AAP FactCheck - There is no evidence a child in the US contracted measles from an MMR vaccination, despite claims being made online.
Health authorities say the one-year-old developed symptoms after travelling through an airport at the same time as an infected person, and there is no evidence vaccination caused the infant to develop measles.
The false claim is spreading online after a surge of measles cases reported in more than half of US states.
New outbreaks of the highly infectious disease have also been recorded in Australia, New Zealand, Europe and Asia within the first few months of 2025.
"Michigan Baby Infected With Measles Got It From MMR Vaccine," one Facebook post1 reads.
The post links to an article published by The People's Voice, a website frequently checked 2by AAP FactCheck.
Michigan health authorities officially reported an outbreak 3of measles in the state in April 2025.
A one-year-old infant from Ingham County developed symptoms during an out-of-state trip, according to local news outlet WXYZ Detroit4.
The child had received her first dose of the measles, mumps and rubella (MMR) vaccine just one day before the family travelled through an airport where another individual was contagious5.
A spokesperson for Ingham County Health Department told AAP FactCheck there is no evidence the MMR vaccine contributed to the infant developing measles.
"The MMR vaccine did not cause the child's illness," she said.
"The child involved in this case had been appropriately vaccinated for her age prior to traveling out of state.
"However, because the exposure occurred shortly after vaccination, there was not sufficient time for full immunity to develop."
The health department was working with the Centers for Disease Control and Prevention (CDC) and Michigan health authorities to investigate the timing and location of exposure, she said.
Ingham County medical health officer Nike Shoyinka6 told the Detroit Free Press 7that the child was still susceptible to infection because the vaccine takes a few weeks to build an immune response.
"Usually, what we expect is that our body's immune system ... would have developed full immunity at about a two-week mark," Dr Shoyinka said.
"Even though this child was vaccinated, she was still relatively susceptible given the short period of time.
"However, I will say that this child's symptoms were very mild ... presumably because she had received at least one dose."
The MMR is a weakened live virus vaccine that builds immunity by causing a harmless infection in the vaccinated person, according to the Infectious Diseases Society of America. 8
In rare cases, the disease can occur after vaccination in people with compromised immune systems. Some children can also develop measles-like symptoms, but this is not measles.
A 2018 paper9 reported that vaccination with the MMR vaccine is safe, "but can very rarely be associated with clinically significant illness that is indistinguishable from wild-type measles".
AAP FactCheck has previously 10debunked false claims11 about the MMR vaccine, including the long-running myth that it causes autism12.
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