Assessment of the Immunogenicity of COVID-19 Heterogeneous Booster Vaccination Following the Full Immunization of Inactivated Vaccines

Objective: To study the immunogenicity of COVID-19 (Corona Virus Disease 2019) booster vaccines, produced via different technical routes, following the first two doses of inactivated COVID-19 vaccine. Methods: A total of 320 healthy subjects, aged 18 to 59 years old, who had already received the first two shots of the inactivated COVID-19 vaccine were recruited. They were randomly divided into four groups (A, B, C, and D), with 80 subjects in each group. These subjects then received a booster dose of the same inactivated COVID-19 vaccine as in the first two shots, or a booster dose of a different inactivated COVID-19 vaccine, adenoviral vector vaccine, and recombinant protein vaccine (CHO cells). Blood samples were collected before the booster immunization and on days 14 and 28 after booster immunization, to determine the level of neutralizing antibodies. Results: There was no statistically significant difference between the four groups in age or gender between all four study groups (p > 0.05). All four groups showed a significant increase in COVID neutralizing antibody level on day 14 and day 28 (p < 0.05). Group C and group D showed a significant increase compared with group A or group B (p < 0.05). And, the highest GMT (geometric mean titer) level was observed in group C on day 14 among all four groups and all three time points. The antibody positive conversion rate was 100% on day 28.Conclusions: A booster dose of heterologous COVID-19 vaccine six months after the first two shots led to significantly higher immunogenicity than when the same type of vaccine used for basic immunization was used for the booster. Heterologous booster immunization is of high importance for raising the immunization efficiency.

Automated summary

The study investigates the immunogenicity of COVID-19 booster vaccines produced via different technical routes after the administration of the first two doses of an inactivated COVID-19 vaccine. A total of 320 healthy subjects were recruited and randomly divided into four groups. The results showed that booster immunization with a heterologous COVID-19 vaccine led to significantly higher immunogenicity compared to using the same type of vaccine for basic immunization.