What will be the recommended interval between the first and second dose?
The FDA approved and the vaccine package inserts indicate that a second dose should be administered about one month after the initial dose. CDC recommends that the two doses of 2009 H1N1 vaccine be separated by 4 weeks. However, trials of the inactivated 2009 H1N1 vaccines have often used a 21 day interval. Administering the two doses of a 2009 H1N1 monovalent inactivated flu vaccine at least 21 days apart is safe and acceptable. Therefore, if the second dose of an inactivated 2009 H1N1 monovalent vaccine is separated from the first dose by at least 21 days, the second dose can be considered valid. If the interval separating the doses is less than 21 days, the second dose should be repeated 28 or more days after the invalid (second) dose (≥ 21 days is acceptable for this interval also).
