A 15-month-old Lexington boy was sent to the hospital with serious injuries, after a one-car crash on Saturday on Interstate 95 in Walpole, according to the State Police. The boy, who was initially unresponsive, was revived and transported to Norwood Hospital, then Children’s Hospital in Boston, and his condition has been stabilized. A 5-year-old boy was taken to Children’s Hospital with potentially serious injuries. A 36-year-old man and a 33-year-old woman were also hospitalized, said State Police. All four are from Lexington. The crash occurred at about 12:40 p.m., after their 2007 Honda Accord left the roadway and struck a utility pole. The crash is under investigation.