Sooner the Better for Measles Vaccination
Children receiving measles-containing vaccines at 12-15 months of age have a lower increased risk of fever and seizures than those who receive them at 16-23 months of age, according to a new Kaiser Permanente study published in JAMA Pediatrics.
The Centers for Disease Control and Prevention recommends a two-dose series of measles-containing vaccines, with the first dose administered at 12-15 months and the second dose at 4-6 years of age. Most children receive their first dose of a measles-containing vaccine between the ages of 12 and 23 months; approximately 85 percent of children receive it by 19 months of age. The study found that receiving the first dose by 15 months provides a benefit to children.
Previous studies have shown that these vaccines administered to children 12-23 months of age are associated with an increased risk of febrile seizures one to two weeks following immunization. This is the period of time during which the vaccine virus replication is at its peak, potentially causing fever. The resulting fever may cause some children to experience a seizure.
While febrile seizures are the most common neurologic adverse events following immunization with measles-containing vaccines, senior author and co-director of the Kaiser Permanente Vaccine Study Center, Nicola Klein, MD, PhD, notes that the risk is small regardless of age: “Medically attended febrile seizures following immunization with measles-containing vaccines are not common events. Concerned parents should understand that the risk for febrile seizures after any measles-containing vaccine is low , less than one febrile seizure per 1,000 injections.”
Using data from the Vaccine Safety Datalink, a collaborative effort of the Centers for Disease Control and Prevention and nine managed care organizations, Kaiser Permanente researchers evaluated the potential modifying effect of age on the risk of fever and seizures following immunization with different combinations of vaccines: any measles-containing vaccines; and the measles, mumps, rubella and varicella vaccine compared with the measles, mumps and rubella vaccine administered with or without a separate varicella vaccine. Researchers evaluated the records of 840,348 children 12-23 months of age who had received a measles-containing vaccine between January 2001 and December 2011.
Following immunization with any measles-containing vaccine, the incidence of fever and seizures during days 7-10 was significantly greater than any other time during the 42-day post-immunization interval in all age groups. The patterns for the incidence of fever and seizures were different during the period of observation.
- The incidence of fever steadily declined from 12-13 to 19-23 months of age, while the incidence of seizures was highest among children 16-18 months of age.
- The relative risk of fever and seizures during the 7- to 10-day risk interval was significantly greater among children 16-23 months of age than among children 12-15 months of age.
- The risk of seizures attributable to the vaccine during the 7- to 10-day risk interval was significantly greater among children 16-23 months of age than among children 12-15 months of age.
Consistent with findings in previous studies, the incidence of fever and seizures during the 7-10 days following immunization with MMRV was significantly greater than that following immunization with MMR+V.
For more information, visit www.dor.kaiser.org .
About the Kaiser Permanente Vaccine Study Center
The Kaiser Permanente Vaccine Study Center (VCS) helps ensure that the nation’s vaccines are safe and effective by conducting research to advance scientific understanding of vaccines at all levels of development. In collaboration with DOR, the VSC coordinates clinical trials of new vaccines at Kaiser Permanente’s largest medical facilities in Northern California and other sites in Northwest, Hawaii and Colorado regions. VSC studies of new vaccines have led to licensing of vaccines to prevent diseases caused by Haemophilus influenza, pneumococcus, chickenpox, meningitis, and flu.
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