Public health officials expressed frustration today at being blocked on religious grounds from examining students at Principia College here, where three young people have died in a measles outbreak that has stricken more than 100 students.

The college, operated by and for Christian Scientists, has permitted 415 of the approximately 750 students and staff to be immunized since the first measles case was reported Jan. 11. But the school has not approved a request by Illinois health officials to send a physician on campus to check on the conditions of 37 students still confined to a special-care facility.

"We considered that a suggestion," Dean David Pfeifer said. "We are not sure how to handle it."

Pfeifer added that the deaths are "indeed a tragedy . . . far outside the norm of Christian Scientists' experience, and are wholly unprecedented in our institution's close-to-90-year history."

Chet June, a spokesman for the Illinois Department of Public Health, said "it's my personal opinion their religious beliefs are making this a tragic situation. It's a shame that otherwise normal 18-year-olds are dying from something that is preventable."

June said that the stricken students are getting "plenty of fluids, excellent food and lots of fresh fruit. A hundred years ago it would have been thought to be good care."

June said that the students also attend organized prayer sessions.

"There is a lot of praying, a lot of laying on of hands," he said, "but it's not like what [evangelist] Jimmy Swaggart does."

Pfeifer responded that he has "no desire to compare our way of handling illness with the medical profession's way."

Nola L. Kramer, director of the Jersey County Health Department, said "we need to respect" the decision not to seek treatment, but added that she would feel better if she knew the condition of the students still under care. Pfeifer said that they are being cared for by Christian Science nurses who are "very skilled in providing practical care, keeping them warm and comfortable."

Kramer said local health officials had been unaware of the serious conditions of any of the victims until their deaths were reported.

The campus, situated on a bluff above the Mississippi River about 40 miles north of St. Louis, is virtually closed to outsiders.

A reporter was given a tour today only after promising not to interview anyone. His tour guide, Joel Manker, a security officer who is a 1983 graduate in studio art, said that while security has been stepped up since the measles outbreak, it is always strict.

"This is the only Christian Science college in the world," said Manker, who, like all students and employes of the college, is a member of the faith. "We want a place where we are not treated like a minority, and that can't happen if people can roam around and challenge our religious principles."

Pfeifer said that he had denied reporters access to students because some "are getting a little tired of all the questions." He noted that this is exam week.

The entrance to the 3,000-acre property is guarded around the clock from a gatehouse with railroad-crossing-type gates.

Jersey County coroner Paul Schroeder announced today that an autopsy on the body of Scott Shadrick, 19, of Holliston, Mass., confirmed that his death Feb. 22 resulted from complications from measles. Shadrick's sister, Sue Presley, is hospitalized in nearby Alton with measles, which Pfeifer said she apparently contracted while visiting her brother a few days before his death.

William Truitt, headmaster at The Principia, a preschool-through-12th-grade Christian Science school across the river in Missouri, announced today that its 750 students, 300 of whom are boarders, will get an early spring break in hopes of avoiding a measles outbreak there.

Pruitt said that he had turned down offers by St. Louis County health officials to vaccinate his students "because we don't have any measles here."

When it was mentioned that one of the three victims was a 16-year-old student at his school, Pruitt said "that's true," but that the student had commuted from Principia College, where her mother is on staff.