The three-dose vaccines should be given to boys and girls as follows: The first dose should ideally be given at age 11 or 12, but can be given to children as young as 9 or to young adults through age 26. The second dose is administered one or two months after the first. And the third dose is given six months after the first. Protection is not complete until all three doses are received. However, there is no maximum interval; if any dose is delayed, it should be given at the next opportunity. There is no need to restart the series.