Chile’s ongoing COVID vaccination, primarily based on China’s Coronavac vaccine, has shown 56.5% efficacy against infections two weeks after injection of the second dose, but no significant effect after the first, according to a study released Tuesday.
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This study in real conditions, carried out by the University of Chile, took into account the overall effect of vaccination in this country where two vaccines have been administered since December 24: the Coronavac vaccine from the Chinese laboratory Sinovac which represents the overwhelming majority (93%) of the doses administered, and the German-American vaccine Pfizer-BioNTech.
To date, Chile, with a population of 19 million, has administered at least one dose of vaccine to 7.07 million people and two doses to 4.04 million, or more than 26% of the target population. countryside – 15.2 million inhabitants.
The Chilean study draws three conclusions about the effectiveness of this immunization: it is 56.5% two weeks after people have received the two doses; 27.7% for those who received both doses for less than two weeks; and barely 3% (equivalent to the margin of error) for those who received only one dose.
“Getting vaccinated very significantly reduces the possibility of contamination. This does not eliminate it, but it greatly reduces it ”, declared the rector of the University of Chile, Ennio Vivaldi, during the press conference presenting the results of this first study in real conditions.
Another lesson, according to Mr. 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 a person who has not been vaccinated,” he emphasizes.
Regarding new infections in people over 70, most of whom are already vaccinated in Chile: according to the study, among people aged 75 to 79, there would have been 80% more infections if the vaccine had not been administered. 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-life study involving 1.2 million people showed an efficacy of 94%.