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The important points, first
- Core vaccines start at 6–8 weeks and are repeated every 2–4 weeks until at least 16 weeks of age.
- The last dose of the course should be given at 16 weeks or later. WSAVA then advises another dose from 26 weeks, or an antibody test.
- Puppy socialisation can start before the course is complete, under controlled conditions and only with healthy, vaccinated dogs.
- Which vaccines to add to the core ones depends on where and how your pet lives. Decide with your veterinarian.
Why several doses are needed
Maternal antibodies protect puppies and kittens, but they block vaccines. According to the 2024 WSAVA guidelines, in most animals they fall far enough between 8 and 12 weeks of age, with large differences between litters and even between littermates. This creates a period, called the window of susceptibility, when maternal antibodies no longer protect but can still block the vaccine. Without a blood test there is no way to know when it opens and closes for an individual animal.
Repeating doses every 2–4 weeks narrows that window as much as possible. For canine parvovirus, the AAHA guidelines note that maternal antibodies may last 13–15 weeks or even longer. Vaccination therefore continues beyond 16 weeks, and where the risk of parvovirus is high, 18–20 weeks is preferred.12
The basic schedule
For puppies, the core vaccines worldwide are those against distemper, adenovirus and parvovirus. WSAVA recommends starting at 6–8 weeks and repeating every 2–4 weeks, never less than 2 weeks apart, until at least 16 weeks. Some puppies still do not respond at that age, so WSAVA advises an antibody test from 20 weeks or another dose from 26 weeks. In dogs that responded well, boosters with core modified-live vaccines should not be given more often than every three years. Where these diseases occur, rabies and leptospirosis vaccines are also considered core.
For kittens, core vaccines protect against panleukopenia, herpesvirus and calicivirus. The schedule is similar: first dose at 6–8 weeks, then every 2–4 weeks until at least 16 weeks, and another dose from 26 weeks. How many injections are needed in total depends on the starting age and the interval chosen.12
Socialising without unnecessary risk
WSAVA considers early socialisation essential for healthy behavioural development in dogs, and explains that it can start before the vaccination course is complete. A US study followed 279 puppies, vaccinated at least once, that attended socialisation classes: none developed parvovirus, and their risk was no higher than that of vaccinated puppies that did not attend.
Until the course is complete, though, socialisation should happen under controlled conditions. The puppy should stay away from places outside the home that may be contaminated, and meet only healthy puppies and fully vaccinated adult dogs. Your veterinarian can point you to classes run with these rules.14
What to ask your veterinarian
Besides core vaccines, there are others recommended only for some animals, depending on where they live or travel and on their lifestyle. The AAHA guidelines recommend reassessing each dog’s vaccine needs at least once a year, partly because people travel more with their pets and diseases carried by insects and ticks are spreading.
Keep a record of the dates and products of every vaccination. According to AAHA, many parvovirus vaccine “failures” come from incomplete courses or from errors in storing and giving the vaccine. If you notice anything unusual after a vaccination, tell your veterinarian: WSAVA asks veterinarians to report all possible reactions.321
Sources and checks
Numbers in the text lead to the exact source. Commercial blogs and social posts are not used as evidence.
- 1Veterinary guideline
2024 guidelines for the vaccination of dogs and cats, compiled by the Vaccination Guidelines Group (VGG) of the WSAVA
World Small Animal Veterinary Association · J Small Anim Pract 2024, PMID 38568777 · Maternal antibodies and window of susceptibility, core vaccines, puppy and kitten schedule, dose from 26 weeks, early socialisation under controlled conditions, adverse event reporting.
Link checked on 16 Sept 2026 - 2Veterinary guideline
2022 AAHA Canine Vaccination Guidelines: Canine Parvovirus (CPV)
American Animal Hospital Association · Maternal antibodies for 13–15 weeks or longer, doses beyond 16 weeks (18–20 where risk is high), incomplete courses and errors among causes of “failure”.
Link checked on 16 Sept 2026 - 3Veterinary guideline
2022 AAHA Canine Vaccination Guidelines: Recommendations for Core and Noncore Canine Vaccines
American Animal Hospital Association · Core and non-core vaccines based on lifestyle and location; at least annual reassessment.
Link checked on 16 Sept 2026 - 4Peer-reviewed research article
Frequency of CPV infection in vaccinated puppies that attended puppy socialization classes
Journal of the American Animal Hospital Association (2013) · PubMed PMID 23325595 · 279 puppies vaccinated at least once attending socialisation classes: no parvovirus cases, risk no higher than in vaccinated puppies that did not attend.
Link checked on 16 Sept 2026
This guide describes the general recommendations of international guidelines. Your pet’s vaccination schedule should be set by your veterinarian, taking local requirements and risks into account.