A study carried out by researchers from Chinese universities and published last Monday (10) in the journal Emerging Microbes & Infections, points out that the CoronaVac vaccine, produced by the Butantan Institute and the Chinese laboratory Sinovac, is effective in neutralizing the Ômicron variant. The study is still preliminary.
Despite having already been published and peer-reviewed, the medical-scientific article contains data observed in the laboratory, which still does not demonstrate whether there is the same effectiveness in the general population.
For the study, the researchers used pseudoviruses containing the Spike protein from seven variants of the Sars-CoV-2 virus: Omicron, Alpha, Beta, Gamma, Delta, Lambda and Mu. A pseudovirus is a viral particle that has all the properties of a virus, except that it does not infect cells. Pseudoviruses were used in research because they allow safer manipulation in the laboratory.
In the experiment, blood plasma from people vaccinated with CoronaVac and also from people with previous infection was used. These samples are then infected with the pseudoviruses that carry the Spike protein of the variants.
The test consists of checking whether antibodies generated as a result of the vaccine will neutralize, that is, fight the virus in this culture. The result is then compared with the neutralizing capacity of antibodies of the virus lineage that circulated at the beginning of the pandemic.
Neutralization tests can assess the ability of antibodies to eradicate the virus, but do not measure other aspects of the body’s defense, such as the memory of the immune system.
What the study says After producing the pseudoviruses of the seven variants, researchers analyzed neutralizing antibodies from 16 people convalescent from covid-19 and also from 20 people who had taken two doses of the CoronaVac vaccine. The study did not include people who took booster shots.
In the case of people who had previous infection, a 10.5-fold reduction in neutralization against the Ômicron variant was observed, that is, neutralization by Ômicron is 10.5 times worse than for the original strain of the new coronavirus. In the case of Alfa, the reduction is 2.2 times; 5.4 times against Beta; 4.8 times against Gamma; 2.6 times against Delta; 1.9 times against Lambda; and 7.5-fold against the Mu variant.
In the test carried out with the neutralizing antibodies of the 20 people who had taken the two doses of the CoronaVac vaccine, the average neutralization reduction was 12.5 times over Ômicron; 2.9 times against Alfa; 5.5 times against Beta; 4.3 times against Gamma; 3.4 times against Delta; 3.2 times against Lambda; and 6.4-fold against the Mu variant.
For the authors of the work, this reduction of about 12.5 times of neutralization of CoronaVac against Omicron – which demonstrates loss of vaccine effectiveness in relation to the original strain – is much “better than the published works on two doses of vaccines”. of messenger RNA, in which a 22-fold and a 30- to 180-fold decrease in neutralization was observed in those immunized with Pfizer”.
Even so, the authors point out that comparing the CoronaVac studies with Pfizer can be problematic, as the difference found between them can be attributed to different trials or different samples.
“CoronaVac, or other inactivated vaccines, induce a larger repertoire of immunity against covid-19. Recently, there is scientific evidence that the ability of CoronaVac to neutralize the Omicron variant is greater than the ability of vaccines based on protein S. The consequence of this is that inactivated vaccines, such as CoronaVac, are more resistant to the variants”, he said. Dimas Covas, president of the Butantan Institute.
For experts who read the study published in the scientific journal, there is still a lack of data to be able to say that two doses of CoronaVac would be enough to neutralize Ômicron. They point out that there is a lack of data, for example, on cellular response. They also point out that the result observed with neutralizing antibodies does not always correspond to what is observed in real epidemiological scenarios.
All vaccines approved to date have been developed to fight only the original strain of SarS-CoV-2, which initially emerged in China. All of them show, to a greater or lesser degree, a decrease in effectiveness in relation to the variants.
Regardless of the outcome of this study, experts remember that vaccines save lives. Yesterday (12), in a press conference, the executive coordinator of the Coronavirus Contingency Center in São Paulo, João Gabbardo, said that the vaccines that are being applied around the world help prevent deaths and hospitalizations from covid-19.
According to him, the Ômicron variant, which caused Covid-19 cases to explode around the world, has been, in general, a pandemic of unvaccinated people. “We are facing a pandemic of the unvaccinated. And when we talk about the unvaccinated, we are talking about people over 18 years old who have not completed their vaccination schedule and children who have not yet been vaccinated. These two segments are responsible for this increase in the number of hospitalizations and cases”, he said. “When they say that this variant is harmless, that the cases are mild, we have to take into account that this is the result of vaccination. The number of people who are still infected is very high. And hospitalizations, although not so serious, are very high,” said Gabbardo.
Immune response – The Butantan Institute reported that another study, carried out in Chile and which has not yet been published, showed that three doses of CoronaVac were able to reinforce the cellular immune response against the Ômicron variant.
“The first results we got are cellular responses, which are cells called T lymphocytes, which recognize coronavirus antigens. We were able to measure the ability of recognition and immune response in samples obtained from people vaccinated with two doses of CoronaVac plus the booster dose, and we detected a significant level of recognition of the Omicron variant S protein,” said researcher Alexis Kalergis. , director of the Millennium Institute of Immunology and Immunotherapy, professor at the Pontifical Catholic University of Chile, in an interview with Rádio Pauta.
For the research, we analyzed a group of 24 people with a complete vaccination cycle made with CoronaVac and who had received a booster dose of the same immunizer after six months. Blood samples from vaccinates were evaluated in the laboratory to verify the specific ability of T lymphocytes to identify strains of the Omicron variant. “These T lymphocytes have the ability to recognize infected cells to eliminate them. To achieve this, the T lymphocytes must also produce an antiviral molecule called interferon gamma and our results show that this molecule was effectively produced”, said the Chilean researcher.