Vaccinating pregnant dogs is generally discouraged because injecting a weak disease into a pregnant dog presents big risks for the puppies in utero. In some very rare cases where the potential benefits outweigh the risks, such as in rescue, then vaccines should be administered.

Vaccines protect us and our pets from diseases and viruses, when your dog is given a vaccine they are injected with a weak, modified version of the virus/disease. The vaccination will trigger an immune response in your dog, meaning he will produce antibodies that can fight against the disease causing bacteria. Consequently, if exposed to these diseases or viruses, they will already be equipped with the necessary antibodies needed to destroy the bacteria and prevent him from getting extremely ill.

As a rule, you should never vaccinate your pregnant dog with a “live” or “active” vaccine as these are not considered safe at any stage of pregnancy. Although the strain of disease or virus used in a live vaccine is weak, it still has the potential to cause underlying complications in-utero and may trigger a spontaneous abortion. There may be exceptional circumstances where the risk of your dam contracting a disease or virus and passing it onto the litter is much greater and more dangerous than a vaccine itself.

Some vets suggest that you can still vaccinate your pregnant dog with “killed” or “inactive” vaccines; the bacteria in these have been killed using heat or chemicals and therefore does not trigger such a strong immune response. However, this is still not recommended as puppies in-utero are extremely fragile.

Giving a vaccine to a pregnant dog triggers an antibody surge which is transferred to her puppies. Subsequently, the puppies will receive a greater level of immunity than they otherwise would. Most would assume this to be a good thing. However, usually, when a pup is born, it has its mother’s immunity for certain diseases up until 8-12 weeks old, after which the immunity wears off (which is why puppies receive their first set of vaccines at this point). Therefore, puppies who were in-utero when their mother was vaccinated still have stronger immunity than usual by the time their 8-week vaccines roll around, negating the effectiveness of the vaccines thereafter and compromising their immune system.

Ultimately the decision of whether to vaccinate your dog is your decision.

The stress that pregnancy puts on her body will also compromise her ability to fight naturally occurring bacteria present in the environment such as parvovirus.

If you do decide to vaccinate your dam, ensure you discuss the risks at length with your vet and ensure that the right vaccine is administered under the correct conditions. If you are still hesitating, it may be worth seeking a second opinion to help you reach a level of comfort within your decision.

It is best practice to avoid vaccinating a nursing dog unless they are in a particularly high-risk environment.

Vaccines will also provide no benefits whatsoever to the puppies of a lactating dam. In their first 12-24 hours of life, whelps receive antibodies from their mother through the colostrum and milk, but after that, they are on their own! It would take at least a week for the mother to produce a complete immune response to the vaccine and by this time the puppies will no longer be able to absorb them from her milk.

At best, the vaccination will provide some immunity for the mother but will do nothing for her offspring. It is worth speaking to your vet, as well as doing your own research.

Always make an informed decision.