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Through the eyes of a specialist: immunogenicity, safety of the third dose and vaccination on specific populations during the third day of the CoronaVac Symposium

Publicado em: 01/01/1970

On the third day of the International Symposium regarding CoronaVac, the speeches touched the subjects of immunogenicity and safety studies about the third dose of the CoronaVac vaccine. During this morning were also discussed the effects of vaccination on specific populations like: children and teenagers, eldelry, immunocompromised and individuals with comorbidities.


Speech title: Immunogenicity and immune persistence of the third dose of CoronaVac on healthy adults

Doctor Hongjie Yu, professor of the Health Public School from the University of Fudan in China, began the speeches cycle of the third day of the Symposium. During his presentation, Dr. Yu emphasized the results of the immunogenicity of the third dose from CoronaVac, administered 2 or 8 months after the second dose of the vaccination, on healthy individuals of the age groups from 18-59 years of age and above 60 years. Similar to what was observed in the scheme of two doses, the third dose of the CoronaVac did not cause serious adverse effects, only mild reactions (Level 1 or 2), being the most frequent the pain in the area of the injection. Among the presented results, according with other studies, was in evidence the decrease in the production of neutralizing antibodies 6 months after the second dose. However, the administration of the third dose of CoronaVac 8 months after the vaccine scheme, resulted in an increase of 3-5 times in the production of the neutralizing antibodies, with a long term response, in the group aged 18-59 years and 60 years older.


Speech title: Multicentric study, randomized, double-blinded, placebo controlled phase 3 to evaluate the efficacy, immunogenicity and safety of the CoronaVac vaccine on children and teenagers of age from 6 months to 17 years

Doctor Susan Bueno, professor at the Pontifical Catholic University from Chile and associated researcher of the Millenium Institute of Immunology and Immunotherapy, presented results that make part of a clinical multicentric study of phase 3 with 14 thousand of children and teenagers from 6 months of age to 17 years of age in Chile, Quenya, Malaysia, Philippines and South Africa. The results presented by doctor Susan referred to the chilean volunteers from the group age of 12-17 years and showed that the safety of CoronaVac, at that population, was high, with mild adverse effects in its majority (Level 1), being pain in the area of the injection the most frequent symptom related. The production of antibodies was evaluated in the saliva and serum collected from teenagers after 4 weeks of the vaccinal scheme (2 doses of the vaccine with a gap of 28 days). The results showed a significant production of igG anti-S1 antibodies in the saliva and neutralizing antibodies in the serum of teenagers from the group age of 12-17 years. The cellular immunity, evaluated by the presence by T cell productors of IFN-gamma in response to the peptides of the M, S and N proteins of the virus, also increased in this group of teenagers. The data presented until this moment indicates the safety and immunogenicity of the vaccine scheme with CoronaVac on teenagers.


Speech title: Analysis of the safety in the pediatric population and general population that received the booster dose of CoronaVac in China

The third speaker, doctor Jiayi Wang, manager of pharmacovigilance from Sinovac, presented data regarding the safety of CoronaVac on individuals from different group ages (3-17 years of age; 18-59 years of age and older than 60 years). The adverse effects were mild in its majority (Level 1 and 2) and, besides the pain in the area of the injection, they were not different from the placebo group.

Doctor Wang also presented safety data regarding the application of a third dose of CoronaVac, 8 months after the second dose, in adults from 18-58 years of age and olders than 60 years. The related adverse effects were mild (Level 1 and 2), without the occurrence of effects more severe.

According to doctor Wang, with the application of CoronaVac was not identified, until this moment (November of 2021), rare and serious adverse effects and risks of myocarditis/pericarditis and  thrombotic events such as Thrombosis with Thrombocytopenia Syndrome, that were already reported by vaccines based on adenovirus vectors and of mRNA (Information obtained from the Advisory Committee on Immunization Practices - ACIP, October of 2021).


Speech title: Immunogenicity of the CoronaVac vaccine on patients with autoimmune rheumatic disease (ARD)

The professor Eloisa Bonfá, full professor of Rheumatology, director of the Rheumatology Department and clinical director of the Clinical Hospital from the School Medicine of the University of São Paulo (USP), presented results of a clinical prospective study of phase IV to evaluate the safety and immunogenicity of CoronaVac on individuals with autoimmune rheumatic diseases. The presentation of doctor Bonfá has as an objective to comprehend the factor related to the low or moderate vaccine response of these patients that presented alterations at the immunological response, are susceptible to serious infections and may become carriers of new variants. The study, realized with 910 patients with different autoimmune rheumatic diseases, with or without immunosuppressors, showed that the response of IgG anti-S1/S2 antibodies and neutralizing antibodies increased on this patients, even though it was on minor intensity than on healthy controlled individuals of the same age group.

According to the data presented, the response of patients that were not exposed to SARS-CoV-2, after the immunization with two doses of CoronaVac, is minor than the response of patients that were previously exposed and from the healthy controlled group. This response, according to the presented data, promoted a significant reduction of incidence cases and hospitalizations related to Covid-19 in these patients, in a period of high cases associated with the Delta variant in São Paulo State.

Afterwards, the professor Bonfá presented data regarding the immunization with a third dose of CoronaVac in patients with autoimmune rheumatic disease. The study indicates that the third dose increases the titers of IgG anti-S1/S2 antibodies and of neutralizing antibodies on these individuals, even it being in a minor intensity than on individuals of the control group.

The study indicated that some of the immunosuppressant medicines and biological therapies used by the patients with rheumatic diseases are associated with the minor response of antibodies. Besides, the interruption from 1 to 2 weeks of the immunosuppressant medicines, did not aggravate the clinical evolution of the patients with low activity of the disease and promoted a higher antibody response.


Speech title: Safety and immunogenicity of CoronaVac on individuals with chronic diseases and the third dose on individuals with low response to the primary immunization

Doctor Zhijie Zhang, professor and main researcher of the Biology System Group in the State Laboratory of of Conservation and Utilization of Bioresources of Yunnan in China, presented results of retrospective study realized on China, regarding the safety and immunogenicity of the CoronaVac vaccines in carriers of chronic diseases such as arterial hypertension, coronary heart disease, chronic respiratory diseases, diabetes, obesity and cancer. The presented data showed that, in a general way, the response of these patients was at the same intensity of the control group. The safety of CoronaVac, according to the presented data, was equivalent in both groups.

Doctor Zhang presented an immunogenicity study of the third dose from CoronaVac on vaccinated individuals with adequate immune response and on individuals considered as non responders to  the immunization scheme of two doses. The third dose on this group of non responders induced a significant increase in the titers of neutralizing antibodies. Was also verified an increase in the response of specific T cells for the virus in this group of non responders.