Home > MMRV, Safety, Safety-General > Study links combination MMRV vaccine with double the risk for febrile seizures

Study links combination MMRV vaccine with double the risk for febrile seizures


The MMRV vaccine is a combination vaccine, which combines the MMR vaccine and the Varicella vaccine in a single dose. The MMR vaccine itself is a combination vaccine, providing protection from Measles, Mumps and Rubella. A recent study, published in the journal Pediatrics, shows that the risk for febrile seizures, in the 7-10 day period following receipt of the MMRV vaccine, is twice as big as compared to receiving separate MMR & Varicella vaccines in the same day, for children 12-23 months of age.

Measles-Mumps-Rubella-Varicella Combination Vaccine and the Risk of Febrile Seizures

Nicola P. Klein, Bruce Fireman, W. Katherine Yih, Edwin Lewis, Martin Kulldorff, Paula Ray, Roger Baxter, Simon Hambidge, James Nordin, Allison Naleway, Edward A. Belongia, Tracy Lieu, James Baggs, and Eric Weintraub for the Vaccine Safety Datalink 2010;126;e1-e8; originally published online Jun 29, 2010; Pediatrics DOI: 10.1542/peds.2010-0665

Study Summary – The researchers used 2000–2008 Vaccine Safety Datalink data to compare seizures and fever visits, restricted to emergency room or hospital visits,  among children aged 12 to 23 months, during the 42 days after receipt of the MMRV vaccine, or the separate MMR + varicella vaccines. The study population included 83, 107 children vaccinated with MMRV between January 2006 and October 2008 and 376, 354 vaccinated with MMR varicella between January 2000 and October 2008.  The secondary comparison groups consisted of 145, 302 children who received MMR vaccine alone and 107, 744 who received varicella vaccine alone from 2000 to 2008. The authors monitored weekly seizure visits and compared the rates between the vaccines.

Results – After vaccination with all measles-containing vaccines, seizure incidence peaked during days 7 to 10; the most prominent peak was recorded after MMRV vaccination. During days 7 to 10, unadjusted rates for seizures were 84.6 seizures per 1000 person-years after MMRV vaccination, 42.2 seizures per 1000 person-years after MMR + varicella vaccination, and 26.4 seizures per 1000 person-years after MMR vaccination alone. Unadjusted rates during days 7 to 10 were nearly 8 times higher for MMRV and 4 and 3.5 times higher for MMR  varicella and MMR vaccination alone, as compared to Varicella vaccine alone.

Conclusion – The study looked at over 459 000 children, 12-to-23 months of age, who were vaccinated with either the MMRV vaccine, or separate MMR & Varicella vaccines, and found the MMRV to be associated with increased fever and seizures 7-10 days following vaccination. When compared to separate MMR + Varicella vaccine received at the same time, the combination MMRV vaccine was associated with a two-fold increase in risk of having a febrile seizure in the 7-10 days following vaccination. The authors estimated this meant 1 additional case of febrile seizure for every 2,300 doses of MMRV vaccine given, as compared to separate MMR & Varicella vaccines received at the same time. There was no difference in seizure risk outside of the 7-10 day window. The study shows that both MMRV, and MMR+Varicella vaccines are associated with increased seizure risk in the 7-10 day window, as compared to Varicella vaccine alone, with the risk from MMRV being twice as high as the separate MMR+Varicella vaccinations. Here is what the authors of the study had to say:

Among 12- to 23-month-olds receiving their first dose of measles-containing vaccine, the risk of fever and seizure are elevated 7 to 10 days after vaccination. The use of MMRV vaccine instead of separate MMR  varicella vaccines approximately doubles the risk for fever and febrile seizures, resulting in 1 additional febrile seizure for every 2300 doses of MMRV vaccine administered instead of separate MMR and varicella vaccines.

Bottom Line:  Talk to your pediatrician about this; it appears the best route is to take the separate MMR+Varicella vaccines as opposed to the single MMRV shot. Febrile seizures are fairly common, with 1 in 25 children experiencing at least one seizure. While witnessing a child going through one is scary, they are generally harmless. According to the National Institute of Neurological Disorders and Stroke:

Although they can be frightening to parents, the vast majority of febrile seizures are harmless. During a seizure, there is a small chance that the child may be injured by falling or may choke from food or saliva in the mouth. Using proper first aid for seizures can help avoid these hazards (see section entitled “What should be done for a child having a febrile seizure?”).

There is no evidence that febrile seizures cause brain damage. Large studies have found that children with febrile seizures have normal school achievement and perform as well on intellectual tests as their siblings who don’t have seizures. Even in the rare instances of very prolonged seizures (more than 1 hour), most children recover completely.

Between 95 and 98 percent of children who have experienced febrile seizures do not go on to develop epilepsy. However, although the absolute risk remains very small, certain children who have febrile seizures face an increased risk of developing epilepsy. These children include those who have febrile seizures that are lengthy, that affect only part of the body, or that recur within 24 hours, and children with cerebral palsy, delayed development, or other neurological abnormalities. Among children who don’t have any of these risk factors, only one in 100 develops epilepsy after a febrile seizure.

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