Vaccine ‘myth-takes’: Common myths, mistakes about vaccines

By Kayla Jentz


Three vaccination program trends – driven by a handful of myths – negatively impact effectiveness and add herd health risks. 


You have a vaccination program set up. You vaccinate according to your farm’s guidelines, and you’re pretty sure you have everything properly vaccinated from calf to cow. So, you should be covered, right? 

In many cases, the answer is no, you might not be adequately protected against disease, according to Dr. Vic Cortese, Director of Cattle Immunology and Biologics with Zoetis. He sees three major trends when it comes to vaccination programs. 

“We tend to over-vaccinate; we don’t evaluate our vaccination programs often enough to keep up with change; and we don’t coordinate our vaccination program starting with the calf and going all the way up to the cow,” Cortese told attendees at the 2013 Central Plains Dairy Expo, in Sioux Falls, S.D.

Cortese discussed myths regarding vaccines, and what those myths mean for dairy operations.


Myth 1: A USDA license means the vaccine will work the same in all cattle.

Unfortunately, just because a product is licensed and available doesn’t mean it works, according to Cortese. Reasons the vaccine might not be effective include: using the vaccine on the wrong age of animal or incorrect species; measuring the wrong disease outcome; having a disease challenge that overwhelms the vaccine, or the vaccine label isn’t high enough to be effective.

He recommends comparing vaccines and reading the labels to determine a product’s potential performance. 

The top five label claims are:

1) Prevention of infection;

2) Prevention of disease; 

3) Aids in disease prevention (the most common label claim);

4) Aids in disease control (animals may still die); and 

5) Other claims.


Myth 2: Vaccinated animals are protected animals.

“Compliance and proper vaccine handling/administration are two of the biggest challenges in dairy vaccination programs today,” said Cortese.

He encouraged producers to evaluate: Are the vaccines even being administered? Are vaccines being stored properly? How are vaccines being handled once removed from the refrigerator? 

Cortese referenced a herd he worked with that purchased all vaccines for the year based on calculations for how much they should be using. At year’s end, the dairy had a large supply of unused vaccines, indicating employees were not vaccinating, although records indicated they had.


Myth 3: Annual vaccination means one year of immunity.

According to Cortese, “annual” means you don’t know exactly how long it lasts. USDA doesn’t require duration of immunity studies (aside from rabies vaccinations). Studies that are successful 14-35 days after vaccination are automatically given annual revaccination labels.

Producers should work with their veterinarian to determine when revaccination should occur if a duration of immunity claim isn’t provided by the manufacturer.


Myth 4: The higher the antibody/titer levels, the better the protection level.

Titers may be a poor indicator of protection, other than in colostrum.


Myth 5: Vaccines may not be effective in young calves because they are blocked by maternal antibodies.

Some are, while some are not, Cortese said. The answer is not clear cut and varies by disease, type of vaccine, preexisting antibody levels and other factors. If it’s a concern, he suggested asking to see studies done in calves with maternal antibodies.


Myth 6: The more vaccines I can give at one time, the less stress there is on the animal.

Large combinations of vaccines are very dangerous in dairy breeds, Cortese said. Animals can have adverse reactions, and extreme temperatures can increase the risk of a reaction. Cortese recommends giving no more than two gram-negative vaccines per day, no vibrio-lepto combinations, and giving SRP vaccines by themselves.

He also recommended avoiding vaccination on days when it is 85° F or higher, which could increase the possibility of adverse reactions. Additionally, move fresh cow shots back as far as possible to allow the cow’s immune system time to recover after calving, and during the first week of a calf’s life, only give an oral or intranasal vaccine.


Dr. Vic Cortese is Director of Cattle Immunology and Biologics with Zoetis. Contact him via email at