Core vaccines for dogs are the shots every dog should receive regardless of lifestyle, location, or breed. The universally recognized core vaccines protect against four diseases: distemper, adenovirus (infectious hepatitis), parvovirus, and rabies. Depending on where you live, leptospirosis may also be considered core.
The Core Diseases and Why They Matter
The diseases targeted by core vaccines share two things in common: they’re widespread enough that every dog faces meaningful risk, and they’re severe or fatal with no cure once a dog is infected. Vaccination is the only reliable protection.
Distemper attacks a dog’s respiratory, digestive, and nervous systems. It spreads easily through airborne droplets and is often fatal, especially in puppies. Dogs that survive frequently have permanent neurological damage.
Parvovirus causes violent vomiting and bloody diarrhea, rapidly leading to dehydration and death without intensive veterinary care. It’s extraordinarily hardy in the environment, surviving on surfaces and in soil for months. Puppies under six months are most vulnerable, but unvaccinated dogs of any age can contract it.
Adenovirus (infectious canine hepatitis) targets the liver, kidneys, and blood vessels. The vaccine uses canine adenovirus type 2 (CAV-2), which cross-protects against the more dangerous type 1 strain that causes hepatitis. This is a historically severe and often fatal disease in dogs.
Rabies is always fatal once symptoms appear, in both dogs and humans. It’s the only dog vaccine required by law in most U.S. states, and vaccination schedules vary by state and product. Rabies vaccines must be administered by or under the supervision of a veterinarian.
Where Leptospirosis Fits In
Leptospirosis occupies a unique position. The American Animal Hospital Association (AAHA) classified the four-strain leptospirosis vaccine as core in its 2022 guidelines, recommending it for all dogs in the U.S. The World Small Animal Veterinary Association (WSAVA), which sets international standards, historically categorized it as non-core but updated its stance in 2024: in countries or regions where canine leptospirosis occurs and suitable vaccines are available, the vaccine should be considered core.
Leptospirosis is a bacterial infection spread through the urine of wildlife, often picked up from standing water or contaminated soil. Unlike the viral core diseases, it does have treatment options if caught early. But it can cause kidney and liver failure, and it’s one of the few dog diseases that spreads to humans. The vaccine requires two initial doses given two to four weeks apart, starting at 12 weeks of age, with annual boosters since immunity doesn’t last as long as it does for viral vaccines.
The DHPP Combination Vaccine
You’ll rarely see distemper, adenovirus, parvovirus, and parainfluenza given as four separate shots. They’re bundled into a single combination vaccine commonly called DHPP or DAPP (the abbreviations reflect slightly different formulations). Some versions are labeled as a “5-in-1” because they count the two types of adenovirus protection separately. Parainfluenza, a mild respiratory virus, is included in the combination even though it wouldn’t qualify as core on its own. Since it comes packaged with the others, most dogs receive it automatically.
Puppy Vaccination Schedule
Puppies are born with temporary immunity passed from their mother, but this maternal protection fades at an unpredictable rate. That’s why the puppy series requires multiple doses: some puppies lose maternal protection early, others hold onto it longer, and a vaccine given while maternal antibodies are still active won’t trigger a strong immune response.
The DHPP series starts no earlier than 6 weeks of age, with doses given every 2 to 4 weeks until the puppy is at least 16 weeks old. Most puppies end up getting three or four rounds. The 2024 WSAVA guidelines now recommend giving an additional dose at or shortly after 26 weeks (about 6 months) rather than waiting until 12 to 16 months. This change aims to catch the small number of puppies whose maternal antibodies were still interfering at the 16-week dose.
Rabies is typically given as a single dose, with timing determined by state law, usually around 12 to 16 weeks. A booster is required one year later.
Adult Booster Schedule
After the puppy series and the 6-month booster, the core viral vaccines (distemper, adenovirus, parvovirus) only need to be repeated every three years. This is a shift from older protocols that called for annual revaccination. Research has shown that immunity from these vaccines lasts at least three years, and many dogs maintain protection even longer.
Rabies follows a similar pattern: after the first-year booster, revaccination is recommended every three years using a product approved for that interval. Your state law may dictate the specific schedule.
Leptospirosis is the exception. Because it’s a bacterial vaccine and immunity wanes faster, it requires annual boosters to maintain protection.
Core vs. Non-Core Vaccines
Non-core vaccines are given based on a dog’s specific risk factors: where they live, whether they board at kennels, how much time they spend outdoors, and what diseases are common in the area. Examples include Bordetella (kennel cough), Lyme disease, and canine influenza. Your vet will recommend these based on your dog’s lifestyle.
Core vaccines, by contrast, aren’t optional in the same way. The diseases they prevent are either so dangerous, so widespread, or so relevant to public health (in the case of rabies) that the benefit applies to every dog.
Side Effects and Safety
Adverse reactions to vaccines are uncommon. A large-scale analysis found a rate of about 19 adverse events per 10,000 vaccinations. Younger dogs between 2 and 18 months had slightly higher rates, roughly 25 per 10,000, but that’s still well under 1%. French Bulldogs, Dachshunds, and Boston Terriers showed the highest breed-specific rates, though even in those breeds, reactions occurred in only about 45 to 55 out of every 10,000 vaccinations.
Most reactions are mild: soreness at the injection site, low energy, or a slight fever for a day or two. Serious allergic reactions are rare but can include facial swelling, vomiting, or difficulty breathing within minutes to hours of the shot.
Titer Testing as an Alternative
Titer testing is a blood test that measures your dog’s existing antibody levels against specific diseases, most commonly distemper and parvovirus. A positive titer indicates your dog still has protective immunity and may not need a booster. AAHA’s guidelines note that routine titer testing isn’t usually recommended as a replacement for boosters on the standard three-year schedule. It’s most useful for dogs that have had previous adverse reactions to vaccines, dogs with suspected vaccine-related autoimmune conditions, or situations where an owner has concerns about revaccination. Titer testing does not apply to rabies, where legal requirements override antibody results in most jurisdictions.