Reinforcement with a bivalent vaccine against Covid may be restricted to risk groups

The CTAI (Technical Advisory Chamber on Immunizations) recommended to the Ministry of Health last Wednesday (30) that the bivalent vaccines against Covid-19 be used as a booster dose only in higher risk groups, such as the elderly, immunosuppressed and pregnant women. For other audiences, such as young people without comorbidities, there is a lack of evidence on the advantages that a new booster would bring in avoiding the severity of the disease.

Similarly, this is the recommendation given to the health coordination of the transition of the elected government Luiz Inácio Lula da Silva (PT). Arthur Chioro, former Minister of Health and member of the coordination, says that an important focus in the transition is to regulate the vaccination scheme already recommended for the population —for the time being, the possibility of a fifth dose for non-priority groups is not discussed.

The folder headed by Marcelo Queiroga announced last Friday (25) that doses of the bivalent vaccine produced by Pfizer should arrive in Brazil this month. On the 22nd of last month, the drug received emergency approval from Anvisa (National Health Surveillance Agency) to be used in people over 12 years old.

Immunizers are composed of the original strain of Sars-CoV-2 and also of omicron subvariants. There are two templates: one contains BA.1 and the other contains BA.4 and BA.5. Due to this composition, they are an effective way against the forms of the virus with the greatest circulation in Brazil.

The number of doses of this delivery was not informed to the Sheet neither by the ministry nor by the pharmaceutical company.

The ministry’s current orientation is that, in people over 40 years old, two booster doses are applied – making a total of four doses for the Pfizer, Astrazeneca and Coronavac vaccines and three in the case of Janssen.

The recommendations given by the CTAI come as the ministry plans what to do with the new vaccines. The orientation of directing them to more vulnerable audiences as a new reinforcement is not a definition, since the chamber has no decision-making function. But, normally, the ministry follows what the group recommends.

The expectation is that, in the coming days, the folder headed by Queiroga will release a technical report updating the vaccination schedule against Covid-19. If the alterations really occur, a fifth dose (or fourth, for those who took Janssen) with the bivalent immunizer can be administered for higher risk groups.

THE Sheet asked the ministry if it intends to follow CTAI’s direction, but, until the publication of this report, there was no answer.

Younger

The CTAI recommendation leaves out younger people without comorbidity from the target audience of updated vaccines. According to Renato Kfouri, director of the Brazilian Society of Immunizations (SBIM) and member of the CTAI, the reason for this is that there is a lack of evidence of the real need to revaccinate younger people with the new model. “We don’t have evidence of loss of protection for severe forms in young people,” he says.

Even so, Kfouri points out that, in the future, the epidemiological scenario may change and then another booster dose will also be necessary for this public. “If we understand that even healthy young people without risk factors have an increased risk of hospitalization and serious forms, perhaps it would be the strategy to vaccinate everyone again.”

The position is reiterated by Chioro, from Lula’s transition. He also received expert advice and reaffirms that the bivalent vaccine, at least with current data, will not be indicated for young people in the report delivered to the future Minister of Health. “The bivalent would have a space for more vulnerable groups”, he summarizes.

For audiences with lower chances of developing serious conditions, the effort will be to increase the vaccination coverage rate for those who have not yet taken doses with monovalent drugs. “What became clear is that it is no use just buying a vaccine, because today there are [imunizantes] and people are not taking it. It has absurdly reduced the population’s adherence”, says Chioro.

Data from the consortium of press vehicles indicate that, by September, 48.4% of Brazilians had already taken at least one booster dose. Regarding two doses or one application of Janssen, there were about 80% of the population.

Among children, the numbers are smaller: among those aged 3 to 11 years, only 36% are completely immunized with two doses. “It’s no use making a booster with the bivalent if you don’t vaccinate the children”, summarizes Chioro.

In other countries

Updated vaccines are already adopted in countries that seek to control the spread of new variants of Sars-CoV-2 and avoid severe cases of Covid-19.

In the case of the United States, the CDC (Center for Disease Control of the USA) recommends doses of bivalent vaccines for adults and adolescents since September. The nomination also became for children in October.

Recently, the agency developed a clinical study whose results were published last Tuesday (22). In the research, handling a dose of bivalent immunizers resulted in additional protection to avoid symptomatic cases in people who had taken two, three or four applications of the original models.

Protection grows the longer the period of months in which the person took the last dose of the original vaccine. In subjects aged 50 to 64 years, boosting with an updated vaccine led to a 31% improvement in relative effectiveness two to three months after the last monovalent dose.

If the application of the bivalent immunizer was carried out eight months after the last dose of a drug composed only with the original strain of Sars-CoV-2, the improvement in effectiveness was 48%.

In Australia, the Australian Technical Advisory Group on Immunizations (Atagi) recommends both Pfizer and Moderna’s bivalent vaccines for people aged 18 and over.

Authorization for the use of Pfizer’s immunizer, however, is recent. According to Reuters, the country is expected to receive 4.7 million doses of the pharmaceutical and start applying the drug as a booster on the 12th.

In Latin America, Chile has also authorized the application of reinforcement for both Pfizer and Moderna. Unlike what happened in the United States and Australia, the country opted to follow a method of making new reinforcements available to higher-risk publics, following a model closer to that proposed to the Brazilian Ministry of Health.

Initially, only health professionals and immunosuppressed people over 12 years old were authorized for the drug. But, over time, Chile has increased the public and now people over 60 are part of this vaccination group.