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Duration of immunity and third dose of vaccines from inactivated viruses in the discussions of the second day of the CoronaVac Symposium

Publicado em: 01/01/1970

CoronaVac is one of the vaccines most safe and effective against SARS-CoV-2, being capable to maintain the immunity by several months after the second dose, what was pointed out by a diversity of researches that evaluated the humoral and cellular response of the vaccinated and were presented this Wednesday (8), during the discussions on the second day of the CoronaVac Symposium, an international event promoted by Butantan in partnership with Sinovac.

To initiate the morning discussion, the scientist Xiangxi Wang, main researcher from the Infection and Immunity Lab of the Biophysics Institute from the Chinese Academy of Sciences accentuated that the booster dose of CoronaVac fights the original strain of SARS-CoV-2 and its variants as well, including the Omicron. About four weeks after the application of the booster dose, there was a multiplication on the level of neutralizing antibodies against the Protein S, responsible for the entrance of the SARS-CoV-2 into the human cells. Besides, the booster dose increases the protection against new strains, elevating 17 times the level of neutralizing antibodies against the variant delta and the original strain from Wuhan, in 18 times against the variant alfa, in 19 times against the beta and in 14 times against the gamma.

The protection of the individuals immunized with CoronaVac against the variants gamma, beta and delta was also revealed, in Brazil, by the analysis of the neutralizing antibodies, realized by Edison Durigon, from the Department of Microbiology of the Biomedical Science Institute of São Paulo University (ICB-USP). In the study, the protection of the vaccinated was held high until five months after the second dose. For Durigon, the Covid-19 will be defeated if, during the next few years, the immunizing becomes updated with the variants in circulation. “I agree with using the current strain, but it needs to be updated to cover the variants that we are most worried about'', he said.

The specialist highlighted that the pandemics researches advanced a lot in Brazil during the last year because of the previous experience of the scientist  and because of the good relationship with the other Institutes, which was conquered during the studies of other epidemic studies such as SARS-CoV-1, Avian Influenza, H1N1 and Zika Virus.

The researcher of the Pontifical Catholical University from Chile, Alexis Kalergis, post doctoral in immunology and director of the Millennium Institute of Immunology and Immunotherapy, also pointed to similar results about the duration of the immunity. Kalergis punctuated that individuals that had both doses of the vaccine presented high taxes of seropositivity with neutralizing antibodies against the variants: above 97% for the original strain, over 80% for the variants alpha and gamma, over 75% for the delta variant and over 60% for the beta, according to his last studies.

The specialist in pediatric infectious diseases Ahmet Soysal, from the Pediatric Clinic of the Atasehir Memorial Hospital, in Turkey, compared the immunogenicity and the reactogenicity (the capacity of the vaccine to generate adverse or collateral reaction on the organism) of the inactivated vaccine on 103 professionals of the health system infected by SARS-CoV-2 in a light response or with no symptoms, and 627 professionals that did not contract the disease. CoronaVac induced a bigger production of antibodies on individuals that were previously infected.

The researcher Zhijie An, from the Control Center of Disease Prevention from China emphasized the vaccination progress with the contention of cases, presenting data of efficacy in the real world against delta and other variants. He highlighted that among the individuals vaccinated with both doses, the immunity decreased after six months, but after just two weeks of the booster dose the tendency was of an increase of 20 times in the immunity With one year of vaccination campaigns, 2,5 billion doses were applied in the Chinese population, immunizing 85% of the country. To monitor the immunogenicity and safety of the vaccines and possible outbreaks, the Chinese researchers used an extensive database of the immunized individuals, using smartphones as auxiliars for the registration.


The future of the vaccine

According to the researchers that participated in the sessions on the second day of the symposium, the greatest challenge for the next few years will be knowing the exact amount of time of the immunization and how many doses will be needed annually. The professor Yiming Shao, chief of the AIDS departament of the Control Center and Disease Prevention on China and vice-president of the Chinese Society of Microbiology, evaluates that will be necessary global collaboration to achieve effective solutions for all the continents. Shao does not discard the creation of other kinds of immunization in the future. “We need to make intelligent use of all the available vaccines to accelerate immunization on all continents. There are still a few places where less than 10% of the population have access to immunization”, he said. “In the future, maybe we can have different types of vaccines combined even oral medicine”

The CoronaVac Symposium will be held until Thursday (9), from 08 AM to 11 AM. The international online event counts with the presence of Brazilian researchers and from Chile, Turkey, China, Spain and the United States. The Symposium opening, on the first day, was realized by the President of Butantan Institute, Dimas Covas, and by the Sinovac President, Weidong Yi.

For the mediator and director of the Multipurpose Lab from Butantan Institute, Renato Astray, the importance of the Symposium has something to do with the quantity of foreign researchers together. “We can see data about the efficacy, about protecting the population or not, percentages, technical data about the quantity of antibodies generated, how is the cellular response, the profile of the memory cells. It was really interesting to see all this data being explained by diverses research groups”, affirms.

The scientific leader from Butantan, Denise Tambourgi, highlights the way that immunogenicity and antibodies neutralization were presented in studies made by different countries. “It brought a lot of information of how effective the vaccination is and the production of neutralizing antibodies against the variants in circulation. It called attention to a speaker in particular from China, about the repertoire of antibodies that CoronaVac can elicit in terms of the third dose during the immune response”, said the specialist. “Different discussion to enrich our knowledge and capacity of having a higher criticism of what we will do for the future.”