Vaccination with booster doses to prevent coronavirus infections in Chile reaches percentages of effectiveness that range between 80% and 93%, while to avoid hospitalizations they are between 87% and 96%, according to a study by the Ministry of Health disclosed Thursday. The vaccines used for this purpose are the Chinese Sinovac, the American Pfizer and the British AstraZeneca.
Dr. Rafael Araos, advisor to the Undersecretariat of Public Health, said that the effectiveness of the Sinovac vaccine used as a booster to prevent infections rose from 56% to 80%; with Pfizer it rose from 56% to 90% and with AstraZeneca from 56% to 93%. To prevent hospitalizations, it rose from 84% to 88% with the Chinese, from 84% to 87% with the American and from 84% to 96% with the British, the study details.
AstraZeneca was used in Chile in the high-risk population, Pfizer in those under 55 years of age and Sinovac in those over 55 and in pre-adolescents.
Araos emphasized that the percentages between the three vaccines should not be compared, among other things because the percentages of the vaccines used for the first two doses vary a lot and also because “probably the risk of infection is now much lower than those vaccinated in March, when the country faced the second wave of the pandemic ”.
Authorities said this is the first study in the world to report the results of the use of booster doses, with various immunizers, in people who completed the inactivated virus vaccination schedule.
Araos explained that “there are no reports of real life studies using inactivated vaccines” to generate immune responses in the body, such as Sinovac. Chile, like other low- and middle-income countries, use them because they are also cheaper. Pfizer uses fragments of genetic material – messenger RNA – to elicit an immune response, while AstraZeneca contains a viral version of another virus to trigger antibodies.
The study includes 11.2 million people who received the two doses required by Sinovac as their primary regimen.
Later, the studies on the effectiveness of the reinforcement to prevent the arrival at the Intensive Care Units and the deaths will be disseminated, said Araos. He added that “the data looks very good.”
The South American country began on August 11 the reinforcement of vaccines in those over 55 years of age who had the two doses of Sinovac and, by age group, were inoculated with Pfizer, AstraZeneca and Sinovac. In September, the reinforcement of those under 55 years of age began. On Thursday, people between 28 and 35 years old were vaccinated.
In Chile, 88.8% of the target population, 15.2 of the 19 million Chileans, completed the vaccination schedule and 91% received the first dose. At the end of September, the process began with minors from 6 to 11 years old and to date 3.6 million have the reinforcement. The vast majority received Sinovac.
The country has reported 1.6 million infected and more than 37,500 deaths from COVID-19.
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