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The Covid-19 vaccine from Chinese manufacturer Sinovac is safe and has the ability to produce an immune response in the body 28 days after its application in 97% of cases, according to a peer-reviewed article published in the journal on Tuesday. (17). Infectious Diseases Lancet.
The results are the result of an analysis of phase 1 and 2 clinical trials conducted in China in April and May with 744 healthy volunteers aged 18 to 59 years with no history of infection with the Sars-CoV-2 coronavirus.
Although the Coronavac vaccine is already in phase 3 testing (the last one before approval) in humans in several countries, including Brazil, where the immunizer is being tested in partnership with the Butantan Institute, it is the first official publication of the tests. of the previous phases. All other phase 3 vaccines had already published their phase 1 and 2 results.
Last week, pharmaceutical companies Pfizer and Moderna released preliminary and more advanced phase 3 results based on interim data analysis. Both were more than 90% effective, but the details have yet to be published in a scientific journal.
The randomized, double-blind and controlled study (considered the gold standard because it randomly divides the participants into groups, without knowing if they are taking the vaccine or a placebo, to avoid bias) has shown good results, with the production of antibodies already verified after 14 days, with a production peak at 28 days.
144 people were evaluated in phase 1 and another 600 people in phase 2, totaling 744 volunteers, of which 743 received the vaccine or placebo (one volunteer dropped out during the study).
The good news is that the vaccine induced the production of neutralizing antibodies, whose function is precisely to prevent the virus from entering cells, which suggests that the vaccine may be effective in preventing infection and not just the development of the disease. However, T lymphocytes, responsible for ensuring cell protection, were not analyzed.
In phase 1, the individuals were randomly assigned to two groups. The first group received the lowest dose of the vaccine and, after seven days, the volunteers in the second group received the highest dose. A booster dose was applied to each group after 14 days.
In phase 2, the 600 participants were randomly divided into three groups. The first and second received the lowest and highest dose of the immunizer, respectively, and the third, placebo.
Seroconversion, that is, the presence of specific antibodies in the blood against the coronavirus, was already identified 14 days after the first dose in phase 1, but only in half (12 out of 24) of the individuals who received the vaccine from high dose and in 45.8% (11 of 24) of people who were immunized with the lowest dose. After 28 days, that rate increased to 83% (20 of 24). Neutralizing antibodies were not detected in the subjects who received the placebo.
In the 600 phase 2 participants, seroconversion was identified in 92.4% (109 of 118) of individuals after 14 days of immunization with the lowest dose and in 98.3% (117 of 119) of those who received the lowest dose. discharge 14 days later. After 14 days, when the second dose was applied, the seroconversion identified was 94.1% (111 of 118) in the individuals with the lowest dose and 99.2% (117 of 118) in those who received the lowest dose. more powerful injection.
As both vaccines induced an immune response, the researchers say there is not a significant difference in the dose to produce neutralizing antibodies, but in the time of administration. The two-dose schedule with an interval of 28 days between them was the best way to achieve a high antibody rate in the blood more quickly.
However, the authors affirm that, given the emergency situation of the pandemic, in an interval of 14 days between doses it is already possible to detect antibodies in the blood, and this may be an option to immunize the population more quickly.
Reported adverse effects were mild, the most common of which was pain at the injection site (reported by approximately 35% of participants in each group). There were no serious side effects that could indicate a possible lack of safety of the vaccine.
Regarding the different doses, both were well tolerated, with few significant differences. The authors state that, unlike other vaccines whose vaccine platforms are non-replicating viral vectors (such as adenoviruses, the technology used in the Oxford / AstraZeneca, Johnson & Johnson and Sputnik V vaccines) and genetic (such as those from Pfizer and Moderna ), fever was not a common adverse effect of Coronavac.
The Sinovac pharmaceutical company vaccine is made from inactivated viruses. The idea is to modify the Sars-CoV-2 coronavirus by making it non-infectious.
Until phase 1, scientists used culturing Vero cells, cell lines commonly used in microbiological cultures, synthesized from cells isolated from the kidneys of a monkey species in the 1960s and used today, to multiply Sars. . CoV-2 in the laboratory.
However, after phase 2, the company began using bioreactors, a kind of industrial “cell factory” that uses heat, raw materials (cells or parts of them) and movement to produce infected cells on a large scale. The virus is then inactivated and incorporated into the vaccine.
Total inactivated virus vaccine production is similar to that used for rabies vaccine production. However, this type of vaccine needs significant safety tests. Phase 3 that is underway in Brazil should continue for at least six months.
In this third stage, some important questions must be addressed, such as the duration of protection against the virus, whether the immunizer is capable of preventing infection or simply protecting against the more serious disease, and whether the vaccine induces the immune response of the cells. T. answered.
The company has also started a clinical study in people over the age of 60, and the preliminary results of this study, published in early September, point to an immune response in this group, although less than that seen in individuals aged between 18 and 59 years. The vaccine was also shown to be safe in this age group.
There is still no approved vaccine for use in the population that fights Covid-19. Dozens of immunizers are being tested in humans, coming from different countries and using different technologies.
