Puppies who are born to mothers who have been vaccinated against parvovirus and who have had an ample opportunity to nurse in the first day or two after birth will receive infection-fighting antibodies from their mothers. This “passive immune transfer” of maternally derived antibodies should protect them in the first few weeks after birth from an unlucky encounter with the parvovirus antigen.
These maternal antibodies gradually fade from the puppy’s system over the first few months of his life, and as they do so, they leave him vulnerable – unprotected from any viral antigens. That’s why we administer vaccinations to puppies starting at around 6 weeks of age; it’s an attempt to prompt his immune system to develop its own protective, virus-fighting antibodies as soon as his body is capable of doing so, and at the time his maternally derived antibodies ceased to protect him.
What happens if we administer his vaccinations when there are maternal antibodies still circulating in his system? Those antibodies will quickly recognize and neutralize the disease antigens in the vaccination – zap! The puppy’s immune system won’t be able to develop an adequate supply of its own antibodies from the very brief exposure it might have had to the antigens present in the vaccine because of what’s called “maternal antibody interference.”
The potential of this interference is why we vaccinate puppies several times over the first few months of their lives – because the maternal antibodies he may possess are capable of neutralizing the first few vaccinations he receives. And since the fading of the maternal antibodies happens at a variable time in each puppy – anywhere between 4 weeks and about 18 weeks of age – we vaccinate the pup several times, a few weeks apart. Repeat vaccinations are meant to reduce the window of opportunity between the degradation of the maternally derived antibodies and the development of his own vaccine-induced antibodies for viruses to infect him.
Keep Him At Home?
It used to be standard veterinary advice to keep puppies at home until they had received a vaccination after they were 18 to 20 weeks old (the “last of their puppy shots”). This advice was meant to prevent them from having any chance of coming into contact with the most common and dangerous viruses during a potential gap in antibody protection.
That’s a very safe recommendation as far as disease prevention goes – but, according to veterinary behavior experts, a downright disaster for the puppy’s social development. According to a position paper issued by the American Veterinary Society of Animal Behavior (AVSAB), protecting the puppy’s behavioral health by properly socializing her before she is “fully vaccinated” should be the higher priority. The position paper says:
“The primary and most important time for puppy socialization is the first three months of life. During this time puppies should be exposed to as many new people, animals, stimuli, and environments as can be achieved safely and without causing over-stimulation manifested as excessive fear, withdrawal or avoidance behavior. For this reason, the AVSAB believes that it should be the standard of care for puppies to receive such socialization before they are fully vaccinated.
“Behavioral problems are the greatest threat to the owner-dog bond. In fact, behavioral problems are the number one cause of relinquishment to shelters. Behavioral issues, not infectious diseases, are the number one cause of death for dogs under three years of age.
“While puppies’ immune systems are still developing during these early months, the combination of maternal immunity, primary vaccination, and appropriate care makes the risk of infection relatively small compared to the chance of death from a behavior problem.”
Today, we know how to help the puppies develop healthy behavioral skills and keep their exposure to disease antigens minimal. We do this by using carefully selected environments – such as private homes and well-managed, clean dog training centers – to expose vaccinated puppies (who may or may not have complete immunization, depending on their own immune development) to other humans, vaccinated dogs, and similarly well-managed puppies. We also vaccinate puppies at appropriate intervals until they are after the age of 20 weeks. This “safe socialization” should only minimally increase the puppy’s risk of viral infection, but will be highly protective of his healthy behavioral development.