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MMRV Vaccine Not Without Risk

Posted by Administrator on Sep 09 2014
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Monday, June 9, 2014 White Coat Black Art / Dr Brian Goldman / CBC News

A 2011 survey by the Public Health Agency of Canada found that one out of every three parents worry that vaccines aren't safe. That's despite reassurances from doctors. A study published today in the Canadian Medical Association Journal looks at the safety of a relatively new vaccine to prevent four childhood diseases.


The vaccine is called MMRV - which stands for measles, mumps, rubella and varicella - also known as chicken pox. The vaccine maker took the old MMR vaccine - and adds protection against chicken pox. This particular formulation - which has been around since 2007 - is currently used in nine out of ten provinces; BC joins the list this July. All three territories use the old type of vaccine. Alberta joined the list back in 2010, which makes that province an ideal site for a study.

Before MMRV, it was necessary for kids to receive separate shots for MMR and chicken pox. Combining both vaccines into one saves kids the pain of two needles when one will do.

Studies conducted prior to Health Canada approval of the vaccine showed that MMRV was about as safe as giving MMR and chicken pox vaccines separately - except for the observation that MMRV was more likely to cause fever in a vaccinated child. The researchers wanted to find out if that increased likelihood of fever posed a danger to kids who receive MMRV. The other reason for doing the study is to address that anxiety that at least a third of parents feel about vaccinating their kids.

Researchers from Alberta set out to find out if that extra fever posed a serious risk to vaccinated kids. So they looked at the risk that the child would have a fever in association with a seizure. Doctors call those febrile convulsions, which are defined as a brief seizure that occurs in association with fever in a child between the ages of six months and five years. The condition is not life threatening. Kids who have febrile seizures do not have a serious neurological or brain condition. They don't have epilepsy. They outgrow the tendency to have seizures in association with fever.

The researchers looked back at nearly a quarter of a million kids age one to two years who received either the new vaccine (MMRV) or the two older ones over a six-year period from 2006 to 2012. The old two-vaccine regime caused febrile convulsions at a rate of 2.2 per 10,000 doses of vaccine; the new single MMRV vaccine doubled the risk of febrile seizures to 5.8 per ten thousand doses of vaccine.

The results are statistically significant. However, the researchers point out that in absolute terms, they translate into very few additional seizures. In round terms, you'd have to give the MMRV vaccine to a just over twenty-eight hundred kids for one of them to have a seizure. Put in those terms, the absolute risk of a febrile seizure from MMRV vaccine is very low.

The authors of the study acknowledge that what some doctors or researchers find an acceptable risk could be quite disturbing to some parents. The researchers who did the study say it'll be important for doctors to tell patients about the risk as well the measurable benefit of causing less pain and suffering in kids by avoiding a second needle. They also suggest that doctors advise parents to monitor their kids for fever in the seven to ten days following MMRV vaccination and to treat the fever as needed.

Some may think that disclosing this risk - however small - will raise parental anxieties and perhaps lead them to think twice about vaccinating their kids. To me, doctors have no choice but to disclose the risk. Full disclosure of harm maintains the credibility of the public health position that vaccines do more good than harm. To not disclose the risk undermines that very credibility.

One way of allaying parental fears would be to allow them the choice of opting for the traditional two vaccinations (MMR + varicella). It`s something public health officials should consider..



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