Research Summary - 2
Evaluation of the safety of MLV IBR fraction of a 5-way intranasal vaccine on heifer pregnancy and newborn calf health
| Date/Time: |
9/12/2025
16:30
|
| Author: |
Jan Gawthrop |
| Clinic: |
CalfCare |
| City, State, ZIP: |
Arrington, TN 37014 |
Douglas Braun, DVM MBA
2
;
William Swafford, DVM
3
;
Troy McElveen, BS
1
;
1CalfCare 11937 N State Rd 13, N. Manchester, IN 46962
2Huvepharma 525 Westpark Dr. Peachtree City, GA 30269
3Swafford Veterinary Consulting 1178 Meadow Bridge Lane, Arrington, TN 37014
Introduction:
Vaccination is a cornerstone of Bovine Respiratory Disease control, but concerns persist regarding the potential risk of Infectious Bovine Rhinotracheitis (IBR) exposure to pregnant cattle, particularly from nursing calves shedding the virus from their nostrils after administration of an IBR modified live virus (MLV) vaccine. For breeding age females, administering a pre-breeding modified live (MLV) vaccine is utilized to mitigate IBR within the herd. Administering a 3-way intranasal Bovine Rhinotracheitis-Parainfluenza 3-Bovine Respiratory Syncytial Virus (MLV) vaccine to calves nursing pregnant females is common practice (i.e., branding time or pre-weaning vaccinations) to reduce BRD. There is concern that MLV-vaccinated nursing calves can shed the IBR virus from their nostrils post vaccination increasing the risk of IBR abortion in pregnant females in the herd. The objective of this study conducted on 2 commercial dairies was to evaluate the safety of the IBR fraction of a 5-way intranasal vaccine including IBR-PI3-BRSV MLV/attenuated live Pm-Mh administered to pregnant heifers as an exaggerated dose potential to cattle exposure from vaccinated, nursing calves during each trimester of pregnancy.
Materials and methods:
Experimental design in which pregnant heifers were directly inoculated intranasally with the test vaccine to mimic exposure via shedding from calves’ nostrils. The study evaluated safety for both pregnant females and newborn calves and monitored abortion rates and offspring health compared to unvaccinated pregnant heifers as controls. The study was conducted on commercial dairies involving 1,253 pregnant Holstein and Holstein-cross heifers pre-breeding vaccinated against IBR with one of two licensed parenteral MLV vaccines. Heifers in first, second or third trimester of pregnancy were randomly allocated to vaccinated or unvaccinated control groups receiving either a 5-way intranasal MLV vaccine (IBR-PI3-BRSV-Pm-Mh) or a sterile water placebo. First and second trimester heifers were reassessed at 84 days post-vaccination for effect on pregnancy. All heifers were followed to parturition and health status of calves born from all heifers were assessed daily until 28 days of age. For the analysis of the occurrence of abortion (primary outcome) each heifer was designated YES or NO. Since no abortions were IBR related, a single Clopper-Pearson 95% confidence interval was calculated.
Results:
Heifers by trimester that completed the study, controls and vaccinates respectively; first (200/207), second (209/210), third (201/210). There was a total of 28 abortions (16 controls and 12 vaccinated heifers). The abortion rate was 2.26%. None of the samples from aborted heifers or fetuses were positive for the presence of IBR virus. Heifers gave birth to 1188 live calves (583 from controls, 605 from vaccinates. Calves were monitored for 28 days. Pre-suckling blood samples from 98 calves (50 and 48 respectively from trimesters 2 and 3) were collected and tested for IBR antibody by SN assay. All samples were negative for IBR antibody (SN<1:2). 1128 calves completed the study 28 days post parturition. Common respiratory and enteric diseases were diagnosed and treated. Calf mortalities were 26 from control heifers and 29 from vaccinated heifers an overall rate of 5.05%.
Significance:
The primary outcome was satisfied by demonstrating that the 5-way MLV intranasal vaccine containing IBR does not cause a greater abortion rate in vaccinated heifers compared to the abortion rate of nonvaccinated controls when administered at each stage of the 3 trimesters of pregnancy. Results demonstrate no impact on heifer health, abortion rate, or newborn calf health up to 28 days of age including no IBR antibody titers if pre-breeding vaccinated pregnant heifers are inoculated with a 5-way IN vaccine containing modified live IBR virus. This MLV intranasal vaccine is safe for pregnant cows previously vaccinated with MLV IBR and the calves nursing pregnant cows.
