Bredow was found in contempt of court last week and sent to jail for five days.
Before Bredow went to jail, she had primary custody.
Under state law, parents can chose whether to vaccinate their children but Bredow fell foul because she agreed to an immunisation schedule with her ex-husband, James Horne, in court proceedings in November 2016. Oakland County Jail gives a one-day credit to inmates who successfully serve five days so she was able to be released at midnight on October 9.
Bredow says she did this and that she and Horne had an agreement when their son was born to delay his vaccine schedule for three months. She told the Press that being in jail was "horrific" but "I still stand by my choices because I stand up for what I believe in".
Federal health officials say vaccinations are safe and can protect children and teenagers from more than a dozen potentially harmful diseases. "He's nearly 10 years old, so he understands more than the court would say I'm allowed to explain to him", Bredow said.
"It is our position that this case is not truly about vaccinations", Richardson said. In the intervening time, Bredow had physical custody, while Horne took charge of the boy on alternate weekends.
"She's devastated", Bredow's attorney, Steven Vitale, said.
"I understand you love your children. This was not leverage in any way", she said. There is no civil or criminal penalty for refusing to vaccinate your child in the US, and every state allows parents to opt out for medical reasons, while some states permit parents to decline vaccinations due to philosophical or religious reasons.
"Vaccines have been part of the fabric of our society for decades and are the most significant medical innovation of our time", the group said.