Rabies Virus Neutralizing Antibody Levels in Veterinary Medical Professionals: A Cross Sectional Study from Samples Collected at U.S. Veterinary Continuing Education Conferences

Rabies is a viral pathogen primarily spread by animal bites; the resultant infection is a nearly 100% fatal. The American Veterinary Medical Association recommends all veterinary team members should receive pre-exposure rabies vaccination. The World Health Organization recommends that Rabies Virus Neutralizing Antibody (RVNA) levels should stay at or above 0.5 IU/mL. The goal of this study was to leverage an existing data set to look at trends of rabies vaccine seropositivity in vaccinated veterinarians and begin to investigate duration of adequate titer.
This was a cross sectional study using data which the Kansas State University (KSU) Rabies Laboratory generated by recruiting participants at veterinary continuing education conferences between 2018-2020. Of the 1788 participants this study, the majority (90%) of participants had RVNA titers which fell into the adequate range (>/= 0.5 IU/mL). The odds of women having inadequate RVNA was 56% lower (OR 0.44, 95% CI 0.31-0.63) than for men having inadequate RVNA. The odds of inadequate RVNA titers among participants from rabies endemic regions was 20% lower (OR 0.80, 95% CI 0.58–1.09) than for participants from non-endemic regions.
When exploring the duration of seropositivity, this study found that the odds of a participant having an adequate vaccine titer was 3% lower (95% CI, 2%-5% lower) for each year since last reported vaccination. The odds of a participant having an adequate RVNA titer decreased by 4% (95% CI, 1%-6%) for every one-year increase in participants age at time of vaccination.
This study is reassuring. It demonstrates that rabies vaccination results in long lasting seropositivity for most individuals. We also observed that women seem to be more likely to respond well to the vaccine and that vaccine antibody titers do wane over time. These data indicate that re-vaccination or titer testing should be done for those who continue to be at risk due to time since vaccination sex and age.