What does the first real-life study say about the efficacy of the Chinese vaccine applied in Chile?

Chile is going through a severe wave of coronavirus, perhaps the worst since the declaration of the pandemic. According to official data from the Ministry of Health, high daily infections have been recorded in recent days and with a record of occupancy of intensive units, despite the fact that 45% of the population, 7 of the 19 million inhabitants, has received the least one dose of the vaccine.

The current situation has been above the peak of the first wave, recorded in June, and has increased exponentially. As many experts attempt to give an explanation, contrasting with the success of vaccination in Israel or the UK, the effectiveness of the Chinese vaccine applied in the country is starting to be questioned.

A recent study notes that the vaccination strategy in Chile is mainly based on the Chinese Coronavac vaccine from the Sinovac laboratory. From this data, the University of Chile conducted a real-life analysis of the outcome of the plan, which has administered two vaccines since December 24: Coronavac, which accounts for the overwhelming majority (93%) of the doses administered, and the German-American Pfizer-BioNTech.

Data associated with the work showed an Asian developmental efficacy of 56.5% against infections two weeks after the injection of the second dose, but no significant effect after the first, at only 3%.

To date, Chile, with a population of 19 million, has administered at least one dose of vaccine to just over seven million people and two doses to over 4 million, more than 26% of the total. target population, which reaches 15.2 million. inhabitants. The Chilean study draws three conclusions on the effectiveness of this vaccination: it is 56.5% two weeks after people have received both doses; 27.7% for those who received both doses for less than two weeks; and only 3% for those who received a single dose.

The effect of the plan

During the press conference which presented the results of this first study in real conditions, the rector of the University of Chile, Ennio Vivaldi, explained that “Vaccination greatly reduces the possibility of contamination. This does not eliminate it, but it reduces it a lot ”.

According to Vivaldi, “the first dose of vaccine has no significant effect after four weeks.” Six weeks after the administration of a dose, “we are in the same situation of vulnerability to infection as an unvaccinated person,” he said.

The work also analyzes new infections in people over 70, most of whom are already vaccinated in Chile, and points out that In people aged 75 to 79, there would have been 80% more infections if the vaccine had not been given. This percentage drops to 60% for people aged 70 to 74.

According to the authors, the efficacy of the Coronavac vaccine is 54%, in line with large-scale trials conducted in Brazil which have shown an overall efficacy rate of around 50%.

For Pfizer-BioNTech, the researchers relied on data provided by Israel, where a real-world study involving 1.2 million people showed 94% effectiveness.

More young people infected

As a result of vaccination, the age of people in intensive care beds has changed across the country. Today, according to official data, there are more hospitalized between 40 and 49 years old (469), than those over 70 years old (378).

The latter are slightly more numerous than the youngest (359 admitted before the age of 39). But mortality has not decreased and remains at 2.4%. What has happened in Chile is that COVID-19 has started searching for victims in other groups. Four weeks ago, for example, around 80% of those who died were over 70, but that number is declining.

The same academic investigation maintains that the vaccine from Chinese laboratory Sinovac has slowed the increase in new daily cases that Chile has experienced for two months by around 10%, and by up to 64% in those over 70.

“If the level of circulation of the virus is maintained, when the whole world is vaccinated, we will have 46% fewer infections,” said Dr Eduardo Engel, an academic at the University of Chile, one of the few institutions in have published a report on the effectiveness of this vaccine.

Towards a possible third dose?

A document from the Millennium Institute of Immunology and Immunotherapy (IMII) and the Catholic University of Chile, pointed out that the percentage of people who had antibodies after the second injection, and according to the data collected , suggest that the Sinovac vaccination process may need to be with more than two doses.

“This is something that needs to be evaluated and is expected to happen in some patients, not only the elderly, but also some immunocompromised,” said Nicolás Muena, vaccine expert and virologist at Science. and Life Foundation.

Lack of data

Meeting between March 22 and 25, the anti-Covid-19 vaccines from Chinese laboratories Sinopharm and Sinovac were reviewed by the Strategic Advisory Group of Experts (SAGE) on vaccination of the World Health Organization (WHO) , which confirmed its value. In a document summarizing the main points raised at the meeting, experts said that these two Chinese vaccines – which have submitted a request for approval to the WHO – have “demonstrated their safety and good efficacy against Covid-19 when the patient is showing symptoms. “.

However, the same experts pointed out the paucity of data. “But data is lacking (…) concerning the elderly and those suffering from other illnesses. They added: Once introduced, studies on the efficacy and safety of these two vaccines “will be needed to assess their effects in these subpopulations.” WHO decisions on registration applications submitted by Sinopharm and Sinovac are not expected until at least early April.

A vaccine imposed in Brazil

According to the latest update from the Ministry of Health, the vast majority of applied vaccines (82.2%) come from Coronavac, developed by the Chinese company Sinovac in association with the Butantan Institute and produced in Brazil since December. The remaining 17.8% comes from AstraZeneca-Oxford, which in Brazil is produced by the Oswaldo Cruz Foundation (Fiocruz).

Last year, Coronavac was at the center of an intense debate between President Jair Bolsonaro, who dismissed the immunizer promoted by Governor João Doria, the governor of São Paulo. More than two months after the start of the vaccination campaign in that country, Coronavac remains the only widely available vaccine, while the federally promoted Oxford vaccine is slowly entering. The country’s government, however, is negotiating to obtain the Russian “coup” Sputnik V and with the Indian company Bharat Biotech, which produces Covaxin.

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