What is the standard kitten vaccination series schedule and when should titers be used instead?

Question

Accepted Answer

The standard kitten core vaccine series begins at 6–8 weeks of age, with doses repeated every 2–4 weeks until 16 weeks of age or older, followed by a booster at 26 weeks (6 months) of age. Core vaccines are feline herpesvirus type 1 (FHV-1), feline calicivirus (FCV), feline panleukopenia virus (FPV), feline leukemia virus (FeLV) for kittens, and rabies.13 The number of doses in the primary series depends on the age at which vaccination begins. A kitten starting at 6–7 weeks of age requires four primary core vaccine doses; one starting at 8–9 weeks requires three doses.2 Intervals shorter than 2 weeks between doses interfere with successful immunization, particularly with attenuated live vaccines.1 The 6-month (26-week) booster for FHV-1, FCV, and FPV is recommended to close the window of susceptibility created by maternally derived antibodies (MDA). Up to one-third of kittens may fail to respond to a final core vaccine at 16 weeks and may retain blocking MDA levels at 20 weeks.1 The 26-week booster ensures that any kitten that failed to seroconvert during the primary series is protected before 12 months of age, rather than remaining unprotected until a traditional 12-month booster.23 Adopting this protocol may require up to five vaccine visits in the first 6 months of life when vaccination begins at 6–7 weeks.2 FeLV vaccination is core for all kittens and young cats under 1 year of age due to age-related susceptibility. The initial series consists of two doses 3–4 weeks apart, beginning as early as 8 weeks of age.1 FeLV revaccination is administered 12 months after the last dose in the kitten series, then annually for cats with regular exposure to FeLV-positive cats or cats of unknown status, or every 2–3 years (where product licensure allows) for adult cats with lower exposure risk.13 FeLV antigen status should be established by testing prior to vaccination.1 After the 26-week core booster, the next core (FHV-1/FCV/FPV) revaccination is not required for at least 3