Be aware that anaphylactic (allergic) reactions are always possible when administering vaccines and be prepared with at least some epinephrine available.
Recent work has demonstrated that vaccines prepared from gram negative bacteria may contain sufficient amounts of endotoxins to cause clinical problems. Lepto, campylobacter,
salmonella, E. coli and pasteurella vaccines could all be potential problems. It has been recommended that not more than two of these products be administered at one time.
Cattle tend to hold their body heat in hot weather and may be severely stressed by working them later in the day when it is hot and humid. Cattle should be worked in the early morning while it is cooler. Avoid working cattle if the temperature is over 85 degrees Fahrenheit with over 40% humidity, or at higher temperatures with lower humidity.
It has recently been reported that the use of an injectable type of MLV-IBR vaccine in calves under 5 days of age may result in a massive infection by this herpes type one virus. If calves are to be vaccinated at less than 5 days of age, the intranasal product should be used. Even for calves less than three months of age the intranasal product tends to give the best results because it is less affected by colostral immunity.
Source: Clell V. Bagley, DVM, Extension Veterinarian Utah State University, Logan UT 84322-5600