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Monday 24th October 2016

Merck jab ups seizure risk

3rd March 2008

A four-in-one vaccination jab which protects children against measles, mumps, rubella and chicken pox has been associated with a higher incidence of seizures in toddlers in the United States.


ProQuad, manufactured by US-based Merck, doubled the risk of febrile seizures in children between 12 and 23 months old, although the risk was very low in the first place.

However, the risk is not doubled when children are given the three-in-one MMR jab and a separate varicella, or chicken pox, shot.

The vaccine has been plagued by distribution problems, meaning it is unlikely to be available in most US clinics until next year.

A study carried out by the US Centers for Disease Control and Prevention (CDC) found a cluster of cases of febrile seizure within a week to 10 days of the vaccine's administration, which is recommended at between 12 and 15 months.

Four out of every 10,000 children who got separate MMR and varicella shots on the same day had a febrile seizure seven to 10 days later.

But among the children receiving ProQuad, nine in 10,000 had febrile seizures seven to 10 days after vaccination.

Previously, CDC advisors had recommended ProQuad over separate shots because it limited the number of jabs a toddler needed to complete their immunisation programme.

But John Iksander, acting director of the CDC's Immunization Safety Office, said that view had now changed, with no preference between the two immunisation methods.

Once ProQuad is back in production, he said, the recommendation should be clear that people can continue to use the separate vaccines, or to opt to use the combined vaccine.

About one in 25 children has at least one febrile seizure, with most occurring in the first few hours of a child's fever.

According to the American Academy of Pediatrics, the child may look strange for a few moments, then stiffen, twitch, and roll his or her eyes.

Disturbed breathing, darkening of the skin and a short period of unresponsiveness are also signs to watch for.

Most febrile seizures are over in under a minute, although rare cases may last for up to 15 minutes. Febrile seizures are rare in children younger than age 6 months or older than 3 years.

The highest incidence of febrile seizures, from which most children recover with no lasting harm under medical supervision, is right at the time when the MMR and varicella vaccinations are recommended.

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