THURSDAY, Aug. 25, 2011 (HealthDay News) -- An exhaustive new report from experts at the Institute of Medicine finds that children's vaccines are typically safe, with bad reactions occurring only rarely and then not causing any lasting medical problems.
The IOM committee also agreed that there is no evidence supporting a connection between certain vaccines and the later onset of conditions such as autism or type 1 diabetes in kids.
The purported link between the measles-mumps-rubella (MMR) vaccine and autism, especially, has been hotly contested, both in the media and the courts in recent years. In 2010, the British researcher behind a 1998 study that was pivotal in suggesting such a link was accused of fraud and the journal that published it has since retracted the research.
In its review, the IOM committee examined more than 1,000 studies, looking for problems possibly related to vaccines, such as seizures, inflammation of the brain and fainting, as well as longer-term issues.
"We looked at eight different vaccines and a number of adverse effects, and what we found is that there is very little evidence that vaccines cause adverse events," said committee chair Dr. Ellen Wright Clayton, professor of pediatrics and law, and director of the Center for Biomedical Ethics and Society at Vanderbilt University.
"And most of the adverse events that there is evidence for tend to be time-limited," she said.
The report was requested by the U.S. Department of Health and Human Services to provide a scientific base for deciding on compensation for people claiming injury from any of the eight vaccines covered by the Vaccine Injury Compensation Program. The program was set up in 1988, and last February the U.S. Supreme Court upheld the 1986 law that created the program.
The report found evidence that in rare cases the MMR vaccine can lead to fever-triggered seizures, but these tend not to have long-term consequences, Clayton noted.
Also in rare cases, the MMR vaccine can cause brain inflammation in people with severe immune system deficiencies, she added.
In a very few children, the varicella (chickenpox) vaccine can cause brain swelling, pneumonia, hepatitis, meningitis or shingles. Most of these problems affect people with immune system deficiencies that increase susceptibility to the live viruses used in MMR and varicella vaccines, the report noted.
In addition, the MMR, varicella, influenza, hepatitis B, meningococcal and tetanus vaccines can cause a severe allergic reaction called anaphylaxis shortly after injection. In general, vaccine injections can result in fainting and inflammation of the shoulder, the committee said.
The evidence for other problems linked to vaccines is less clear, the report found.
The MMR vaccine might cause short-term joint pain in some women and children. Some people can have an allergic reaction after receiving the human papillomavirus (HPV) vaccine against cervical cancer, and some flu vaccines have resulted in a mild, temporary breathing problems.
Clayton noted that the "MMR vaccine and diphtheria-tetanus-acellular pertussis (DTaP) do not cause type 1 diabetes, and the MMR vaccine does not cause autism."
In addition, the flu shot does not cause Bell's palsy or worsen asthma, Clayton said.
But not everyone is convinced by the IOM's findings. Barbara Loe Fisher, co-founder and president of the National Vaccine Information Center, which has argued for more caution on the immunization of children, said the research is inadequate to determine whether vaccines are safe or not.
"You don't have enough studies that are methodologically sound," she said. "Whether the big increases in asthma and ADHD and other brain and immune system disorders among children is wholly or partly due to the fact that they are getting three times as many vaccines as children in the 1970s and early 1980s is a question that can only be answered by methodologically sound science. We are still left with the big question: Why are so many of our highly vaccinated children so sick today?"
Fisher disagrees with the committee's finding on the MMR and DTaP vaccines, and said she believes they can cause autism and type 1 diabetes. And she believes that parents should have the right not to have their children vaccinated.
"Vaccines should be available as a preventive health care option for all who voluntarily want to use them," she said. But people should not be required to vaccinate their children, she added.
But Clayton countered that it's important to remember what the vaccination of children and adults has achieved.
People who are critical of vaccines "don't remember the diseases that vaccines prevent such as polio, measles and chickenpox," Clayton said. And on the other hand, "a lot of the things that people worry about either don't happen, or there is not enough evidence to make a conclusion," she said.
Another infectious disease expert agreed. Dr. Marc Siegel, an associate professor of medicine at New York University, New York City, said that "current vaccines are safe and the benefits of protecting against the diseases way outweigh the risk of the vaccines."
Siegel also noted that vaccines not only protect an individual, but also protect the general population through what is called "herd immunity."
Research is needed to clarify how many vaccines should be given over what period of time and "if they are all necessary," Siegel said. "That's something that needs to be considered," he added.
For more information on vaccine safety, visit the U.S. Centers for Disease Control and Prevention.