Vaccines can cause certain side-effects, but serious ones appear very rare, and there's no link with autism and Type 1 diabetes, the U.S. Institute of Medicine says in the first comprehensive safety review in 17 years.
The report isn't aimed at nervous parents. And the side-effects it lists as proven are some that doctors long have known about, such as fever-caused seizures and occasional brain inflammation.
Instead, the review comes at the request of the U.S. government's Vaccine Injury Compensation Program, which as the name implies, pays damages to people who are injured by vaccines. Federal law requires this type of independent review as officials update side-effects on that list to be sure they agree with the latest science.
"Vaccines are important tools in preventing serious infectious disease across the lifespan, from infancy through adulthood. All health-care interventions, however, carry the possibility of risk and vaccines are no exception," said pediatrician and bioethicist Dr. Ellen Wright Clayton of Vanderbilt University in Nashville, Tenn., who chaired the institute panel.
Still, this week's report stresses that vaccines generally are safe, and it may help doctors address worries from a small but vocal anti-vaccine movement. Some vaccine-preventable diseases, including measles, are on the rise.
"I am hopeful that it will allay some people's concerns," Clayton said.
The review echoed numerous other scientific reports that dismiss an autism link.
But it found convincing evidence of 14 side-effects:
- Fever-triggered seizures, which seldom cause long-term consequences, from the measles-mumps-rubella, or MMR, vaccine.
- MMR also can cause a rare form of brain inflammation in some people with immune problems.
- The varicella vaccine against chickenpox sometimes triggers that viral infection, resulting in widespread chickenpox or a painful relative called shingles. It also occasionally can lead to pneumonia, hepatitis or meningitis.
- Six vaccines — MMR and the chickenpox, hepatitis B, meningococcal and tetanus-containing vaccines — can cause severe allergic reactions known as anaphylaxis.
Vaccines in general sometimes trigger fainting or a type of shoulder inflammation.
There's suggestive evidence but not proof of a few other side-effects, including anaphylaxis from the human papillomavirus, or HPV, vaccine and short-term joint pain in some women and children from the MMR vaccine.
On the other hand, the report cleared flu shots of blame for two long-suspected side effects: Bell's palsy and worsening of asthma.
That doesn't mean there aren't other side-effects — the review couldn't find enough evidence to decide about more than 100 other possibilities. Some vaccines are just too new to link to something really rare.
Another example: Flu shots have long come with a caution about rare, paralyzing Guillain-Barré syndrome, but Clayton said research hasn't settled if that's a coincidence since the disorder is more common during the winter.
The U.S. Health Resources and Services Administration, which runs the vaccine compensation program, is reviewing the report but said it's too early to predict if it will prompt changes to the injury list.