The safety and immunogenicity of this experimental vaccine have been tested in multiple settings – including being given to hundreds of pregnant mares – with minimal adverse reactions similar to placebo controls.
. These experimental studies were conducted in cooperation and collaboration with the University of Kentucky.
Study One:
In the first vaccine trial, 25 healthy adult horses known to be negative for equine Rotavirus B were randomly divided into three groups. One group of 10 horses received our experimental vaccine. A second group of 10 received a similar vaccine containing a different Rotavirus B protein, and the third group of five control animals received a mock vaccine containing no Rotavirus B.
Each horse received two doses of their assigned vaccine in the neck muscle, three weeks apart. Following the first and second vaccinations, all animals were observed for any adverse reactions such as lethargy, inappetence, respiratory or gastrointestinal distress, neurologic impairment, and injection site inflammation. Results of this study showed no major or lasting adverse reactions, no fever or abnormal behavior in vaccinated horses. The serum samples were tested and evaluated for antibody, and those tests showed detectable titers that increased gradually over time after vaccination, not decreasing until after six weeks post-vaccination. Horses receiving the mock vaccine exhibited no detectable antibodies.
Study Two:
A second study then had 16 healthy, Rotavirus B-negative pregnant mares again randomly assigned into one of three vaccination groups: six mares received our experimental vaccine, four received the vaccine containing a different Rota B protein, and the remaining six control animals received a mock vaccine. All pregnant mares in each group were immunized three times in the neck muscle with 1mL of their assigned vaccine, at 8, 9, and 10 months of gestation with a 21-day interval between injections.
Mares were monitored for any vaccine reaction or changes in physiologic parameters. Serum was collected from all mares prior to vaccination, as well as multiple samples taken post-vaccination, at foaling, and postpartum, and colostrum samples were collected from each mare at the time of foaling.
The foals, at one day old, were challenged with the virus. Infected foals were then monitored for clinical signs and evaluated for fecal consistency, behavioral depression, and appetite. Fecal swabs from both mares and foals were collected daily; multiple serum samples were collected from foals; and milk samples from mares.
All vaccinated mares remained clinically normal, with no adverse reactions observed during the study, and all mares foaled normally. Serum from pregnant mares showed measurable antibody response that increased with each succeeding vaccination.
Five of the six foals born to the unvaccinated control mares developed moderate to severe diarrhea. In contrast, only 1/6 infected foals born to mares receiving the experimental vaccine developed a mild diarrhea that resolved without clinical intervention within 24 hours. Half of the foals receiving the other vaccine exhibited clinical diarrhea.
The foals receiving our experimental vaccine also exhibited a substantial decrease in virus shedding compared with the other two groups, and significantly higher antibody titers were observed in colostrum samples taken from their mothers.
Study Three:
These two small but successful tests led to a large field trial of the vaccine in 2024-2025, where over 800 pregnant mares were enrolled in a study where they received three doses of either a high-dose, low-dose, or mock (control) vaccine. Adverse reactions reported by all groups were low, with vaccinates not showing a significant difference from controls.
| Doses Administered | Vx Reactions |
Abortions* | Dead Foals^ |
|||
|---|---|---|---|---|---|---|
| Dose 1 | Dose 2 | Dose 3 | ||||
| Vaccine A | 323 | 315 | 274 | 3 | 6 | 13 |
| Vaccine B | 315 | 305 | 270 | 6 | 6 | 16 |
| Vaccine C | 317 | 312 | 278 | 2 | 6 | 14 |
| TOTALS | 955 | 932 | 822 | 11 | 18 | 43 |
*Abortions were typically evaluated by the Diagnostic Laboratory. No mare was sick, febrile, or inappetant at the time of abortion, leading us to believe the event was not due to a vaccine reaction. Some were found to have pre-existing subclinical placentitis; one was on a pasture with ergovaline levels documented at 2000pppb. Farm veterinarians did not associate vaccination with abortion.
^Dead Foals refers to death related to being born. Most were due to dystocia; other causes include neonatal maladjustment syndrome/meconium aspiration or physical malformations. None were due to diarrhea or issues we believe could be attributable to vaccination.