A temperature excursion doesn't announce itself with much warning. A door left ajar, a compressor that fails overnight, a power outage during a weekend nobody was watching. Suddenly you're looking at a storage unit full of vaccines or perishables that may or may not still be viable. What you do in the next few minutes matters a lot.
A temperature excursion is any temperature reading outside the ranges specified in a product's manufacturer package insert. For vaccines, the CDC defines standard refrigerated storage as 2°C to 8°C (36°F to 46°F) and frozen storage as -50°C to -15°C (-58°F to +5°F). For food service, the FDA's Food Code requires cold food to be held at or below 41°F and hot food at or above 135°F.
Even a brief excursion can reduce or destroy potency. A compromised vaccine may leave a patient unprotected. Food that drifts out of safe temperature range creates a foodborne illness risk. And for facilities enrolled in programs like Vaccines for Children (VFC), a poorly documented excursion can put that enrollment at risk.
Most excursions are preventable, and most trace back to one of a handful of root causes:
The last point is worth sitting with. Manual logging catches excursions only when someone is there to check. Most excursions happen when nobody is looking: nights, weekends, holidays. A continuous automated monitoring system is the only way to have visibility 24 hours a day.
These steps are based on the CDC's Vaccine Storage and Handling Toolkit (2024 edition) and apply to both vaccine and food cold chain excursions.
Anyone who hears an alarm, receives an alert, or notices an out-of-range temperature reading should notify the primary vaccine coordinator or their supervisor immediately. Don't wait to see if temperatures self-correct. Time matters. The longer a product stays out of range, the more compromised it becomes, and the harder it is to establish a clear timeline for documentation.
Label all exposed vaccines or food products "DO NOT USE" and move them to a separate area within the storage unit, or to a separate cooler or container. Do not discard anything yet. You'll need the products on hand for assessment by the manufacturer or immunization program, and discarding before getting guidance could result in unnecessary waste, or worse, losing the ability to claim replacement value.
This step is where many facilities fall short, and it's the one that matters most for compliance. Your documentation of the event should include:
If you have a digital data logger (DDL), pull the temperature history log immediately. This gives you a precise, timestamped record that's far more defensible than manual notes. The CDC recommends DDLs record at minimum every 30 minutes, with a buffered probe that best reflects actual product temperatures.
This isn't a call you should make on your own. Contact your state or local immunization program for vaccine excursions, or the product manufacturer directly. Be ready to share your full documentation: temperatures reached, duration of excursion, and the specific products affected. They will advise whether products can still be used, need to be destroyed, or require patients to be recalled for re-vaccination.
Follow your facility's Standard Operating Procedures (SOPs) to bring the storage unit back to the correct temperature range. At minimum, check that the temperature monitoring device is properly placed. For vaccines, the CDC requires a buffered probe positioned in the center of the unit, away from walls, vents, and the door. Verify the unit is holding stable before returning any products.
If the cause of the excursion was equipment failure, do not assume the problem is fixed just because temperatures read normal. Have the unit inspected before relying on it again for critical inventory.
Close out the incident report: what happened to the affected products, what you did and when, who you called and what they told you, and what you've changed to prevent it happening again. Some state immunization programs, including Indiana's, require proof of at least five days of in-range temperatures and a formal root cause analysis (RCA) after any excursion that causes vaccine loss.
This final step is the one most facilities skip or rush, and it's the one that determines whether the same excursion happens again.
Everything above applies to food service cold chain as well. The stakes are different. Food excursions don't carry the same VFC compliance risk as vaccine excursions, but the consequences are still real. Food that leaves the safe temperature zone can trigger foodborne illness, fail a health inspection, or require disposal of expensive inventory.
The FDA Food Code requires cold food to be held at or below 41°F and establishes a "danger zone" of 41°F to 135°F where bacterial growth accelerates rapidly. For food service operators, the same principles apply: monitor continuously, document excursions promptly, quarantine affected products, and get guidance before making disposal decisions.
Demand for refrigerated and frozen food is rising fast. A 2026 Lineage Logistics survey found 72% of organizations reported increasing demand for temperature-controlled products. More volume moving through cold chain means more opportunities for something to go wrong.
The six steps above are for after something goes wrong. The goal is to need them as rarely as possible. A few practices that make the biggest difference:
A temperature excursion is any temperature reading outside the range specified in a product's manufacturer package insert. For vaccines, the CDC defines acceptable refrigerated storage as 2°C to 8°C. For food, the FDA Food Code requires cold foods to be held at or below 41°F. Any deviation from these ranges requires immediate action and documentation.
Notify your supervisor or vaccine coordinator immediately. Do not wait to see if temperatures self-correct. Then quarantine all affected products by labeling them "DO NOT USE" and separating them from unaffected inventory. Do not discard anything until you've received guidance from the manufacturer or your state immunization program.
Sometimes, but never assume. Viability depends on the specific vaccine, how far temperatures deviated, and how long the excursion lasted. Contact your state or local immunization program or the vaccine manufacturer directly with full documentation of the event. They will advise on whether vaccines are still usable or whether patients need to be recalled for re-vaccination.
At minimum: the date and time of detection, the name of the person reporting, an inventory of affected products, minimum and maximum temperatures recorded, the duration of the excursion, and any prior issues with the storage unit. Digital data logger records are the gold standard because they provide a precise, timestamped history that is far more defensible than handwritten logs.
The most common causes are equipment failure (compressor or door seal issues), power outages, human error such as doors left ajar or incorrect thermostat settings, and gaps in monitoring, particularly overnight and on weekends. Most excursions are preventable with continuous automated monitoring, regular equipment maintenance, and a written emergency response plan.
The highest-impact prevention measures are continuous digital monitoring with real-time alerts, regular equipment maintenance, a written emergency response plan that staff know before an event occurs, and consistent review of temperature logs at least every two weeks. For VFC providers, the CDC requires digital data loggers that record at minimum every 30 minutes with a buffered probe.