Aug. 30, 2011—Vaccines are generally safe and cause few health problems, according to the findings of an independent committee of experts who sifted through more than 1,000 medical studies and articles about eight vaccines.

In particular, the committee said there’s simply no evidence that vaccines trigger autism and type 1 diabetes.

"With the start of the new school year, it's time to ensure that children are up-to-date on their immunizations, making this report's findings about the safety of these eight vaccines particularly timely," said committee chairwoman Ellen Wright Clayton, MD, professor of pediatrics and law and director of the Center for Biomedical Ethics and Society at Vanderbilt University. "The findings should be reassuring to parents that few health problems are clearly connected to immunizations, and these effects occur relatively rarely. And repeated study has made clear that some health problems are not caused by vaccines."

The committee, which was convened by the Institute of Medicine, reviewed the medical literature on these eight vaccines:

• Varicella zoster, for chickenpox.
• Influenza (not including the 2009 H1N1 vaccine).
• Hepatitis B.
• Human papillomavirus (HPV), which protects against cervical cancer and genital warts.
• Measles, mumps and rubella (MMR).
• Hepatitis A.
• Meningococcal.
• Certain tetanus-containing vaccines, including DTaP, the vaccine for diphtheria, tetanus and pertussis (whooping cough).

The varicella zoster vaccine contains live viruses and may cause side effects such as pneumonia, meningitis, brain swelling, hepatitis, shingles and chickenpox. These side effects occur in a minority of people who receive the vaccine.

The MMR vaccine also has live viruses. The committee found that it can cause fever-related seizures in infants and young children, although the seizures usually do not have any long-term consequences.

In addition, the committee found:

• No evidence to link the MMR vaccine and autism.
• No evidence to link the MMR or DTaP vaccines to type 1 diabetes.
• No evidence to link inactivated influenza vaccine to Bell’s palsy, a weakness of the facial nerve.
• No evidence to link inactivated influenza vaccine to a worsening of asthma or reactive airway disease in children.
• Evidence that six vaccines—MMR, varicella, influenza, hepatitis B, meningococcal and the tetanus-containing vaccines—can trigger anaphylaxis, a rare allergic reaction, after the injection. Anaphylaxis could be a problem after the HPV vaccine too, though evidence for that is not as strong.
• Evidence that some vaccines cause fainting or inflammation of the shoulder.

Many of the most serious problems happen in people who have weak immune systems, which increases their vulnerability to the live viruses in some vaccines, according to the committee.

The vaccines studied by the committee are ones that generated the most claims to the federal Vaccine Injury Compensation Program, set up to help people who may have been hurt by a vaccine.

Learn more about vaccination in the Vaccines health topic center.