Oswaldo Cruz Foundation (Fiocruz)
The first edition of the bulletin on the COVID-19 vaccines' effectiveness in the Brazilian population, from Fiocruz's Vigivac project, was published on Thursday (12/9). The report, which presents analyses of the four vaccines administered in Brazil from January to October 2021, points out that all of them confer a great reduction in the risk of infection, hospitalizations, and death from COVID-19. Considering serious outcomes (hospitalization or death) in individuals aged 20-80 years, protection ranged from 83% to 99% for all immunizers. In the population under 60, all vaccines showed protection above 85% against the risk of hospitalization and above 89% for risk of death.
(Image: Courtesy House of Representatives)
Check the full bulletin (in Portuguese), with the description of the results found for each vaccine, the research methods used in the project, and the analysis of the epidemic context and coronavirus variants evolution in the regions of Brazil. The analyses of the project, coordinated by researcher Manoel Barral, from Fiocruz Bahia, were performed with anonymized individual information from the databases of the National Vaccination Campaign against Covid-19 (Covid-19 Vaccination), Influenza Syndromes Notifications (e-SUS Notifica), and Severe Acute Respiratory Syndromes Notifications (SARS 2020 and 2021; SIVEP-Gripe). These databases and their dictionaries are available on the SUS Informatics Department website (DataSUS).
Coronavac showed high effectiveness for the population aged 18 to 59 years, ranging from 89% to 95% and from 85% to 91% for deaths and hospitalizations, respectively. However, there was a significant drop in effectiveness in people aged 60 years and older. In the 60-69 age group, protection against severe forms of the disease was 81%, and was as low as 64% in the 80+ age group.
The researchers say that this reduction in protection in the elderly can be explained by several factors, but mainly by the longer follow-up time, long time since the last vaccination, and the greater vulnerability of the group that received the immunization, since Coronavac was the most used among the elderly and priority professionals, such as health and security personnel, who are more exposed to infection. In addition, the vaccine was administered during a period of higher virus circulation.
AstraZeneca was the most widely used vaccine in the country, according to the bulletin. The results for the adult population aged up to 59 years showed a 99% effectiveness of the immunizer against deaths. The drop in effectiveness also followed the increase in age group. In the group of people between 60 and 69 years old, the protection against infection was 89%, reaching 82% in individuals over 80 years old. With regard to deaths, people over 80 had 91% protection, slightly lower than the other age groups 60 to 69 and 70 to 79, which had 97% and 93%, respectively.
Analyses for the adult population up to age 59 who received Pfizer showed that protection remained above 96%. Protection against death and hospitalization from COVID-19 in this group was 99%. The researchers point out that Pfizer was administered to the youngest population and at an epidemic moment with lower virus circulation, which may favor the effectiveness of the vaccine.
In the adult population aged up to 59 years who received Janssen, the analyses showed protection against death of 78% to 94%. Protection against hospitalization was between 88% and 91%, and against infection, the effectiveness was between 68% and 73%. For the elderly population, it was possible to safely calculate the effectiveness only for the population aged 80 years and older, which had protection against death of 91% and against hospitalization of 93%.