In Brazil, the application of the third dose of the vaccine began in September in elderly and immunosuppressed patients. Recently, the audience was expanded to all people over 18 years of age, and the interval between applications was reduced to five months.
People who have taken Coronavac can be immunized with Pfizer, Janssen or AstraZeneca in the booster. For those who received Pfizer, the booster dose could be either AstraZeneca or Janssen. Anyone who has taken AstraZeneca can be immunized with Pfizer in the booster. In the case of those vaccinated with Janssen, a second dose of the same immunizer will be needed and, after five months, a third dose of Pfizer.
Why is it necessary to apply the third dose?
The application of a booster dose has been advocated by specialists in view of the rise in infections among those immunized with the two doses. There is also scientific evidence that the protection induced by vaccines decreases over time, which puts, in particular, the most vulnerable groups at risk. The advance of the Delta variant — more transmissible — has also put authorities on alert.
Which groups are getting the third dose?
At first, only elderly people over 60 years old, immunosuppressed and health professionals received the booster with the third dose. On November 16, however, the Minister of Health, Marcelo Queiroga, announced that the government will expand immunization with an additional dose, covering the entire population over 18 years of age. The intention of the Ministry is to apply the boost to 103 million people until May 2022.
What vaccines are being used?
The Ministry of Health said there is a preference for the Pfizer vaccine, but Janssen or AstraZeneca vaccines can also be used. It should also be privileged, according to the Ministry, heterologous immunization, which is done with an immunizing agent different from the one applied in the first doses.
In addition to paying attention to changes in the vaccination schedule, one of the factors that proves the effectiveness of immunization agents is the way in which doses are conserved and stored. The ideal temperature conditions are in the temperature range between 2ºC and 8ºC in order to maintain the integrity and immunizing characteristics of the vaccines. Such conditions are possible with the use of scientific conservation chambers, equipment registered with the Ministry of Health/ANVISA, which meet all technological and legal requirements for the correct storage of doses.