WHOOPING COUGH vaccine provides important protection to the vast majority of the children who receive it. But it harms some of them, a few severely and even fatally. The tragic cost of protecting the majority presents pressing questions of public equity and ethics that neither the country's public health authorities nor Congress have adequately resolved.

Lederle Laboratories, one of the two commercial manufacturers still producing the vaccine, has just announced that it is raising its price from $4.29 a dose to $11.40. The reason, Lederle explains, is that it has lost its liability insurance for this vaccine and will now have to insure itself. Of the new price, it says, $8 will in effect be an insurance premium against damage verdicts that are getting larger and more unpredictable. Three years ago the price was around 70 cents.

Even at the new price, parents will continue to have their children immunized. Whooping cough is an ugly disease, a notorious killer of infants and small children. Lederle is doing a public service by maintaining the supply of the vaccine. But it is possible to acknowledge that service and yet doubt that the liability risks fully justify that gigantic increase in the price.

One response may be to take the whole subject out of the courts and turn it over to a no-fault fund providing prompt and full compensation, with the government rather than the companies setting the premiums. But many parents of injured children vigorously oppose a no-fault system that would prevent them from suing the manufacturers. One parents' organization, Dissatisfied Parents Together, takes the position that liability litigation is the public's only weapon to force monopoly producers to work toward a better product. Since children are required by law to be immunized, these parents ask what incentive other than product liability will force the companies to develop safer vaccines.

If there were no hope of improving the vaccine, the rational solution would be the no-fault fund, promising automatic and generous aid to the families of injured children. But a lot of parents think that improvement is possible, and they demand that Congress leave open the route to the courthouse. There have been several recent attempts at legislation, but all have foundered on that basic difference. It appears that both houses of Congress are going to try again this year to reconcile those interests. Meanwhile, the price keeps uncontrollably rising.