Why WHO’s recent CoronaVac vaccine approval will be crucial in curbing the pandemic

The World Health Organization (WHO) has approved Coronavac for emergency use, after detecting that 51% effectiveness in preventing COVID-19 in advanced stage trials, and researchers say this will be the key to curbing the pandemic.

This general protection is lower than that provided by the other seven vaccines already listed by the WHO, but tests suggest that the inactivated virus produced by the Beijing company Sinovac, it is 100% effective in preventing serious illness and death.

“The CoronaVac will contribute significantly to the global fight against COVID-19 as a safe and moderately effective vaccine against SARS-CoV-2,” said Murat Akova., a clinical researcher in infectious diseases at Hacettepe University in Ankara, who researched this product.

CoronaVac approval on June 1 came about a month after the WHO approve another chinese vaccine, made in Beijing by state-owned company Sinopharm, which has been shown to be 79% effective against symptomatic disease. Both vaccines are already widely used around the world and are the source of China’s massive national vaccination campaign.

CoronaVac runs vaccination campaigns in more than 40 countries, including Chile and Botswana. Worldwide, more than 600 million doses have been administered. The Sinopharm vaccine has been approved in many other countries. But the emergency WHO approval could facilitate the distribution of both vaccines in low-income countries, through the COVID-19 Global Vaccine Access Initiative (COVAX).

The WHO’s efficacy estimate of 51% was based on data from late-stage trials among healthcare workers in Brazil, published online as a pre-print in April. Of the 9,823 participants included in the analysis, 253 had COVID-19: 85 in the vaccinated group and 168 in those who received the placebo. None of the vaccinated volunteers were hospitalized or died from COVID-19. Smaller and late-stage trials in Indonesia and Turkey have shown up to 84% higher efficacy.

The preliminary results of A post-trial study of 2.5 million people in Chile estimated that CoronaVac was 67% effective in preventing COVID-19 and 80% effective in preventing deaths from the disease, despite the presence of the Alpha (B.1.1.7) and Gamma (P.1) variants of the SARS-CoV-2 virus.

Preliminary results detailed at a press conference in Brazil suggest CoronaVac could make a significant dent in the pandemic. The Butantan Institute in São Paulo conducted the study, in which almost the entire adult population of Serrana was vaccinated with CoronaVac, found that its application significantly reduced COVID-19 cases, hospitalizations and deaths.

The fact that this vaccine can protect an entire city, despite the fact that nearly 40% of the population travel daily to areas where the pandemic was raging, it is “remarkable proof that this vaccine could be a game-changer in the control of the pandemic”, explained the leader of the trial. Ricardo Palacios, medical director of clinical research at the Butantan Institute.

The two approved Chinese vaccines use established technology based on inactivated viruses and can be stored at ordinary refrigerator temperatures. which makes them easy to distribute in resource-poor settings, but this type of vaccine appears to offer less protection against disease than mRNA.

“The researchers say it could be due to the technology itself. The vaccines use a killed version of SARS-CoV-2 to trick the human body into making antibodies against many regions of the virus. But only some of these antibodies are effective in deactivating the virus, ”he says. Gagandeep Kang, virologist at Christian Medical College, Vellore, India, who also advises WHO on immunization.

Other platforms induce more specific responses against specific parts of the virus, which is why they are more effective. MRNA vaccines encode the spike protein that SARS-CoV-2 uses to enter cells, triggering a large number of antibodies that block this protein.

Most COVID-19 vaccines are given in two doses and studies are underway to assess whether people will need to be boosted after that. These data could be particularly relevant for those who receive inactivated virus vaccines such as CoronaVac and Sinopharm injection, as they produce fewer antibodies, scientists say. “But the priority for now should be to vaccinate as many people as possible with their first two doses,” Kang added.

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