The decision of the Ministry of Health to apply a third dose of Covid-19 vaccines to elderly people over 70 years of age and immunosuppressed, starting on September 15, using preferably immunizers from Pfizer or AstraZeneca, is supported by the scientific community.
Contrary to what the São Paulo government says, the choice of RNA vaccines (such as Pfizer, based on innovative messenger RNA technology) or viral vector (such as AstraZeneca, which uses a harmless virus to instruct the body on how protect yourself from Covid) for the booster dose for the elderly and immunosuppressed was a technical and unanimous decision among the members of the Technical Advisory Board for immunization matters in the health portfolio.
The group is formed by representatives of scientific societies (such as the Brazilian Society of Infectology and the Brazilian Society of Immunizations), Conass (National Council of Health Secretaries) and Conasems (National Council of Municipal Health Secretaries), among others.
In São Paulo, however, the state governor, João Doria (PSDB), the state health secretary, Jean Gorinchteyn, the director of the Butantan Institute, Dimas Covas, and the executive coordinator of the scientific committee that advises the management, João Gabbardo , have advocated the use of any immunizing agent that is available at the time of booster dose application.
The application of an additional dose in people over 90 years old starts in São Paulo next Monday (6).
The argument, they say, is that Technical Note No. 27/2021, published on August 26, makes reference to two studies conducted by Sinovac, the Chinese manufacturer of Coronavac, which indicate an increase in the immune response after a third dose of the immunizing agent. in people up to 59 years and in those aged 60 years and over, between six to eight months after the second dose.
“At the time of completion she [Rosana Melo, a secretária de enfrentamento à Covid-19 do ministério que assina a nota] concludes for the vaccine from AstraZeneca and Pfizer. We are dealing here with technical, scientific issues and these point out that the third dose with Coronavac greatly increases the immune response. On the other hand, we have a position that is even more political by the Ministry of Health when it discredits (…) this vaccine as a third dose”, said Covas, last Wednesday (1˚) at a press conference at Palácio dos Bandeirantes.
However, the two studies cited by Covas, despite pointing to an increase in the rate of neutralizing antibodies in the body of three to five times, in the case of people aged 18 to 59 years, and up to seven times in those over 60 years, also indicate a significant drop in these antibodies six months after the application of the second dose in both groups.
The reduction in the protective capacity of vaccines has already been verified for all types of immunizing agents, but it is much more accentuated in vaccines with inactivated virus, as is the case with Coronavac. This is because the innovative messenger RNA or even viral vector technology induces a high immune response compared to traditional vaccines (inactivated virus ones), and, even with the decay, it remains high.
Furthermore, effectiveness — or real-life efficacy — studies conducted in Brazil indicate only 35% protection of Coronavac against deaths in people aged 90 years and over – in this sense, a third dose of the same immunizing agent would not be sufficient to provide the protective response needed in this age group, experts say.
Last Friday night (3), Anvisa reported that it met with Butantan and requested data from the institute to prove the efficacy and greater generation of immune response of the Coronavac booster dose, in addition to data that have not been presented so far. about the immunogenicity of the vaccine.
A heterologous booster scheme, that is, the combination of vaccines different from those used in the first doses, however, already has solid evidence of a considerable increase in the immune response, explains Julio Croda, infectologist and researcher at Fiocruz.
“There are two booster studies [dose de reforço] three weeks apart from the second dose, one with Coronavac/AstraZeneca [conduzido na Tailândia] and another with Coronavac/Pfizer [conduzido em Hong Kong]. The three-dose schedule of those who received Coronavac and then received the viral vector or RNA vaccine shows a ten to one hundred times greater response in terms of neutralizing antibodies. The two third-dose studies with Coronavac had between five and seven-fold increases in antibodies. The benefit is unmistakable [para o uso de vacinas de RNA ou vetor viral]”, he says.
Similarly, a study of nearly 800 people conducted in the UK evaluated the heterologous application (of different brand vaccines) of Pfizer with AstraZeneca and of AstraZeneca with Pfizer. “The mixture of these immunizing agents also generates a more robust immune response, without an increase in adverse effects”, explains Croda, which may also indicate that it is okay to apply a booster with Pfizer in the elderly who received AstraZeneca at the beginning of the year.
The previous justification for not choosing the vaccine brand, in an attempt to fight the so-called “sommeliers”, was the fear of not having immunizations of a certain type available for everyone, explains Ethel Maciel, an epidemiologist and professor at the Federal University of Espírito Santo.
“But now we have more knowledge of how vaccines work in each group, and it’s natural that we have to reformulate our thinking. This does not mean being against Coronavac, which was instrumental in the beginning, it saved millions of lives. If we didn’t have Coronavac a lot more people would have died. However, to say that a third dose of Coronavac is similar to a third dose of heterologous Pfizer, there is no evidence to support this”, he says.
For Renato Kfouri, director of Sbim (Brazilian Society of Immunizations) and member of the ministry’s technical advisory board, the decision of the SP government leaves the logic behind science and further confuses the population, who do not know who to trust.
“The important thing is that the campaign is unified. When the SP government says it will use any vaccine, it doesn’t help the campaign in general. The political dispute that the federal government has made so far is so bad [contra as vacinas] how much this dispute that São Paulo poses. This hinders communication”, reinforces Maciel.
The same thought is shared by immunologist Cristina Bonorino. “Use the dose that is currently available [da dose adicional] in the elderly and the immunosuppressed, it is to fall into a terrain of ‘let’s do anything’, without a logical argument”, he says.
Bonorino, who advocates a complete revaccination scheme in the elderly, with two doses of Pfizer, and not just an additional dose, since the 95% efficacy found in clinical trials of the immunizing agent is only offered with the complete scheme, recalls that the Ministry is conducting four separate booster dose studies. Research looks at booster with Pfizer, booster with AstraZeneca in the old version, booster with an updated version of AstraZeneca and booster in individuals who took Coronavac with one of four options (Pfizer, AstraZeneca, Janssen or Coronavac).
“If the Ministry itself recommended Coronavac as a backup, it would be going against the very studies it is funding. It’s like taking and throwing money away if you don’t follow what the evidence says,” he says.
By defending Coronavac as an alternative to the third dose, the government of SP is also supported by the argument of a possible lack of doses to complete the vaccination schedule for adults over 18 years old who received the first dose of AstraZeneca or Pfizer and also on the need not to interrupt the vaccination of adolescents — whose only vaccine authorized for use is that of Pfizer.
“The federal ministry has already placed in that same technical note the anticipation of the second dose of AstraZeneca and Pfizer in adults for eight weeks, so the ministry’s assessment is that it is possible to boost elderly and immunosuppressed patients and, at the same time, advance full vaccination . For the quantity of doses, it is possible to do both”, explains Maciel.