[Investigation on the cold-chain temperature of vaccine in some areas of Zhejiang Province]

Objective: To investigation the situation of cold chain on vaccine in parts of Zhejiang Province and to provide recommendations for the management. Methods: From October to December, 2016, we each selected an immunization clinic in Cangnan County of Wenzhou, Yongkang City of Jinhua, Jianggan District of Hangzhou. Temperature recorder and vaccine viral monitor (VVM) labels were used to monitor the cold chain during all the storage and transportation process. In Jianggan District, we use optical density sensor to detected 20 VVM labels every time when the vaccine was stock in and out. Results: In total, 54 958 records were collected by temperature recording devices in all the three immunization clinic. 275 records exceeded the temperature limit required for store and transportation, of which 270 (98.2%) were above 8 ℃ and 5 (1.9%) were under 2 ℃. Excessive temperature exposure mainly occurred during the transportation (38.2%, n=105), followed by storage process in CDCs at different levels (26.2%, n=72), stock in and out (20.7%, n=50) and storage in the refrigerators in immunization clinics (14.9%, n=41). The average optical density difference between VVM labels and the reference circular decreased from 0.404 to 0.344 when the vaccines were delivered from the Zhejiang provincial CDC to immunization clinics. The color of VVMs did not significantly changed before use. Conclusions: The potential risk of vaccine cold chain in the monitoring sites is over-temperature. The weak links of cold chain management include the transportation, storage process, and stock in and out.