Characterisation of immune responses in healthy foals when a multivalent vaccine protocol was initiated at age 90 or 180 days.
Authors: Davis E G, Bello N M, Bryan A J, Hankins K, Wilkerson M
Journal: Equine veterinary journal
Summary
# Editorial Summary Early vaccination of foals remains controversial due to concerns about maternal antibody interference, yet disease risk exists before the conventional 6-month vaccination window. Davis et al. (2015) investigated whether a multivalent vaccine protocol could generate effective immune responses in foals vaccinated at 90 days compared to the standard 180-day protocol, using a randomised block design with 12 colostrum-fed foals receiving either early or delayed vaccination followed by a booster at 11 months. Both groups demonstrated comparable cellular immune activation—including antigen-specific CD4+ and CD8+ T-cell responses (interleukin-4, interferon-γ and granzyme B expression) to equine encephalomyelitis, West Nile virus, tetanus toxoid, influenza and herpesvirus antigens—measured at 30 days post-vaccination and again at 344 days of age. Memory responses were evident in both groups following the booster, with significant increases in antigen-specific immunoglobulin G, indicating that the immune system had retained recognition of the vaccine antigens. For practitioners managing foals in high-risk environments—such as those with infectious disease exposure or travelling to competitions—these findings suggest that initiating vaccination at 90 days generates immunologically comparable responses to conventional 180-day protocols, providing a practical option for earlier disease protection without sacrificing immune memory development.
Read the full abstract on PubMed
Practical Takeaways
- •Consider initiating multivalent vaccination protocols at 3 months (90 days) rather than waiting until 6 months in high-risk foals or situations where earlier immunity is needed; immune responses are comparable to conventional timing
- •Maternal antibodies do not prevent immune activation in young foals—do not assume early vaccination will be ineffective
- •Ensure booster vaccination at 11 months regardless of initial vaccination age, as this is critical for establishing robust memory immune responses and immunoglobulin G production
Key Findings
- •Foals vaccinated at 90 days showed comparable cellular immune responses (CD4+, CD8+, interleukin-4, interferon-γ, granzyme B) to those vaccinated at 180 days across six major antigens
- •Both groups demonstrated antigen-specific immune activation 30 days after initial vaccination and sustained responses at age 344 days
- •Both treatment and control groups showed significant increases in antigen-specific immunoglobulin G following booster vaccination at 11 months, indicating memory immune responses were established
- •Early vaccination at 3 months elicited comparable immune activation despite presence of maternal antibodies, providing evidence for earlier immunisation in high-risk situations