At what age should a puppy get its first shots?

Most veterinarians start the core vaccine series between 6 and 8 weeks of age, a window chosen because maternal antibodies absorbed through nursing typically begin declining enough by then for a vaccine to start generating the puppy's own immune response (American Animal Hospital Association, 2022). Starting earlier than 6 weeks is usually discouraged because residual maternal antibodies can neutralize the vaccine before it triggers protection, wasting the dose without adding risk-free benefit.

The AAHA Canine Vaccination Guidelines, developed with veterinary immunologists, recommend that the first core combination vaccine be given no later than 8 weeks in most pet dogs, with breeders and shelters sometimes starting slightly earlier in high-exposure environments (American Animal Hospital Association, 2022). A puppy adopted from a shelter or rescue at 8 weeks or older should already have documentation of at least one vaccine dose, which the new owner's veterinarian will use to plan the rest of the series rather than starting over.

Why do puppies need so many rounds of shots instead of just one?

The repeated-dose schedule exists because no one can predict exactly when an individual puppy's maternal antibody levels drop low enough to stop interfering with vaccination, so boosters are given every 3 to 4 weeks until the puppy reaches 14 to 16 weeks of age to make sure at least one dose lands after that window closes (Cornell University College of Veterinary Medicine, 2023). A puppy that only receives one or two doses may appear protected on paper but remain susceptible to parvovirus or distemper if maternal antibodies blocked those earlier shots.

This is why veterinarians are firm about finishing the entire series rather than stopping once a puppy seems old enough or big enough. AAHA guidelines specifically recommend a final core vaccine dose at 16 weeks or later, since this catches the small percentage of puppies whose maternal antibody interference persists longer than average (American Animal Hospital Association, 2022).

Which diseases does the core puppy vaccine actually protect against?

The standard combination vaccine given during the puppy series protects against four diseases: canine distemper virus, canine adenovirus (which causes infectious hepatitis), parainfluenza virus, and canine parvovirus, commonly abbreviated DAPP or DA2PP on vaccine records (American Veterinary Medical Association, n.d.). Parvovirus in particular remains a leading cause of death in unvaccinated puppies, with case fatality rates reported as high as 91% in untreated dogs versus far lower rates with aggressive veterinary treatment (Cornell University College of Veterinary Medicine, 2023).

Distemper spreads through respiratory secretions and can cause neurological damage that persists even in dogs that survive the initial infection, while canine adenovirus type 1 causes infectious canine hepatitis affecting the liver, kidneys, and eyes (Merck Veterinary Manual, 2023). Because these viruses circulate in the environment and in wildlife populations such as raccoons and foxes for distemper, unvaccinated puppies face exposure risk even in homes without other dogs.

Does my puppy need the rabies vaccine, and when?

Rabies vaccination is legally mandated in all 50 U.S. states for dogs, though the required age for the first dose varies by state law, generally falling between 12 and 16 weeks, with some states allowing up to 6 months (CDC, 2023). The background schedule referenced for this question notes a common range of 16 to 26 weeks, and veterinarians will confirm the exact requirement based on the state and sometimes county where the puppy lives, since local health departments enforce these rules differently.

Because rabies is fatal and transmissible to humans, the CDC tracks compliance closely and works with state agencies to set minimum vaccination ages and revaccination intervals, typically one year after the initial dose followed by boosters every one to three years depending on the vaccine product and state law (CDC, 2023).

Does my puppy need the bordetella or kennel cough vaccine?

Bordetella bronchiseptica, a bacterial contributor to kennel cough, is considered a non-core or lifestyle vaccine, meaning it's recommended based on a puppy's expected exposure rather than given to every dog automatically (American Animal Hospital Association, 2022). Puppies headed to daycare, group training classes, boarding facilities, or dog parks are typically advised to receive it, since these settings involve close contact with many unfamiliar dogs where the bacteria spreads easily through respiratory droplets.

Many boarding and daycare facilities require proof of a bordetella vaccine administered within the past 6 to 12 months before accepting a dog, which is often the deciding factor for owners weighing whether their individual puppy needs it (AVMA, n.d.). Intranasal and oral formulations can provide faster onset of protection than injectable versions, something a veterinarian can advise on based on how soon the puppy will be in a group setting.

Should I worry about leptospirosis for my specific puppy?

Leptospirosis vaccination has moved from a regional afterthought to a more broadly recommended non-core vaccine as the bacteria has been documented across urban, suburban, and rural areas, spread through contact with infected wildlife urine in soil, puddles, and ponds (AVMA, n.d.). It's also zoonotic, meaning infected dogs can transmit it to the humans in their household, which factors into many veterinarians' recommendation to vaccinate even city-dwelling puppies that visit parks or walk near standing water.

Because leptospirosis vaccines only cover specific bacterial serovars and protection can wane, some veterinary schedules call for an initial dose followed by a booster 2 to 4 weeks later, then annual revaccination for dogs in higher-risk regions (Merck Veterinary Manual, 2023). Owners in areas with heavy rainfall, wildlife activity, or a history of local lepto cases should ask their veterinarian directly whether their puppy qualifies as higher risk.

What happens if I fall behind on the puppy vaccine schedule?

Missing a scheduled dose doesn't necessarily mean restarting the entire series, but a puppy that goes more than 6 months between doses may need to begin the core series again depending on the specific vaccine product and the veterinarian's assessment of remaining immunity (AAHA, 2022). Falling behind matters most during the 6-to-16-week window itself, since a gap here can leave a puppy unprotected during exactly the period when maternal antibody interference is unpredictable and exposure risk from other dogs is highest.

Veterinarians generally advise keeping puppies away from dog parks, pet stores, and other areas frequented by unknown dogs until the full core series is finished, precisely because a partially vaccinated puppy can look protected while still being susceptible to parvovirus and distemper (Cornell University College of Veterinary Medicine, 2023). If a schedule has lapsed by weeks rather than months, most veterinarians simply resume the series rather than restart it from the beginning.

Do adult dogs still need vaccines after the puppy series is done?

Yes — most core vaccines require a booster roughly one year after the puppy series finishes, followed by revaccination every 1 to 3 years depending on the specific vaccine and the dog's ongoing risk factors, a schedule AAHA guidelines outline in detail for maintaining protection into adulthood (American Animal Hospital Association, 2022). Titer testing, which measures circulating antibody levels in blood, is an option some owners discuss with their veterinarian as an alternative to automatic revaccination for certain core vaccines, though rabies boosters remain governed by state law regardless of titer results (AAHA, 2022).

Non-core vaccines like bordetella and leptospirosis typically need more frequent boosters, often every 6 to 12 months, since immunity from these tends to be shorter-lived than immunity from the core combination vaccine (Merck Veterinary Manual, 2023). A dog's lifestyle — boarding frequency, travel, exposure to wildlife-heavy areas — should be revisited with a veterinarian at each annual visit rather than assumed to stay the same year to year.