💉 Vet Guide: When to Vaccinate Foals | 2025 Guidelines for Immunity, Mare Status & Booster Timing 🐴

By Dr Duncan Houston, BVSc

One of the most common questions I get from breeders and first-time foal owners is: **“When should I start vaccinating my foal?”** The answer depends heavily on the **vaccination status of the mare**, the **colostrum transfer**, and **environmental risk**. 🧠🐎

In this 2025 guide, I’ll explain how foal vaccination timing works, what science tells us about early immunity, and how to build a vaccine plan that protects foals safely and effectively. ✅📆

🍼 The Role of the Mare in Foal Immunity

Foals are born with **no antibodies of their own**. Instead, they rely on the **first milk (colostrum)** from the mare to transfer passive immunity within the first 12–24 hours after birth. 🧬

Key Points:

• 👩‍⚕️ Only mares **vaccinated during pregnancy** pass protective antibodies in colostrum
• 🍼 Foals must nurse promptly and absorb colostrum efficiently
• 🧪 Foals can be tested within 12–24 hours for **IgG levels** to confirm passive transfer

This temporary immunity protects foals for the first several months—but it also creates a dilemma: **maternal antibodies can block vaccine response.** 🤔

📆 Traditional Vaccine Timing: Delayed Start

Historically, foals born to vaccinated mares were **not vaccinated until 4–6 months** of age, under the assumption that early maternal antibodies would neutralize the vaccine and make it ineffective. 🕒

Meanwhile, foals from unvaccinated mares were vaccinated **as early as 3 months**, due to lack of passive protection. 💉

🔬 The Kansas State Study: Challenging Old Assumptions

Veterinary researchers at Kansas State conducted a study to test whether foals vaccinated early could still mount an immune response—even with maternal antibodies present. 🧪

Study Design:

• 👶 Group A: Vaccinated starting at 3 months (3-dose series)
• 🧒 Group B: Vaccinated starting at 6 months
• 💉 Both groups received a **booster at 11 months**
• 🦠 Vaccines included: tetanus, encephalomyelitis, West Nile, and equine herpesvirus

Results:

• 📈 **All foals responded** to vaccination—regardless of age
• 🧬 Early vaccine series still produced **protective antibodies**
• ✅ Even foals born to vaccinated mares could respond by 3 months

This study shows that **early vaccination is not wasted**—and in high-risk situations, it may be beneficial. 🧠💡

🧠 When to Start Vaccines in 2025

Foals from Unvaccinated Mares:

• 📆 Begin vaccines at **3 months**
• 💉 3-dose core vaccine series + booster at 11 months

Foals from Vaccinated Mares:

• 🧪 Test IgG at 12–24 hours post-birth to confirm passive transfer
• 📆 Begin vaccines at **4–6 months** if low risk
• ⏱️ Begin at **3 months** if high exposure or foal has underlying risk
• 💉 3-dose core vaccine series + booster at 11 months

📋 Core Vaccines for Foals

All foals should receive a complete series of the following core vaccines in their first year: 💉

• 🧠 Tetanus
• 🦟 Encephalomyelitis (Eastern & Western)
• 🦟 West Nile Virus
• 🌬️ Equine Herpesvirus (EHV-1/4)
• 🌬️ Equine Influenza Virus (EIV)
• 🦠 Rabies (recommended by most states)

These vaccines protect against **fatal neurological, respiratory, and systemic diseases**—they’re non-negotiable. ✅

📲 Use Ask A Vet for Foal Vaccine Planning

The Ask A Vet app can help you time foal vaccines and monitor for passive transfer and immunity gaps:

• 🧪 Ask about IgG testing and colostrum protocols
• 📅 Track vaccine dates and booster intervals
• 💉 Upload vet records and antibody response results
• 🧠 Get guidance on when to start based on local disease risk

Start strong with the right vaccine plan. 🐴📲

✅ Foal Vaccine Timing Takeaways for 2025

• 🍼 Foals depend on colostrum for immunity at birth
• 📆 You can safely begin vaccines at 3 months—even with maternal antibodies
• 🧬 Study data shows early vaccines still produce a strong immune response
• 💉 3-dose series + booster at 11 months is ideal
• 📱 Use Ask A Vet to schedule, test, and track vaccinations

📲 Final Thoughts from Dr Duncan Houston

Foalhood vaccines lay the foundation for lifelong health—and now we know that **starting earlier may be both safe and effective**, especially in high-risk cases. Talk to your vet, test for IgG early, and work out a plan tailored to your foal’s needs and environment. 🧠💙

Download the Ask A Vet app to track foal vaccine schedules, monitor immune response, and ensure the safest start for your next generation in 2025. 🐎📱