CoronaVac jab less effective against the Gamma variant: study

The Chinese CoronaVac jab, a key tool in Brazil’s fight against COVID-19, is less effective against the Gamma variant first detected in the virus-ravaged South American country, according to a study.

The researchers found that the antibodies generated by the vaccine work less well against the variant than a previous coronavirus strain, while Gamma may also be able to reinfect people who had previously had the vaccine. virus.

Gamma’s ability to evade them immune system responses even in immunized people suggest that “the virus can potentially circulate in vaccinated people, even in areas with high vaccination rates,” the study’s authors said in a press release.

In the small study, researchers at the University of Campinas, Brazil, exposed both Gamma and a previous strain of the virus to antibodies in blood plasma of 53 people vaccinated and 21 people who had previously been infected with the virus.

In the vaccinated group, 18 people had received only one dose of CoronaVac – one of the main vaccines in Brazil’s coronavirus response – while 20 had recently received a second shot and another 15 had been vaccinated as part of the trial. Sinovac Clinic in August 2020.

They found that Gamma was able to escape the antibodies of almost all participants who had only received one dose, as well as those vaccinated in 2020.

Antibodies from the most recently vaccinated were effective, but less so than against the previous strain of the virus.

The study, published in The Microbe Lancet, also found that antibodies produced by previous infections had to be nine times higher to prevent gamma infection than to prevent diseases of the previous strain.

The authors said that these results make it possible to reinfect people who have already survived a case of COVID-19.

But they said since then clinical trials suggest that the vaccine is effective in prevention serious illness and death, it could be that the immune response it is more complex.

Each dose counts

CoronaVac was approved by the World Health Organization for emergency use in June.

At the time, the WHO said it was 51% effective against symptomatic diseases and 100% effective against hospitalization.

But the results of CoronaVac’s Phase 3 trials in Turkey – which did not take variants into account – were published on Friday in The Lancet two doses of the vaccine were found to have an efficacy of 83.5 percent in protection against symptomatic infections.

The vaccine was also found to be 100% effective against hospitalization.

The study included 6,559 participants who received the vaccine and 3,470 who were given a placebo.

All were adults between the ages of 18 and 59 and were given a 14-day dose difference.

The authors said the limitations of the trial include that participants were under 60 and at low risk, and called for more research to test efficacy among adults over and under 18, as well as against new variants. .

“The world needs every possible dose of anything safe and effective vaccine against SARS-CoV-2, ”they said.

Both papers will be presented at this year’s European Congress of Clinical Microbiology and Infectious Diseases.

© 2021 AFP