Combination MMRV vaccines second-dose cleared of risk of febrile seizures

A paper published today in the JAMA [Journal of the American Medical Association] Paediatrics reports that the use of the combination MMRV (measles-mumps-rubella-varicella) vaccine at 18 months was not associated with an increased risk of febrile seizures.

The combined MMRV vaccine was developed to reduce the number of shots required for young children.

A 2014 Canadian study found that the first dose of the MMRV vaccine has a slightly increased risk for seizures in children compared with vaccines administered separately for MMR and varicella (MMR+V).

The recent JAMA paper, titled “Evaluation of Combination Measles-Mumps-Rubella-Varicella Vaccine Introduction in Australia”, asked what the effect of the introduction of combination MMRV vaccine was at age 18 months as the second dose of measles-containing vaccine on vaccine coverage and risk of vaccine-associated febrile seizures in Australia.

The researchers analysed data for all Australian children aged 11 to 72 months, with 1471 Australian children aged 11 to 59 months included in the febrile seizure (FS) analysis, with a focus on those aged 11 to 23 months.

The conclusion was that vaccine coverage before and after the introduction of the MMRV vaccine showed improvement in uptake and timeliness for all four vaccine components.

“Despite the peak incidence of all-cause febrile seizures occurring at age 18 months and a known increased risk of febrile seizures following the first dose, in a self-controlled case series analysis including 1471 children, use of measles-mumps-rubella-varicella vaccine at 18 months was not associated with an increased risk of febrile seizures.

The Canadian study, published in The Canadian Medical Association Journal in June 2014, looked at data from 227,774 Alberta children between the ages of 12 to 23 months, who had received either the combined MMRV vaccine or the separate MMR+V vaccine between 2006 to 2010.

Its lead author, the University of Calgary’s Dr Shannon MacDonald, said that although febrile seizures are not typically associated with long-term health problems, they are still stressful for parents.

“Febrile seizures are typically self-limiting and rarely have long-term effects, but they can be extremely distressing for parents, may precipitate acute care visits and may undermine confidence in immunisation programs,” she said in a statement.

However, MacDonald noted that the absolute risk of febrile seizures from the vaccine is still very low, and the seizure risk from measles is much higher.

“We know from this study that the risks of febrile seizures from [measles] are tenfold higher than the risk from this vaccine,” she told CTV News.

“If you look at the absolute risk, we’re talking about three to four seizures for every 10,000 doses of the vaccine given, so the absolute risk is very small. But it’s something that parents should be aware of. Parents need to know what the benefits and risks of the vaccines are.”

Writing in The Conversation, Dr Kristine Macartney, lead author of the Australian study, said that “Combination vaccines not only mean fewer visits to the doctor or nurse for injections, they can have other benefits, as well as being safe.

Dr Macartney, MD, is Associate Professor in Discipline of Paediatrics and Child Health at the University of Sydney, as well as working in the National Centre for Immunisation Research and Surveillance, The Children’s Hospital at Westmead, Sydney.

“Our study highlights how much information is considered before making any change to the immunisation schedule to introduce combination vaccines, and importantly, how carefully changes to the schedule are monitored and evaluated,” she said.

“While combination vaccines might introduce extra antigens to a child’s immune system in one go, they are a tiny, tiny proportion of what children meet as they grow. Being vaccinated trains a child’s immune system to withstand some of the biggest and baddest germs they will encounter.”

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