The four vaccines against Covid-19 applied in Brazil offer a high degree of additional protection against symptomatic infection and severe forms of the disease in people who have already contracted Sars-CoV-2. This is what a study led by researchers at the Oswaldo Cruz Foundation (Fiocruz), Julio Croda and Manoel Barral-Neto.
Research shows that the four vaccines are 39% to 65% effective in preventing symptomatic forms of the disease. In the case of the three vaccines with a two-dose schedule – Coronavac, AstraZeneca and Pfizer -, according to the scientists, the second dose provides much greater effectiveness when compared to the first and the average protection against hospitalization or death exceeds 80%, 14 days after the full vaccination course – compared to infected and unvaccinated people.
According to the study, it would be: 90.8% with AstraZeneca, 87.7% with Pfizer, and 82.2% with CoronaVac. At Janssen, of just one dose, it was around 59.2%.
Also according to the research, published on the Medrxiv website, this Wednesday (29), in the case of initial infection, the effectiveness against a symptomatic reinfection 14 days after the complete vaccination schedule is 63.7% for Pfizer, 53.4% for AstraZeneca, and 37.5% for CoronaVac, compared to coronavirus-infected and unvaccinated people.
Researcher Júlio Croda, from FioCruz Mato Grosso do Sul, explains that the main message of the study is the importance of being vaccinated.
“We see that some countries even recommend only one dose for those who had Covid, considering that they already have a certain level of neutralizing antibodies. But this kind of real-life assessment of effectiveness shows that there is an additional gain with the second dose. It is a substantial gain against severe forms”.
The survey was carried out from the national database on notification, hospitalization and vaccination against the disease. 22,565 people over 18 years old who had two positive RT-PCR tests were evaluated, and 68,000 who had a positive test and then negative, between February and November of this year.
“For AstraZeneca and Pfizer, there was only one article on serious outcomes, and it involved only 75 individuals. There was nothing on Janssen and CoronaVac for symptomatic disease and severe cases”, points out Croda.
hybrid immunization
Sars-CoV-2 infection induces robust immune-related T and B cell responses. The emergence of new, more transmissible variants, capable of escaping the immune system and resulting in new waves of infection and reinfection, renewed discussions on the subject.
According to the study, the combination of infections and vaccines could explain why Brazil, despite having a vaccine coverage comparable to that of the United States and European countries, has not observed a similar increase in hospitalizations and deaths during the period in which the variant Delta has become prevalent.
Reference: CNN Brasil
