Rapid development in medical research and mass vaccination depends heavily upon the high immunization coverage of the target group and vaccine inventory management, including suitable storage conditions and handling of vaccines. Therefore, one of the critical functions of the vaccine supply chain is to keep vaccine products properly refrigerated at every step in their journey. Monitoring and Alarming is an essential part.

Vaccines are sensitive biological substances that can lose their potency and effectiveness if they’re exposed to temperatures (heat or cold) outside the required temperature range of +20C to +80C, with few exceptions or when exposed directly under sunlight. In general, whenever cold chain capacity permits, WHO recommends that both diluents and their corresponding vaccines be stored and transported together in the cold chain, making stock management more manageable and reducing the risk that diluents will become separated from the vaccines to which they belong. The package insert should provide the lower and upper-temperature limit

Maintaining proper temperatures for the product that can tolerate neither excessive heat nor cold is difficult in practice- especially in places with extremely hot or cold climates, unreliable connections to electricity. Temperature monitoring and Alarming System, then, is a demanding tool to assess vaccine handling quality, detect malfunctions in parts, and prevent any temperature fluctuations than calibrated levels.

Heat Sensitivity of Vaccines

Monitoring and Alarming

All most of the vaccines lost their potential over time where this potential is accelerated by heat. The sensitivity of vaccines varies based on their types. Whereas the diluents also known as pharmacological inactive are more heat stable than the vaccines so are packed separately. These diluents could be stored at room temperature.

On the other hand, the Pharmacological active diluents are heat sensitive and should be packed in the same secondary cartoon. All the diluents must be kept in between the temperature of +2°C and +8°C at the time of storage.

Freeze Sensitivity of Vaccine

Many of the Vaccines could tolerate the freezing but on the other hand, it could also damage the quality of the vaccine. Freezing can damage the vaccine containing the Aluminium salt adjuvants. The immunological properties of vaccines are adversely affected when the vaccines are frozen.

Photosensitivity of Vaccine

Some vaccines lose potency when exposing to ultraviolet light. So, these vaccines are packed ad supply in vials made of dark glass. Vaccines should be protected from the sunlight and the UV emitting artificial light sources.

A temperature monitoring device is an essential requirement for vaccine temperature monitoring. Well-maintained records can be used to assess the quality of the vaccine supply chain, monitor the performance of cold chain equipment, and demonstrate compliance with good storage and distribution practices.

The aim of the monitoring and record-keeping should achieve the verification that the vaccine storage temperature is within the acceptable range of the temperature between +2°C to +8°C and vaccine refrigerators and -25°C to -15°C in freezer rooms. The monitoring devices should also be able to detect the out-of-range storage temperature for taking corrective action.

There is the requirement for a continuous temperature monitoring system for the primary vaccines.

WHO recommends temperature monitoring devices based on the specific cold chain equipment application and the intended monitoring purpose?

There is a rapid growth in the temperature monitoring system. The availability of these devices is extending although the durability and the performance quality of the devices are not known. So, there is the constant monitoring of the market by the WHO and is updating the performance specification periodically for reflecting the changing technological development and the need and demand of the users. Various devices are developed based on their uses. Some devices are used in a fixed location for storage, some are used for transportation of the vaccines and some are multi-working devices that could be used for both storage and transportation.

Figure 1: Source Google

medical montioring


Nowadays, programmable electronic temperature and event logger systems are the best

the choice for any primary and subnational stores. There should be temperature sensors in every cold storage or room, vaccine refrigerator, freezer room. These sensors are to be monitored via computer-based wired or wireless connections. The central data storage system helps in analyzing the temperature records electronically helping in generating periodic reports. This systematic report analysis is much better and effective than the manual reviewing process.

Event logger systems can also be configured with sensors that monitor door openings as well as other performance characteristics such as relative humidity and voltage fluctuations. Those system needs to be equipped with the local alarms and the alarm strobes that helps in sending the alerts for respective users, SMS and email enable devices in case of temperature and other parameters are above or below the predefined limits. While for the remote motoring and alarm reporting from various sites, the internet, and the intranet connectivity system could also be used.

These multi-sensor event logger systems require site-specific configuration, installation, and commissioning. Temperature sensors should be placed at the threshold temperature points representing high and low-temperature extremes. These points should be generated at the time of installation by temperature mapping. Besides this, all cold rooms and freezer rooms require a reliable backup device to monitor temperatures in case the event logger system fails.

Integrated digital thermometers are built in the refrigeration unit as these devices required a power source. The fixed gas pressure dial thermometer doesn’t require the power supply which is the only fail-safe option. In addition, 30-day electronic temperature recorders and electronic freeze indicators are sometimes used for backup. However, these devices should never be used to replace a programmable electronic temperature and event logger system, and their routine use to locate hot and cold spots in a cold room is not a substitute for a properly conducted temperature mapping exercise.

Studies in both industrialized and developing countries have revealed that vaccines are commonly exposed to damaging temperatures, especially exposure to sub-zero temperatures. The simplest way to identify these risks is to conduct a systematic temperature monitoring study of the entire vaccine supply chain designed to identify the sources of damaging temperature exposure.