An aspect of good preventive medicine in the cow-calf herd focuses on protecting the young calf from diseases they may encounter while on summer pasture. Cow-calf producers, with input from their veterinarians, typically vaccinate calves going out to pasture in the late spring. Most commonly, 7-way Clostridial vaccines providing protection against blackleg are used, but depending on individual herd issues, vaccines against illnesses such as pinkeye or respiratory diseases might be considered.
When groups of calves on pasture experience respiratory disease on pasture before weaning, vaccines against viral pathogens such as IBR, PI3 and BRSV are often considered in spring calf programs. Vaccines against these pathogens come in injectable as well as intranasal formulations. How do intranasal vaccines work, and how do they differ from injectable vaccines?
When an intranasal vaccine is squirted up the nose, several things happen. Probably the most important is that the vaccine stimulates a lot of surface or “mucosal” immunity in the nose and upper respiratory tract. When you think about it, this might be the most important part of the body in which to stimulate immunity. Essentially all respiratory germs enter a calf through the nose. If the immune system can eliminate or limit the germ in the nasal passages, then those pathogens won’t reach the lower lungs, where they really do their damage.
All vaccines stimulate the immune system by helping the body produce antibodies against a specific germ, and also by stimulating immune system cells to help recognize and destroy cells that have been infected by viruses. In the case of intranasal vaccines, a lot of that antibody production takes place in the lining of the respiratory tract, in the fluids that cover and bathe the inside of the nose, throat, and windpipe.
The nasal passages are also areas of the body that contain a lot of “dendritic cells.” These are specialized body cells that lay right under the lining of the upper respiratory tract. They can travel from the site of an immune stimulus (like where an intranasal vaccine has been squirted) to lymph nodes, activating an even broader immune response throughout the body.
In addition, researchers also find that following administration of an intranasal vaccine, a lot of a substance called “interferon” is produced locally. Interferon is a body chemical that non-specifically helps the immune system; in other words, it helps fight off germs that are not necessarily included in the vaccine. Due in large part to this local action, the immune response seems to respond quicker to intranasal vaccines compared to injectable vaccines.