VACCINATION USUALLY PRODUCES IMMUNITY AFTER ABOUT 14 DAYS, LASTING FOR ABOUT 6 MONTHS TO 1 YEAR. INJECTIONS ARE THEREFORE SCHEDULED ANNUALLY SO THAT THE PERIOD OF MAXIMUM IMMUNITY COINCIDES WITH THE USUAL PERIOD OF INFLUENZA INFECTION. IN THE UK AND USA, THEY ARE GENERALLY GIVEN BETWEEN SEPTEMBER AND EARLY NOVEMBER.
INFLUENZA VACCINES ARE GIVEN IN THE UK BY DEEP SUBCUTANEOUS INJECTION OR INTRAMUSCULAR INJECTION. THE PREFERRED SITE FOR INJECTION IS THE DELTOID MUSCLE IN ADULTS AND OLDER CHILDREN AND, IN INFANTS AND YOUNG CHILDREN, THE ANTEROLATERAL ASPECT OF THE THIGH. THE RECOMMENDED DOSE IS 0.5 ML FOR ADULTS AND CHILDREN AGED OVER 3 YEARS. IN CHILDREN AGED 6 MONTHS TO 3 YEARS, DOSES OF 0.25 OR 0.5 ML HAVE BEEN USED. CHILDREN SHOULD BE GIVEN A SECOND DOSE AT LEAST 4 WEEKS AFTER THE FIRST IF RECEIVING THE VACCINE FOR THE FIRST TIME. A LIVE INFLUENZA VACCINE IS GIVEN IN THE USA BY INTRANASAL ADMINISTRATION IN A DOSE OF 0.5 ML IN ADULTS AND CHILDREN AGED OVER 9 YEARS AND IN CHILDREN AGED 5 TO 8 YEARS WHO HAVE RECEIVED IT PREVIOUSLY. CHILDREN AGED 5 TO 8 YEARS WHO HAVE NOT PREVIOUSLY RECEIVED THE VACCINE ARE GIVEN A REPEAT DOSE AFTER ABOUT 60 DAYS.