Monitoring analysis of the titers of varicella attenuated live vaccines in Minhang District, Shanghai / 中华微生物学和免疫学杂志

ABSTRACT

Objective To measure the titers of varicella live attenuated vaccines ( VarV) during the process of transportation and storage in different seasons and communities of Minhang Distract, Shang-hai, to evaluate the operation of cold chain system and the thermal stability of vaccines and to provide refer-ences for the management, introduction, research and development of vaccine in future.Methods Four communities with high outbreak rates of varicella during 2012 to 2013 and four communities with low out-break rates were randomly selected from 13 communities in Minhang District, Shanghai.The titers of VarVs were detected by using the quantitative plaque assay before and after 30 days of storage in November 2013 and February, May, August 2014.Results The overall rate of qualified VarVs was 90.63% with a geo-metric mean titer (GMT) of 3.67 (LgPFU/0.5 ml).96.88%of the VarVs produced by company C met the quality standard with a GMT of 3.89 ( LgPFU/0.5 ml) followed by those produced by company B with a rate of 91.67%and a GMT of 3.75 ( LgPFU/0.5 ml) .The rate of qualified VarVs produced by company A was the lowest, which was 80.00%, with GMT of 3.29 (LgPFU/0.5 ml).There were significant differences in the rates of qualified VarV among the three companies (χ2=8.288, P=0.016).The rate of qualified vac-cines in communities close to the Shanghai Minhang Center for Disease Control and Prevention ( Minhang CDC) was 91.67%, while 100%of the vaccine samples collected form the communities at a middling dis-tance from or far from the Minhang CDC met the quality standard.No significant difference in the rate of qualified vaccine was found among the three types of communities (χ2=3.441, P=0.179).The quarterly rates of qualified vaccines produced by B and C companies were 100%except for the third quarter.The rates of qualified vaccines produced by A, B and C companies in the third quarter were respectively 70.00%, 66.67%and 87.50%.No statistical differences in the quarterly rates of qualified vaccines were found among the three companies (χ2=1.25, P=0.7412;χ2=6.545, P=0.088; χ2=6.194, P=0.103).No statistical differences in the rates of qualified vaccines before and after 30 days of storage were found among the three companies (χ2=0.625, P=0.347;χ2=0.000, P=1.000;χ2=2.065, P=0.492).Conclusion A well-managed and-operated cold chain system was implemented in Minhang District in the storage and transport of vaccines as well as other related links.The thermal stability of vaccines produced by company C was better than those of the other two companies.A surveillance for the titers of vaccines produced by com-pany A should be strengthened.