ASHINGTON, Feb. 20 — Amid growing fears that vaccines may harm babies' immune systems, an independent panel of experts said today that childhood shots did not increase the risk of juvenile diabetes, a disease associated with immune system dysfunction, or certain serious infections like meningitis.

But the evidence is inconclusive, the study said, on whether immunization increases the risk of asthma, another immune-related disorder.

The panel, an independent committee of the Institute of Medicine, has been examining the highly politicized issue of vaccine safety for the federal government. The new report, the third in a series of nine, said there was no reason for federal health officials to change the current immunization schedule, which calls for infants to receive as many as 15 shots in the first six months of life.

But the panel did call for further study, particularly research intended to show whether certain children had genetic predispositions for adverse reactions to vaccines. That pleased critics of vaccination, who have complained that their concerns are being ignored.

"For 20 years, we have been calling for studies of how and why some children are unable to handle the process of immunization like other children," said Barbara Loe Fisher, president of the National Vaccine Information Center, a group that represents parents who say vaccines have harmed their children.

The report, Ms. Fisher said, "is a major step forward."

In 1980, infants were vaccinated against just four diseases, diphtheria, tetanus, pertussis and polio. But today American children are vaccinated against a much broader variety of conditions, like chickenpox, hepatitis, measles and mumps. As the vaccination schedule has grown, so have parents' fears.

According to the new report, a survey found that 25 percent of parents agreed with the statement that administering too many vaccines was not good for babies and could weaken immune systems.

In London, parents are so concerned about reports that the vaccine for measles, mumps and rubella, or MMR, causes autism that one- fourth of eligible toddlers are not being vaccinated. The Institute of Medicine panel has already tackled that question, finding no link between the vaccine and the disorder.

In its report today, the panel did call for the Department of Health and Human Services to convene a group of experts to examine parents' perceptions and said doctors needed to learn how to discuss such fears with anxious mothers and fathers.

"People are just wondering if all of this is necessary," said Dr. Marie McCormick, chairwoman of the panel and a professor of maternal and child health at the Harvard School of Public Health. "We really need to have a much better, more comprehensive approach to understanding what people's concerns are."

Although it is true that infants receive more shots today than in the past, the study noted that children were now exposed to fewer antigens, the substances that vaccines use to initiate immune responses. A streamlined form of the pertussis vaccine has reduced the number of antigens, to fewer than 5 from 3,000, the report said. The smallpox vaccine, which contained 200 potential antigens, is no longer in use, and vaccines that have been added to the immunization schedule have relatively few antigens.

"When you look at the infant immune system," Dr. McCormick said, "it is quite competent and quite capable of handling larger antigen loads."

In examining a potential link to autoimmune disorders, the panel concentrated on Type 1 diabetes, an autoimmune form of the disease in which the body produces antibodies against its own insulin-secreting cells. A review of eight studies found that multiple vaccinations had no effect on the incidence of the disease.

A review of seven studies found that repeat vaccinations did not increase the risk of developing infections like colds, ear infections, meningitis and pneumonia.

A review of five studies on the potential link between vaccines and allergic diseases, including asthma, found some suggestion that certain shots increased the risk. But there were methodological weaknesses in those studies, the report said, and the panel urged further research.

Asked about asthma, Dr. McCormick said, "The evidence is not sufficient to say either yes or no." But, she added, asthma is a potential risk that has to be compared to "the very real risk of the disease for which children are being immunized."