Ask the Vet

Modified Live Vaccines

There are risks and benefits to vaccinating cows, especially when pregnant. The biggest risk for any operator, however, is an inferior vaccination program. (DTN/Progressive Farmer photo by Gregg Hillyer)


My veterinarian switched me to a program where I can use modified live vaccines in my pregnant cows. We have had no problems, but I'm concerned because I've read this can cause abortions. Should I stop this program and go back to killed vaccines?


This is about risk management. Studies show higher levels of both respiratory and reproductive protection with modified live vaccines (MLV) over their killed cousins. MLVs are also typically less expensive, and are safe when used according to label directions. When selecting a vaccine, be sure it provides fetal protection against bovine viral diarrhea (BVD). Boehringer Ingelheim's Express FP and Pfizer's Bovi-Shield GOLD FP or PregGuard GOLD FP are labeled for us in pregnant cows.

If you intend to use MLVs in this manner, do it correctly. To safely transition, the entire cow herd must be vaccinated while open with one of these products. Heifers receive at least two doses, one dose about 30 days prebreeding. Pregnant cattle can then be given one of these products within 12 months of the last dose. For many producers, this transition is worth the effort in order to vaccinate pregnant cows at a time that better fits their management programs.

Is there risk? Maybe. Vaccinating cows when they are pregnant may not be ideal. But in my opinion, there is more risk in an inferior vaccination program. For the best reproductive protection, I personally prefer vaccinating cows after calving and three to four weeks prebreeding.

So back to the question of risks versus benefits. You and your veterinarian have to make that call. Whatever you do, read, understand and follow the label precisely.

Please contact your veterinarian for questions pertaining to the health of your herd. Every operation is unique, and the information in this column does not pertain to all situations.