inclusion criteria: * eligible participants were those who completed the two-dose primary series of icv for 6-15 months * voluntarily consented to participate in this trial * agreed to take effective contraceptive measures (women of childbearing potential) from signing the informed consent form to 12 months after booster vaccination.

inclusion criteria: * eligible participants were those who completed the two-dose primary series of icv for 6-15 months * voluntarily consented to participate in this trial * agreed to take effective contraceptive measures (women of childbearing potential) from signing the informed consent form to 12 months after booster vaccination.

inclusion criteria: eligible participants were those who completed the two-dose primary series of icv for 6-15 months voluntarily consented to participate in this trial agreed to take effective contraceptive measures (women of childbearing potential) from signing the informed consent form to 12 months after booster vaccination.

inclusion criteria: eligible participants were those who completed the two-dose primary series of icv for 6-15 months voluntarily consented to participate in this trial agreed to take effective contraceptive measures (women of childbearing potential) from signing the informed consent form to 12 months after booster vaccination.