear, it was deemed evidence that the vaccination campaign was misguided. If no smallpox attack occurs, it could very well be due to a successful vaccination campaign.

Virtually all analyses of the 1976 failure suggest that the government must plan more carefully and prepare for the worst in such a huge undertaking. In some respects, the government is off to a better start this time. It separated the production of vaccine (already under way) from the decision over whether to stockpile it or administer it (yet to be made). It has adopted a phased approach, offering vaccine to health personnel first and only later, if at all, to the public. It has issued guidelines for states to follow in the event of attack. Officials are already pondering liability issues to iron out problems before the vaccinations start. And they are openly discussing the risks of the vaccine, ensuring that the downside of any campaign is recognized before it is launched. One big difference from 1976 is that the virus used in the smallpox vaccine has the potential to spread from those vaccinated to their close contacts, possibly endangering vulnerable people. That problem will have to be addressed with great care.

Most of the mistakes in the swine flu campaign were driven by the perceived urgency of acting quickly before a new flu strain could flash through the population. This time around, with no smallpox attack in immediate sight and vaccine stockpiles ready just in case, the deadlines for distribution are less tight. There is plenty of time for President Bush to get it right.