Vaccine Refrigerator Regulator with Data Logger & Back-up Power Supply

Introduction

Many vaccines require a storage temperature between 2-8 °C throughout thesupply cold chain. Multiple studies conducted at healthcare facilities worldwide document an endemicfailure to properly store vaccines, risking the efficacy of local vaccination programs.This “weak link” at the end of the cold chainis largely due to both the widespread use of inadequate domestic refrigerators for vaccine storage, and electrical power interruptions. The required specialized refrigeration equipment and backup power systemareboth prohibitively expensive for smaller facilities. Prompted by this finding, the authors sought an affordable solution for small-scale vaccine storage applications.

Methods

The solution presented is an aftermarketappliance designed toaccompany a wide range of domestic refrigerators.After undergoing an initial calibration step, the device effectively overridesthe refrigerator's native thermostat(s) and assumes thermoregulatory control. All interfaces between the device and the refrigerator are strictly external, allowing for installation by a layperson. Wireless temperature sensor measurements are frequently logged to a removable USB thumb drive to provide vaccine temperature traceability. The device is further equipped to charge an external battery while grid power is available, and upon grid failure automatically source refrigeration power froman attached external inverter.

Results

The regulator device successfullymaintained a 2-8 °C environment for all properly stored vaccine vials. Furthermore, it successfully adapted to and compensated for the individual operational characteristics of various refrigerators, and flagged those unsuitable for vaccine storage. Back-up power outage resiliency is recorded at16-25 hours for 18-28ft³sized household refrigerators using a 160Ah battery.The cost of manufacturing the device is estimated at $250 per unit.

Discussion

The Baylor/Rice regulator device provides an affordable refrigeration control and temperature monitoring system suitable for converting household refrigerators into effective vaccine refrigerators. The device will also be useful in areas subject to electrical grid failure.