Canine influenza (dog flu) vaccine
Canine influenza is a relatively new disease in dogs -- the H3N8 strain emerged in racing greyhounds in the US in 2004, and the H3N2 strain (of avian origin) was first detected in the US in 2015. Unlike kennel cough, which is usually self-limiting, canine influenza can progress to pneumonia in 20-25% of infected dogs. The AAHA 2022 guidelines classify canine influenza vaccines as non-core but recommended for dogs in high-risk exposure settings.
H3N2 vs H3N8: understanding the two strains
H3N8 (original US strain)
- Emerged 2004 from equine influenza in Florida greyhounds
- Spread nationwide by 2008
- Lower current prevalence -- largely displaced by H3N2
- Vaccine available (single strain or bivalent)
- Not known to be present in UK
H3N2 (current dominant strain)
- Emerged 2015, of avian influenza origin (Korea)
- Major Chicago outbreak 2015; subsequent nationwide spread
- Can infect cats as well as dogs
- More contagious than H3N8; current major outbreak strain
- Bivalent vaccine (H3N2 + H3N8) recommended for coverage of both
Who needs the canine influenza vaccine?
Canine influenza spreads explosively in boarding environments. Major outbreaks have originated in Chicago, New York, Atlanta, and other high-density metro areas. Many kennels in outbreak-prone cities now require canine influenza vaccination.
Daycare facilities are the second most common origin point for canine flu outbreaks. If your daycare is in a city with a history of outbreaks (Chicago, New York, Atlanta, Florida metro areas), vaccination is prudent.
Competition events concentrating dogs from different regions are high-risk. Many AKC events and breed club shows require canine influenza vaccination. Check event rules.
Dog parks are potential exposure sites. AAHA 2022 lists canine influenza as recommended for 'dogs that frequent dog parks, dog shows, boarding facilities, or dog daycare'. Risk depends on local outbreak history.
Canine influenza is primarily an urban disease driven by high-density dog populations. Low-social-exposure rural dogs are at minimal risk and AAHA 2022 does not recommend the vaccine for low-risk dogs.
Vaccine schedule and cost
| Dose | Timing | Cost | Notes |
|---|---|---|---|
| Initial dose | 12--13 weeks, or any age in at-risk dogs | $25--60 | Bivalent H3N2+H3N8 recommended to cover both strains (Merck Nobivac Canine Flu Bivalent or Zoetis Vanguard CIV H3N2+H3N8). |
| Booster (2nd dose) | 2--4 weeks after initial | $25--60 | Primary series requires two doses 2-4 weeks apart for adequate protection. |
| Annual booster | Every 12 months | $25--60 | Annual boosters required. Influenza viruses evolve -- check if the vaccine covers current circulating strains. |
UK: canine influenza
Canine influenza is not established as an endemic disease in the UK. The H3N2 strain has been detected in imported dogs and in isolated small outbreaks, but it has not become a widely circulating virus. The BSAVA does not recommend routine canine influenza vaccination in the UK as of 2026. UK dog owners importing dogs from South Korea, China, or other regions where H3N2 is endemic should discuss vaccination with their vet. A UK canine influenza vaccine is not currently licensed for routine use.