Evaluation Of Immunogenicity Of Different COVID-19 Vaccines And Vaccine Boosters Study Of Vaccination Strategy

Since the first report on December 2019,the SARS Co V-2 has been widely spread around the world,and the virus continues to mutate under the pressure of selection.New mutants,such as Omicron,have immune escape against COVID-19 vaccine,which greatly reduces the protective effect of existing vaccines.As of May 17,2022,China has approved the emergency use of COVID-19 inactivated vaccine,adenovirus vector vaccine and recombinant protein subunit vaccine,but there is no systematic comparison on the persistence of antibody levels of these vaccines in humans.In addition,studying how to conduct intensive vaccination after the antibody level drops is of great significance for improving the cross humoral immune response of the population to the mutant strain and responding to the infection of the mutant strain.In this study,a total of 316 individuals who received inactivated vaccines and 322 individuals who received adenovirus vector vaccines were collected.Their antibody levels after 1,3,and 6 months of basic immunization were continuously tracked and investigated.The binding antibody levels of SARS-Co V-2 wild-type RBD in the subjects’ serum were detected through enzyme-linked immunosorbent assay to understand the persistence of antibody levels;Then,we evaluated the humoral immune response of sequential immunization with different COVID-19 vaccines after 6 months of basic immunization when the level of antibody in vivo dropped;Finally,in vivo experiments were conducted using a mouse model to evaluate the cross immune response of m RNA vaccines designed based on different variants of RBD to Omicron BA.1 variant after basic immunization.The results showed that after 1,3,and 6 months of basic immunization with adenovirus vector vaccines or inactivated vaccines,there was a significant and sustained decrease in the serum binding antibody levels of the subjects;In addition,after basic inactivated vaccines,adenovirus vector vaccines,or recombinant protein subunit vaccines,the antibody levels against Omicron RBD decreased compared to wild-type RBD.However,after 4-8 months of basic inactivated vaccines or adenovirus vector vaccines,sequential immunization with adenovirus vector vaccines or recombinant protein subunit vaccines increased the highest antibody levels;Finally,after the initial immunization of m RNA vaccines based on the S-protein encoding of the prototype strain in a mouse model,only the neutralizing antibody levels elicited by m RNA vaccines based on Omicron RBD encoding were significantly higher in sequential immunization of m RNA vaccines designed based on different variant strains of RBD than those elicited by the prototype strain of RBD enhancer.In summary,after 6 months of basic immune inactivated vaccines or adenovirus vector vaccines,antibody levels significantly decrease,and booster immunization should be carried out;Secondly,the antibody levels stimulated by basic immunity are insufficient to cope with Omicron infection,and booster vaccination should be administered.However,after 4-8 months of inactivated basic immunity vaccines or adenovirus vector vaccines,sequential immunization with adenovirus vector vaccines or recombinant protein subunit vaccines has the best humoral immune effect;Finally,in the mouse model,the sequential immune Omicron variant vaccine has the best effect on Omicron,but due to the presence of immunoblotting,the neutralizing antibody level against the prototype strain is higher.