There are 3 types of vaccines and depending
on the type generally determines whether boosters are
necessary or not. Vaccines are either modified live (MLV),
killed or recombinant. The first two are most common.
MLV are more like the original pathogen in
the way they elicit an immune reaction. In general, vaccines
that contain the living organisms will produce a stronger
and a longer-lasting immunity, but their virulence is
reduced to a safe level (attenuated). Once MLVs are
introduced into the body they elicit the expected immune
response, but die rapidly and rarely cause the disease. MLVs
can shed vaccinal virus into the environment which can be a
risk for unvaccinated animals or immunocompromised animals.
Examples of MLVs are Canine Distemper, Canine Parvovirus,
Canine Adenovirus and Canine Parainfluenza.
Killed or inactivated vaccines are safer
because unlike the MLVs they do not shed virus into the
environment nor can they cause the illness they are supposed
to be preventing. However, in order to maximize their
effectiveness, killed vaccines often have adjuvants in them.
Adjuvants stimulate an inflammatory response to increase
the immune response. Killed vaccines also may have remnant
chemicals which were used to kill the bug so one can see
reactions from the chemicals or the adjuvant, but one can
not get the infection from a killed vaccine. Killed
vaccines don’t tend to stimulate the immune system as much
as MLV so booster doses for killed vaccines are often
required. Examples of killed vaccines are Rabies, Canine
Influenza, Canine Coronavirus, Lyme, Bordatella,
Leptospirosis.
In a recombinant vaccine, the “bug” has had
its genetic material artificially modified. This
modification usually involves deletion of all or part of
some genetic material or the insertion of one or more genes
from another organism. USDA has classified three different
types of recombinant vaccines - subunit, gene-deleted and
vectored. Examples are Merial’s distemper, canine parvo,
corona and lyme vaccine.
When determining which vaccine, the type of
vaccine, when to start vaccination in a puppy and frequency
of vaccination (if boosters are required), one needs to look
at several factors and discuss them with your veterinarian:
(1)
Environmental exposures – where the dog lives (what bugs
are endemic like Lyme in deer infested areas of NE USA),
where the dog goes (shows all over the country vs
backyard pet that is generally always home);
(2) Breed
of dog – some breeds are either oversensitive to a type
of vaccine or its adjuvant and some breeds develop poor
immunity to a particular vaccine, likely genetic in
nature.
(3)
Amount of passive immunity the puppy receives (in utero
and from colostrum) – orphaned pups will likely need
vaccination sooner than pups that got colostrum.
(4) Laws
regarding vaccination (i.e. USA laws requiring rabies
vaccine).
(5)
Health of dog – immunocompromised or sick dogs – these
dogs are vaccinated differently or their vaccinations
are delayed.
Why do
some vaccinated pups get the illness from the vaccine that
was supposed to prevent it? There are several possible
reasons that can negatively impact on the effectiveness of
vaccines: (1) maternal antibody interference; (2) stress,
such as flying a dog immediately after vaccination; (3)
animal has poor immune system (3) parasites or other
concomitant illnesses; (4) poorly handled, stored or
administered vaccine; (4) vaccines give too close together
or given too far apart; (5) variant stains not covered in
the vaccine. (6) owners assumption that the vaccination
infers immediate immunity and takes the dog to a high risk
area. I’m sure there may be others.
Properly administered vaccination for humans
or dogs is not an absolute or sure thing. No vaccine
produces 100% protection all of the time. All dogs are not
the same, they have differently functioning immune systems
that respond differently to vaccines. Please do your own
research for your own dogs. Rely on evidence-based
information, like vaccine studies, studies regarding titer
testing. Your vet should be willing to help you locate this
type of information which will help in making the right
decisions for your dogs.
Information
present in the scientific literature suggests that parvo’s
CPV-2c (aka F-strain) is very similar genetically to CPV-2a
and CPV-2b; and, that vaccines developed prior to the
discovery of CPV-2c protect dogs from the CPV-2c challenge.
This new 2c strain seems to be more virulent with faster
onset of symptoms so any inkling of parvo, seek medical care
immediately for supportive care.
For more information about
vaccines please
contact me.
