December 29 will mark the third anniversary of the accident in Meribel, France but Schumacher's family and close associates have kept his condition largely secret.
The 47-year-old German is said to be recovering at his Swiss home, but his condition remains a mystery.
"Michael's health is not a public issue so we will not comment on it, just because we need to protect the privacy of Michael as much as possible," said his manager Sabine Kehm.
"We are aware that this is difficult to understand for some people, but we are in perfect agreement with Michael's attitude and we can only give our thanks for showing understanding."
The Schumacher family are setting up the "Keep Fighting" initiative to thank fans for their continued support of the seven-time Formula One world champion.
"We want to encourage others to never give up, the initiative is another sign of respect and thanks to Michael's fans," said Schumacher's wife Corinna.