There is a growing group of parents who refuse to vaccinate their children, citing the belief that vaccines increase the risk of autism, diabetes, asthma and other ailments.
But a new report punches a gaping hole in these arguments, concluding that adverse effects from vaccines are extremely rare and that when they do occur, it is almost always among people with compromised immune systems.
The report, released on Thursday by the Institute of Medicine of the National Academies, analyzed the results of more than 1,000 previously published scientific articles to determine the strength of the evidence that specific vaccines were linked to specific adverse effects. The researchers looked at 158 vaccine-adverse event pairs and found that in 135 of them, there was not enough evidence to accept or reject a relationship.
Only six vaccines -- those for MMR, varicella zoster, influenza, hepatitis B, meningitis and tetanus -- were found to be conclusively associated with anaphylaxis, a life-threatening allergic reaction.
This does not, however, mean that the complication is common: it is rare, and as a precaution, doctors commonly require patients to stay in the office for 20 minutes or so to ensure that any allergic reaction can be promptly treated.
Meanwhile, five pairs, including the MMR vaccine and autism and the inactivated influenza vaccine and asthma, were found to be conclusively unassociated.
Vaccines are tested for safety before they enter the market, and their performance is continually evaluated to identify any risks that might appear over time, the researchers wrote in a report brief posted on the Institute of Medicine Web site. Vaccines are not free from side effects, or 'adverse effects,' but most are very rare or very mild. And, they emphasized, Some adverse health problems following a vaccine may be due to coincidence.
As more and more parents have shunned vaccinations, childhood diseases like measles and pertussis, or whooping cough, have been on the rise after many years of dormancy. Last year, for example, a pertussis epidemic in California sickened more than 900 children and killed at least 10.
Thursday's report could be a key weapon for public-health officials in persuading reluctant parents to vaccinate their children. The problem with individual resistance is that one parent's refusal to vaccinate their child does not just affect that child; it can potentially affect any other child who comes into contact with them, and it also siphons resources from doctors who have to spend time and money treating unvaccinated children for illnesses that could have been prevented.