A study by the Oswaldo Cruz Foundation found the effectiveness of fortifying agents from AstraZeneca / Oxford E Coronavac in reducing hospitalizations or deaths in the elderly, including the gamma variant (P1), responsible for most cases of Covid-19 in Brazil.
Technical analysis evaluates both individuals who have been vaccinated with at least the first dose and those who have been vaccinated with two doses. In the first case, regardless of the Covid-19 vaccine applied, the efficacy was 73.7% for those aged 60 to 79, and 63% for people over 80.
With at least the first dose of AstraZeneca/Oxford, produced by Fiocruz in Brazil, an efficacy of 81.7% was found for those aged 60 to 79, and 62.8% for those over 80. With Coronavac, the observed rate was 70.3% for those between 60 and 79 years old, and 62.9% for those over 80.
With the complete two-dose regimen, the efficacy increases, regardless of the vaccine applied, to 79.8%, in those aged 60-79 years, and 70.3% over 80 years of age. With two doses of AstraZeneca, effectiveness has been estimated as 93.8% over 60 to 79 years, and 91.3% over 80 years. Among those vaccinated with two doses of CoronaVac, rates were 79.6% aged 60 to 79 years, and 68.8% over 80 years old. Efficacy decreases with age because the immune system in the elderly loses its ability to protect the body.
The effectiveness of these vaccines has previously been demonstrated in clinical studies. The technical note authors note that one difference of this study is that it provides evidence of vaccine efficacy against variants of concern, which have greater transmission and dominance in Brazilian territory, such as P1.
“There are very high values of infection rates at the end of February and the beginning of March, when the process of reducing the number of cases begins, and they are more expressive for age groups 60-79 years and 80 years and older,” says a note. “With the vaccination efficacy results described here and with greater vaccination coverage in these ranges compared to others in the period, vaccination was an important factor in reducing the number of serious cases and deaths.”
The study was conducted through statistical analysis using vaccination databases from the National Immunization Program. With data reported as of June 7, the assessment included total records of more than 40 million vaccinated with at least one dose of the vaccine and more than 798,000 acute cases or deaths, with severe acute respiratory syndrome with confirmed or suspected Covid-19. Immunized and non-immunized cases were differentiated, and then stratified by age groups.
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