A 1-year-old boy from Ingham County who was believed to have had measles in April actually was not infected with the virus — even though his initial test was positive, the Ingham County Health Department and the Michigan Department of Health and Human Services have announced.
“When we test for measles, the first test is very sensitive and can pick up both real infections and traces of the vaccine virus,” said Dr. Nike Shoyinka, Ingham County’s medical health officer, in a statement May 14. “Further testing showed the symptoms were likely from an unrelated illness and the positive test result was due to a recent vaccination, not a case of measles.”
The boy was exposed to a 1-year-old girl who had a confirmed case of measles earlier in April. He was undergoing monitoring by the health department when he developed general respiratory symptoms. That led health officials to test the boy for measles.
The test was positive, which triggered additional monitoring and public notification of his case. However, additional testing by a regional public health reference lab supported by the U.S. Centers for Disease Control and Prevention confirmed that the initial positive measles test result was caused by a recent vaccination with the measles, mumps, rubella (MMR) vaccine.
The MMR vaccine contains weakened live measles virus. This type of detection is not considered an infection and the child was not contagious, the health department said.
“With the availability of the additional testing, this case will no longer be counted as a confirmed measles infection by ICHD or MDHHS,” the statement said.
“This situation is a reminder of why timely vaccination is so important,” Shoyinka said. “The MMR vaccine is the best way to prevent measles and protect public health.”
In Michigan, there have been eight confimed measles cases this year, including a cluster of four cases in Montcalm County that constitute an outbreak.
Nationally, the CDC has confirmed 1,001 measles cases in 30 states as of May 8. Of them, about 68% have been among children and teenagers, and 96% have been among people who were either unvaccinated or whose vaccination status was unknown.
One dose of the MMR vaccine provides about 93% protection against the virus, and two doses offer about 97% coverage, the CDC says. It recommends the following for MMR vaccines:
Contact Kristen Shamus: kshamus@freepress.com. Subscribe to the Free Press.
This article originally appeared on Detroit Free Press: Ingham County: Vaccination triggered false positive measles test for Michigan baby
Reporting by Kristen Jordan Shamus, Detroit Free Press / Detroit Free Press
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