If the current trend continues, 1977 could well be one of the worst years for measles outbreaks since nationwide inoculation against the disease began more than 10 years ago.

So far this year, there have been more than 4,500 cases of the childhood disease reported to the Central for Disease Control in Atlanta, double the number of cases reported by this time last year.

"If these trends continue we'll probably have a 75,000-case year," said Dr. Lyle Conrad, a CDC epidemiologist. Last year there were about 38,000 reported cases.

With the beginning of the mass vaccination program in the mid-1960s, the number of reported cases of the disease - which primarily affects children in the 4- to 8-year-old group - dropped from 204,000 cases in 1966 to a low of 22,000 in 1968.

The pattern of the disease has been roller coaster-like since then, climbing and dipping every few years, including a peak of 75,000 cases reported in 1971.

"I think people are letting the idea of getting immunized go by," said Dr. Robert H. Parrott, director of Children's Hospital. "I think that's the main problem."

According to CDC's Conrad, at no time have more than 75 per cent of children in the vulnerable age group been vaccinated, always leaving a large enough pool of unvaccinated children to keep the virus going.

One of the problems, said Dr. Donald Delaney, assistant director of Children's Hospital for patient care and education, is that parents do not take measles seriously enough.

"Someone who hasn't experienced measles think it's childhood disease of not very great import," Delaney said. ". . . Not until they see it and experience it in their children do they realize it's well worth every effort to get them vaccinated."

According to Conrad, there is about one death for every 1,000 reported cases of measles. Even without complications, the disease can cause a child discomfort and fever for up to two weeks.

In addition, the disease can lead to pneumonia and to encephalitis, which, with its high fever, can cause permanent brain damage and death.

The age at which children are most likely to be infected with the disease - the most contagious other than flu - varies depending upon whether they live in the city or country, Conrad said.

"In the city it's more a problem in the younger ages," he said, because children play together more at younger ages in urban settings." In the rural areas it's more a problem when kids come together in school" and spread the disease there, he said.

According to Conrad, the number of cases can only be reduced through a massive federal education effort.

Last year "we had only something like $4.9 million for the [entire] immunization program," Conrad said. "This year we have twice that. But it's probably going to take a constant effort of $10 million a year just for measles alone" to eradicate the disease, he said.

One of the difficulties in controlling the disease, Parrott said, is that a large number of children apparently were vaccinated at too early an age.

When the live vaccine - a serum containing minute amounts of live measles virus - was first developed, children were vaccinated at nine months.

The age was raised about three months ago the recommended age was raised once again, this time to 15 months.

The problem, said Parrott, is that researchers have discovered that the earlier a child is vaccinated, the more likely it is that he has some antibodies against the virus inherited from his mother. The mother would have the antibodies if she herself had ever had the disease.

If the child is vaccinated too soon after birth, and still has some of his mother's antibodies, those antibodies can kill the live virus contained in the vaccine, rendering it useless. (In order to prove effective, the vaccine must give the child a very mild case of measles, which will cause the child's system to create its own antibodies.

According to Parrott, the outbreaks have been occurring among "those who were never immunized, those who received live vaccine that did not take, and those who were vaccinated between 1962 and 1968" when a vaccine containing dead virus was used.