As you may have heard about elsewhere, a new paper published today on the safety of childhood vaccines provides reassurance for parents and pediatricians that side effects from vaccination are rare and mostly transient. The paper, a meta-analysis appearing in Pediatrics, updates a 2011 Institute of Medicine report on childhood vaccine safety. It analyzed the results of 67 safety studies of vaccines used in the United States for children aged 6 and younger.

"There are no surprises here; vaccines are being shown over and over again to be quite safe," said Cornelia Dekker, MD, medical director of the vaccine program at Lucile Packard Children's Hospital Stanford, who chatted with me about the study earlier today. "The safety record for our U.S.-licensed vaccines is excellent. There are a few vaccines for which they document that there are indeed adverse events, but the frequency is quite rare, and in almost all cases they are very easy to manage and self-limited."

A Pediatrics commentary (.pdf) accompanying the new study puts the value of immunization in context:

Modeling of vaccine impact demonstrates that routine childhood immunizations in the 2009 US birth cohort would prevent ~42,000 deaths and 20 million cases of disease and save $13.5 billion in direct health care costs and $68.8 billion in societal costs.

The commentary goes on to contrast the risks of vaccines with the potential complications of vaccine-preventable diseases:

The adverse events identified by the authors were rare and in most cases would be expected to resolve completely after the adverse event. This contrasts starkly with the natural infections that vaccines are designed to prevent, which may reduce the quality of life through permanent morbidities, such as blindness, deafness, developmental delay, epilepsy, or paralysis and may also result in death.

The study found evidence against suspected links between vaccines and several acute and chronic diseases. For instance, the researchers found high-quality evidence that several different vaccines are not linked to childhood leukemia and that the measles, mumps and rubella (MMR) vaccine is not linked to autism. The DTaP vaccine is not linked to diabetes mellitus, and the Hepatitis B vaccine is not connected to multiple sclerosis, according to moderate-quality evidence.

The evidence does connect a few vaccines to side effects. For instance, the MMR, pneumococcal conjugate 13 and influenza vaccines are linked to small risks of febrile seizures, with the risk of such seizures increasing slightly if the PCV-13 and flu vaccines are given together.

"A febrile seizure can be quite alarming, but fortunately it does not have long-lasting consequences for child," Dekker said, noting that the risk of such seizures from vaccines is around a dozen per 100,000 doses of vaccine administered.

The rotavirus vaccine is linked to risk of intussusception, an intestinal problem that can also occur with rotavirus infection itself. But the benefits of rotavirus vaccination "clearly outweigh the small additional risk," Dekker said.

The study confirmed earlier research showing that some vaccines, including MMR and varicella, cause problems for immunocompromised children, such as kids who have HIV or who have received organ transplants. Since they can't safely receive vaccines, this group of children relies on the herd immunity of their community to protect them.

"It's not as if the parents of immunocompromised kids have a choice about whether to vaccinate," Dekker told me. "They have to depend on others to keep immunization levels high, and that starts breaking down when more people hold back from having their healthy kids fully immunized."

Dekker hopes the new findings will encourage more parents to have their healthy kids fully vaccinated.

Previously: Measles is disappearing from the Western hemisphere, Measles are on the rise; now's the time to vaccinate, says infectious-disease expert and Tips for parents on back-to-school vaccinations

Photo by Gates Foundation