Chances are, when you purchased a new refrigerator for the house, you moved the old one to the barn. Problem is, in addition to being worn out, these old units can be very inefficient compared to modern refrigerators. They freeze items placed near the rear element; in the summer, they barely keep cool because the doors don't seal well.
Freezing is one of the worst events that can happen to livestock pharmaceutical products. It's something that can easily happen to everything in the old 'fridge over a large part of the country during the winter.
The above scenario is much too often the case, says Ron Torell, University of Nevada (UN) Cooperative Extension livestock specialist.
“Improperly stored vaccines are a leading cause of immune response failure,” he says. “Not only can this mean money down the drain, but when we use these improperly stored vaccines, we get a false sense of security that our cattle are protected.”
Most labels suggest storing vaccines between 35°F and 45°F.
“Temperatures above or below those recommended on vaccine labels will adversely affect all vaccines, killed or modified-live,” says Mike Lathrop, Pfizer Animal Health technical services veterinarian. “The impact depends on the vaccine, and the duration and degree of variance.”
Killed vaccines, as well as many modified-live vaccines, include an adjuvant to enhance the immune response. When vaccines with an adjuvant freeze, the adjuvant, or portions of the adjuvant, usually separate from the antigen(s) in the vaccine.
“The result is we can no longer expect or have confidence the vaccine will function to the level of the efficacy claims stated on the label,” Lathrop adds.
David Thain, DVM, UN Extension veterinarian, says there's also the possibility this may increase the amount of free endotoxin in a bacterin. This can increase the potential for adverse reactions.
“We recommend throwing vaccines out that have reached temperatures outside the ranges recommended on the label,” Thain says.
Field fridge study
During 2005-2006, UN Extension conducted a field study of refrigerators used by ranchers. They evaluated the suitability and effectiveness of these vaccine storage facilities.
The researchers found 25% of the refrigerators failed to maintain vaccines in the safe range. Several refrigerators actually froze vaccines to 10°F for an extended period of time. The refrigerators that froze vaccines in winter allowed heating to unsafe levels during summer. In another part of the study, 100% of “feed store” refrigerators maintained adequate temperatures during the entire period.
“Even if you purchase a good refrigerator for the barn, an extended subzero cold spell will freeze everything if the unit isn't in a heated room,” Torell explains. “Turning the refrigerator off will do no good. If the ambient outside temperature is zero degrees for an extended period of time, the refrigerator will not maintain temperatures within the safe range.”
He also warns that a refrigerator that's seldom opened will creep down in temperature, just like a refrigerator that's continually opened will creep up in temperature. Vaccines stored on the door will be warmer, while vaccines near the freezer compartment will be colder.
A good refrigerator stored in an environmentally controlled room is a must. A thermometer that records minimum and maximum temperatures can be purchased for $14 and allows monitoring of pharmaceutical products in storage.
Torell also recommends buying only enough pharmaceutical products for your immediate needs.
“This is going to require advanced planning and ordering of vaccines,” he says. “But a little attention to the seemingly minor detail of proper vaccine storage can pay big dividends.”