ABSTRACT
@#Objective To investigate the titer stability of the harvest solution of severe acute respiratory syndrome coronavirus2(SARS-CoV-2)at 2 ～ 8 ℃ and the inactivation effect of β-propiolactone inactivator on the virus.Methods Three batches of SARS-CoV-2 harvest solution(batch numbers:202111001,202111002 and 202111003)were stored at 2 ～ 8 ℃ for 12 d and sampled every 3 d(0,3,6,9 and 12 d)for detection of the titers by Karber method;Three batches of virus harvest solution equilibrated overnight at 2 ～ 8 ℃ were inactivated by adding β-propiolactone at a volume fraction of 1∶4 000 and detected for the titers at different inactivation time points(0,0.5,1,1.5,2,3,4,8,16 and 24 h),of which samples inactivated for 8,16 and 24 h were taken for inactivation verification,and samples inactivated for 24 h were observed by transmission electron microscope.Results The titers of SARS-CoV-2 decreased with the prolongation of storage time at 2 ～8 ℃,which showed no obvious decrease during 0 ～ 3 d,while decreased from the initial 7.75,6 and 7.5 lgCCID_(50)/mL to5.75,4.625 and 6.25 lgCCID_(50)/mL on day 12,indicating that the virus activity showed a gradual decrease trend at 2 ～8 ℃；With the inactivation time,the virus titer decreased continuously and could not be detected after inactivation for 3 h.Transmission electron microscope observation showed that the inactivated virus particles were intact and the spike protein was evenly distributed.Conclusion The virulence of SARS-CoV-2 stored at 2 ～ 8 ℃ was unstable,so the subsequent inactivation and purification process should be carried out as soon as possible;The titer of virus could not be detected after3 h of inactivation,which provided a reference for the determination of the inactivation process.
ABSTRACT
Objective @# To evaluate the safety and immunogenicity of a split-virion quadrivalent influenza vaccine.@*Methods @#The healthy people aged three years or over in Wuyang County and Xiping County of Henan Province were divided into the experimental group, control group 1 and control group 2, and were vaccinated with split-virion quadrivalent influenza vaccines, split-virion trivalent influenza vaccines (without B/Victoria) and a split-virion trivalent influenza vaccines (without B/Yamagata) , respectively. The hemagglutination inhibition (HI) antibodies were detected before and after immunization. The incidence rate of adverse events following immunization (AEFI) , HI antibody positive conversion rate, the protection rate of HI antibodies and the growth of geometric mean titer (GMT) were calculated and compared with the standard of Food and Drug Administration (FDA).@*Results@#Totally 2 924 people were recruited, with 975 in the experimental group, 974 in the control group 1 and 975 in control group 2. The incidence rate of AEFI in the experimental group was 11.7%, higher than 7.9% in control group 1 and 8.8% in control group 2 (P < 0.05) during 30 minutes and 8 days after inoculation. The positive conversion rates of HI antibodies of H1N1, H3N2, By and Bv in the experimental group were 78.5%, 53.3%, 78.3% and 62.9%, respectively. The rate differences of the positive conversion rates of HI antibodies of By between the experimental group and control group 2, and of Bv between the experimental group and control group 1 were 42.1% (95%CI: 38.0%-46.2%) and 33.2% (95%CI: 28.9%-37.5%) , with both lower limits of 95%CI more than -0.10. The GMT increase of HI antibodies was more than 2.5 times in the three groups. The protective rates of HI antibodies of H1N1, H3N2, By and Bv in the experimental group were 87.7%, 98.7%, 93.6% and 77.2%, respectively. The protective rates of HI antibodies of By in control group 2 and Bv in control group 1 were 71.1% and 51.0%, both lower than those in the experimental group (P < 0.05).@*Conclusions @#After the inoculation of the quadrivalent influenza vaccine, the positive conversion rates (>40%) , protection rates (>70%) and GMT increase (>2.5 times) of HI antibodies of H1N1, H3N2, By and Bv all meet the quality standards of FDA. The safety and immunogenicity of the quadrivalent influenza vaccine are not inferior to those of the trivalent influenza vaccine.