FOR THE SUDDEN shortage of flu vaccine, there are many villains. Poor policies extend back over several administrations, and Republicans, Democrats, tort lawyers, drug manufacturers and regulators all bear some responsibility. You wouldn't know that, though, from listening to Sen. John F. Kerry and President Bush. Having missed an early opportunity to politicize the flu vaccine shortage in the third presidential debate, both nominees have now taken up the issue with a vengeance. In neither case does the rhetoric tell the whole story.

Mr. Kerry's attack on the president, in ads and stump speeches, essentially accuses the administration of ignoring long-standing warnings of a potential shortage: "Instead of fixing the problem, production of the vaccine was sent to a factory overseas -- the vaccines were contaminated." He has implied (rightly) that the shortage speaks ill of the nation's bioterrorism preparedness and (wrongly) that it says something significant about the health care system. Mr. Bush's response, by contrast, has been to call Mr. Kerry an "obstacle to flu vaccine production" because he voted against a bill that would protect vaccine manufacturers from lawsuits.

In fact, problems with the flu vaccination system began before Mr. Bush took office, and before Mr. Kerry's vote. In October 2000 the General Accounting Office (now the Government Accountability Office) produced a report questioning the nation's preparedness for a flu pandemic. In 2001, the agency documented the difficulties that manufacturers were beginning to have getting enough vaccine out on time, as well as the need to find ways to ensure access for high-risk people. The exodus of companies from vaccine manufacturing has long been predicted, for many reasons. Heavy regulation of the industry, the gathering threat of lawsuits -- the president is right; this is not a minor factor -- and uncertain, fluctuating markets that led to big annual losses pushed several companies out of the business and led others to look for short cuts. Chiron Corp., the company whose production failures caused this year's shortages, chose to refit an older factory rather than design a new one, a decision that may have led to this year's problems.

There are better, faster ways to make flu vaccine, using tissue culture instead of chicken eggs. But securing the private investment necessary to make that technology change, as well as the incentives needed to bring more companies back to the market, would require a level of government commitment and intervention that no administration has yet proffered and that Congress has not yet seriously considered. At the very least, the government would probably have to guarantee the purchase of a certain amount of vaccine every year and be more involved in its distribution. The Bush administration is spending more on flu preparation than its predecessors did, including on new technology research, but it has not yet offered such a guarantee. The next administration will have to make a quick decision about whether to do so. The candidates would do better to ponder that question than to point fingers at one another now.