Why puppies and kittens need vaccine boosters every few weeks

In most cases, vaccines are given to puppies and kittens every few weeks until they are 14-16 weeks of age.  This is because the puppy/kitten will have maternal antibodies (antibodies acquired from the mother's milk/placenta) for some time after being born.  We give vaccines every few weeks in order to "hit the window of opportunity".  That means, every time  we give a vaccine to a puppy or kitten, that vaccine may not be effective because the mother's antibodies are still in the puppy or kitten's body.  These antibodies will interfere with the vaccine.  As the puppy/kitten grows, the maternal antibodies diminish and at one point, are no longer present.  The vaccine that is given when there are few or no maternal antibodies present will stimulate the puppy or kitten's immune system to produce it's own antibodies for the viruses vaccinate against.  This is what we call "the window of opportunity".  Research has shown that if you give a puppy or kitten vaccines every 3-4 weeks until 14 weeks of age or older, you will "hit the window of opportunity" in 99% of puppies and kittens.  Very rarely will a puppy or kitten acquire one of the viruses vaccinated for during the weeks between vaccines. You could run antibody titers in a puppy or kitten every week to determine if there are any antibodies in a puppy or kitten.  If the titer was low, then you would vaccinate your puppy or kitten.  However, this process is time consuming and expensive, considering you would have to run it many times between 8 and 16 weeks of age.  Thus, if we vaccinate every 3-4 weeks, we will ultimately stimulate a puppy or kitten's immune system and it really is cheaper in the long run to do a series of vaccines every few weeks.

Puppy vaccines

Puppies are typically vaccinated against these viruses: Distemper, Adenovirus (hepatitis), Parvovirus, and Parainfluenza (these are all in one vaccine and typically referred to as "the distemper shot").  Depending on your veterinarian and area where you live, puppies may also be vaccinated against Coronovirus, Giardia, Leptospirosis, Lyme disease, and Bordetella.  Puppies should also be vaccinated against Rabies anytime after 14 weeks of age.

The typical schedule for a puppy's distemper shot is every 3 weeks until 14-16 weeks of age.  Different vaccine schedules are listed below:

6, 9, 12, and 15 weeks of age
8, 11 and 14 weeks of age
9, 12 and 15 weeks of age
10, 13, and 16 weeks of age
13 and 16 weeks of age

If you bought a puppy at 14 weeks of age or older, and that puppy had never received any vaccines, the puppy still needs a series of 2 distemper shots.  The younger the puppy (less that 7 weeks of age), the more shots he/she will receive.  The distemper shot is then boostered one year after the last vaccine in your puppies distemper series, and yearly thereafter.  Ask your veterinarian regarding your puppies vaccine series and when and what shots are due.

Kitten vaccines

Kittens are typically vaccinated against these viruses: Rhinotracheitis (herpes virus), Chlamydia Psittaci, Calicivirus, and Panleukopenia virus  (these are all in one vaccine and typically referred to as "the distemper shot").  (Note: the distemper vaccine is different from puppies).  Depending on your veterinarian, if your kitten is indoor/outdoor, and how many cats/kittens you have, kittens may also be vaccinated against Feline Leukemia Virus, Bordetella and Feline Infectious Peritonitis (FIP).  Your kitten should also be vaccinated against Rabies anytime after 14 weeks of age.

The typical schedule for a kitten's distemper shot is every 4 weeks until 14-16 weeks of age.  Different vaccine schedules are listed below:

6, 10, and 14 weeks of age
8, 12 and 16 weeks of age
9, 13 and 17 weeks of age
10 and 14 weeks of age
11 and 15 weeks of age
12 and 16 weeks of age
13 and 17 weeks of age

If you bought a kitten at 14 weeks of age or older, and that kitten had never received any vaccines, the kitten still needs a series of 2 distemper shots.  The younger the kitten (less that 7 weeks of age), the more shots he/she will receive.  The distemper shot is then boostered one year after the last vaccine in your kittens distemper series.  After that, your veterinarian will let you know if the distemper vaccine will be do yearly or every 3 years thereafter.

The Feline Leukemia vaccine is a series of two shots, 3-4 weeks apart for any age cat that HAS NOT had that vaccine before.  Also, your cat should be Feline Leukemia tested prior to starting that vaccine.  Once your cat receives the two shots, the vaccine need to be done yearly thereafter.

The FIP vaccine is a series of two shots, 3-4 weeks apart for any age cat that HAS NOT had that vaccine before.  Once your cat receives the two shots, the vaccine need to be done yearly thereafter.

Ask your veterinarian about your kitten's vaccine schedule and what vaccines your kitten should receive.