Modified-live vaccines must be handled and stored properly if they are to be efficacious. This article and a YouTube video cover basics that are helpful for newbies and old hands alike.
Source: Bovine Veterinarian, July 3, 2019. Link. Incorrect storage, exposure to sunlight and delayed administration all can reduce or even eliminate the effectiveness of an MLV, cautioned New Mexico State University Extension Animal Scientist Manny Encinias. He provides measures to ensure MLVs are adequately protected to deliver the intended live dose of modified virus when they reach each calf.