Covid-19: Chinese vaccine safe and immune response in the first stages of trial

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The findings of the initial phase clinical trial, which were published today in the scientific journal “The Lancet Infectious Diseases”, also point to positive levels of tolerance for all doses tested, with no reports of serious adverse reactions among participants.

The first tests of BBIBP-CorV, a potential inactivated vaccine against covid-19 that is being developed in China, involved more than 600 healthy volunteers, between 18 and 80 years old, allowing to evaluate the effects also in a group of older people .

According to the results, antibody responses were detected in all volunteers 42 days after vaccination, encouraging news for researchers.

“Protecting older people is a key objective of a successful vaccine, as this age group is at an increased risk of serious illness. However, vaccines are sometimes less effective in these groups, because the immune system weakens with age, ”explained one of the authors, Xiaoming Yang.

Among participants over 60, the response was still slower, taking 42 days for antibodies to be detected in all participants in that age group, compared with the 28 days required for younger participants.

On the other hand, the two groups also showed differences in relation to the level of antibodies, which was higher in participants between 18 and 59 years old.

This study, however, was not designed to assess the vaccine’s effectiveness and, therefore, it has not yet been possible to conclude whether the induced immune response is sufficient to protect against infection by the new coronavirus.

In the first phase, the authors sought to find an ideal safe dose of the vaccine, based on the inactivated SARS-CoV-2 virus and an adjuvant.

In both groups, composed of 96 people, the vaccine was tested at three dosage levels, with two vaccinations on day 0 and 28. Another group of 48 people received a placebo.

The second phase, in turn, was designed to identify the ideal schedule for vaccination and only four hypotheses were tested: one dose or two doses at three intervals (between days 0 and 14; between days 0 and 21; and between days 0 and 28). A total of 336 participants received the vaccine and another 112 the placebo.

The highest antibody responses were induced by two doses of the vaccine on days 0 and 21 or 0 and 28.

“Our results indicate that a booster injection is needed to obtain the best antibody responses against SARS-CoV-2, which may be important for protection. This gives us useful information for a phase 3 trial, “said Xiaoming Yang.

Throughout the clinical trial, participants did not report any side effects and after the first and second vaccinations, laboratory tests were performed to assess the function of different organs.

According to the results, there were no adverse events recorded within 28 days after vaccination and the side effect reported most often was pain at the injection site.

The authors mention some limitations of the study, especially the duration of the follow-up (only 42 days) and the fact that children and adolescents were not included. These groups will only be included in clinical trials when analyzes of adult data are complete.

Currently, there are 42 potential vaccines against covid-19 undergoing clinical trials.

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