Fevaxyn FeLV Dosage and administration Shake well before use. Administer the contents of one vial (1 ml) by subcutaneous injection using aseptic technique. Primary vaccination: A primary vaccination course consists of 2 doses, three to four weeks apart. The primary vaccination of kittens should start from the age of 9 weeks. The vaccination of female cats prior to mating is recommended to provide maternally derived antibody for the kittens. Boosting vaccination: A single annual booster vaccination is recommended for the maintenance of protection.