There are many myths about vaccinations floating around the Internet, says Dr. Simon Hambidge. One – that giving vaccinations too close together is unhealthy– has prompted some parents to request that their children receive vaccines on an alternate schedule, Hambidge told CNN in an e-mail.
Hambidge, an expert in pediatric vaccination with Kaiser Permanente’s Institute for Health Research Colorado, is lead author of a new study that examines the association between vaccine timing and seizures.
His team found that in the first year of life, there is no relationship between the recommended vaccine schedule and seizures.
But delaying the measles vaccine until after a child is 15 months old may raise his or her seizure risk. The study results were published Monday in the journal Pediatrics.
“A number of people have claimed that a young child’s immune system is not robust enough to be given multiple vaccines, and that it is safer to ‘spread out’ vaccination,” Hambidge said. “There is no scientific evidence for this, and there is evidence that it is safe and effective to follow the current recommended schedule.”
The study suggests that children who receive childhood vaccines in the first year of life do not have an associated risk of seizure. But seizure risk may increase in the second year of life with measles vaccines specifically.
The overall risk of seizures in vaccines that contain measles is “real but very low,” Hambidge said — it’s about 1 in 4,000 doses, according to previous research. It appears that the risk of seizures is about 2 in every 4,000 doses for children who receive the first MMR vaccine between 16 and 23 months of age.
Meanwhile, the study found that getting the MMRV vaccine, instead of the MMR and varicella vaccines separately, increases the risk of seizures twofold — regardless of whether the vaccine was given on time. The association with seizures was strongest for children who received the MMRV vaccine between 16 and 18 months of age.
The results support a 2010 study that found additional febrile seizure risk from using MMRV instead of MMR plus varicella separately. But the absolute risk remains small: For every 2,300 MMRV doses given in the second year of life, there is one additional febrile seizure in the seven to 10 days following vaccination.
Bottom line: Do what your doctor says and vaccinate against measles on time. Have a conversation about MMRV versus MMR if you have questions or concerns. The CDC recommends receiving the MMR and varicella injections separately.