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MMRV as second measles vaccine not linked to increased seizure risk
Administering measles-mumps-varicella-rubella vaccines to infants at 18 months — as the second measles-containing vaccine — is not associated with an increased risk of febrile seizures, according to a study published in JAMA Pediatrics.
“Disease outbreaks arising from measles importations demonstrated the need to improve two-dose coverage at all ages but especially in the young. A single dose of monovalent varicella vaccine had been scheduled under the National Immunization program at age 18 months since November 2005, but coverage by 2 years was only 86%, although it increased to 92% by 5 years,” Kristine Macartney, MD, from the National Center for Immunization Research and Surveillance in Sydney, Australia, and colleagues wrote.
The researchers note that although varicella-related morbidity and mortality has declined, models suggest that the burden of disease may shift to older age groups if single-dose coverage does not improve.
To assess the impact that scheduling measles-containing vaccination at 18 months has on safety and coverage, Macartney and colleagues conducted a national cohort study that explored vaccination coverage before and after the introduction of the MMRV vaccine in Australia. Children between the ages of 11 and 72 months were included in the analysis of vaccine coverage, and although a focus was placed on children between 11 and 23 months, those aged between 11 and 59 months were included in the febrile seizure analysis.
The median age at first febrile seizure in the 1,471 children included was 21 months (IQR, 14-31 months). Of the infants included in the study who were between 11 and 23 months and had at least one febrile seizure (n = 391), 52.9% were male. MMR was received, and followed by MMRV, in 71.1% of the children included, and 24.8% received only an MMR vaccine. Few received no vaccination at all (4.1%).
In the 5 to 12 days after MMRV was administered as a second measles-containing vaccine, no increased risk of febrile seizures was observed (RI, 1.08; 95% CI, 0.55-2.13), and a low increased risk of seizures was noted after the first dose of MMR vaccine (RI, 2.71; 95% CI, 1.71-4.29).
After this program was implemented, vaccination coverage of two-dose measles-containing vaccines was higher in those 36 months than those at 60 months, with on-time vaccination increasing 13.5% (from 58.9% to 72.4%). Although no changes were observed with the schedule change regarding varicella vaccination, a 4.0% increase was noted in single-dose varicella vaccine coverage with the use of MMRV.
“Within 2.5 years of implementing our compressed schedule at ages 12 and 18 months, we have demonstrated that more children were fully protected against measles at an earlier age,” Macartney and colleagues wrote. “In the United States, which has recently experienced a resurgence of measles, measles-containing vaccine dose two is recommended at age 4 to 6 years, and uptake of dose one at age 12 months could be more timely.” – by Katherine Bortz
Disclosure: The researchers report no relevant financial disclosures.
