Adverse Consequences of Vaccination (Part I)

Vaccination continues to be a safe, reliable and effective way of protecting animals against major infectious diseases.
Neverthless, the use of vaccines is not free risk.

Residual virulence and toxicity, allergic responses, disease in immunodeficient hosts, neurological complications and harmful effects on the fetus are the most significant risks associated with the use of vaccines.

Before using a vaccine, the veterinarian should consider both  the likelihood that an adverse event will happen, as well as the possible consequences or severity of this event.

Now in the next image you can see how we can classify the several consequences of vaccination, of course we will take one by one, and we won't extend to much on them, so let's see.

Normal Toxicity

The most common reactions to vaccines are local ones. For example, an immediate form of toxicity is the sting produced by some inactivating agents such as formaldehyde. This can present problems, not only to the animal being vaccinated but also, if the animal reacts in a violent way towards the vaccinator or Veterinarian, like biting or scratching (as most cats do),it can turn into a stressful situation for all parties involved in the consultation room.

More commonly, local swellings may develop at the reaction site. These may be firm or edematous and may be warm to the touch. They appear about one day after vaccination and can last for about a week. Unless an injection site abscess develops, these swellings leave little trace.

Vaccines containing gram-negative organisms (such as bordetella bronchiseptica), may be intrinsically toxic, owing to the presence of endotoxins that can cause cytokine release, leading to shock, fever, and leukopenia.

Even when the reaction is usually temporary, it may be enough to provoke abortion in pregnant females.

Inappropriate Responses

Vaccines may cause allergic reactions, for example: Type I hypersensitivity can occur in response not only to the immunizing antigen but also to other antigens found in vaccines, such as egg antigens from tissue culture cells.

Type I Hypersensitivity is an immediate response to an antigen and occurs within a few minutes or hours after exposure to an antigen. Reactions occurring more than 2 or 3 hours after administration of a vaccine are likely not type I hypersensitivity reactions.

Type III Hypersensitivity reactions are also potential hazards, they can cause intense local inflammation, or they may present generalized vascular disturbance such as purpura. They can occur in the eyes of dogs vaccinated against infectious canine hepatitis. Some rabies vaccines may induce a local complement-mediated vasculitis leading to ischemic dermatitis and local alopecia (this is more often seen in small dogs).

A common Type IV Hypersensitivity reaction is granuloma formation at the site of inoculation. This may be a response to depot adjuvants containing alum or oil. Vaccines containing a water-in-oil adjuvant produce larger and more persistent lesions at injection sites than vaccines containing alum and aluminum hydroxide. These lesions can be granulomas or sterile abscesses. If the skin is dirty at the injection site, these abscesses may become infected.

So of course we as Veterinarians have to be very careful with not only the handle we give the animals at the time of the vaccinations, but also we have to be very careful on what kind of vaccines shall we give the animals, keep them under observation, and of course the safety rule I will always apply, never put more than 2 vaccines in one visit, and never place them in the same site, specially on puppies and kittens.

So what are your thoughts on the vaccines? Has any of your patients ever had a vaccine reaction?
We will continue going through these vaccine consequences soon!




MVZ Carolina Pruneda