New city Health Department regulations are dealing another blow to parents who refuse to vaccinate their children. Now, in order to enroll in any city-run preschools or child-care centers, all 6- to 59-month-olds will be required to have a current flu vaccine by the start of the New Year. Like the elderly, kids are particularly at risk for serious complications from the virus. At least 7 children have already died from flu-related causes this year, and last year’s number was as high as 109.