For more than three years we have been “living” with the SARS-CoV-2 coronavirus on a daily basis and, in that period, many people have already been infected or are vaccinated. Faced with this new reality, Canadian scientists investigated the level of immunity that people who had covid-19 preserve after a year of disease control.
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Published in the scientific journal Lancet Infectious Diseases, the systematic review — an investigation that compares results obtained by other studies on the same topic — was led by researchers from the University of Toronto and the University of Calgary, both located in Canada.
Protection against severe forms of covid-19 is still good
According to the authors, most people with previous infection or hybrid immunity — who have been infected and are vaccinated — still have good protection against severe forms of covid-19. “All protective estimates declined in the months following reinfection, but remained high and sustained for hospital admission or severe illness,” the authors state.
Furthermore, the scientists point out that “individuals with hybrid immunity [vacina e infecção] had the greatest magnitude and durability of protection.” However, immune defenses decline for all over time, indicating the importance of regular booster doses.
What is the real level of immunity against covid-19 after a year?
People who were only infected with the covid-19 virus 12 months ago maintain a protection rate of 74.6% against severe forms of the disease. For milder forms of the disease, the protective capacity is much lower, estimated at 24.7%,
Now, considering hybrid immunity, the protection index is excellent for severe forms or hospitalizations, calculated at 97.4%. Analyzing the risk of symptomatic but mild forms of covid-19, protection is 41.8%.
To reach these conclusions, the researchers reviewed the results of 11 scientific studies that evaluated the level of immunity after infection with covid-19. In addition, another 15 studies that detailed cross-immunity protection were considered.
Source: Lancet Infectious Diseases