It was tested in Argentina, has a high efficacy and has already been approved in the United States. It prevents the disease in infants, but pregnant women receive it.
The new vaccine that prevents bronchiolitis and was approved this week by the FDA in the United States.
This Monday, the United States became the first country to authorize a vaccine that could trigger a revolution in pediatrics: the respiratory syncytial virus (RSV) vaccine. It is the one that causes bronchiolitis, a respiratory disease that annually kills 100,000 children under one year of age in the world and that every autumn/winter overflows pediatric wards.
This is what happened in Argentina in May, when the increased demand was added to the crisis due to the shortage of pediatricians and a collapse in care was generated. Because bronchiolitis is one of the main causes of hospitalization in infants: according to data from the latest Epidemiological Bulletin of the Ministry of Health, this season there were more than 143,000 children under two years of age with bronchiolitis. Some 11,000 infants under one year of age were hospitalized for respiratory infections and approximately 70% had respiratory syncytial virus.
This new vaccine, from the U.S. laboratory Pfizer, had already been authorized by the U.S. FDA in May for people over 60 years of age. It received a recommendation from the European health authority, the EMA, but the European Commission has not yet decided whether to approve its marketing on the continent.
As Clarín has learned from official sources, Pfizer submitted the authorization request to ANMAT, which is evaluating it and there is still no estimated date of resolution.
What we do have are the results of the clinical trial, in which 7,000 pregnant women participated and in which Argentina was one of the countries that contributed the most volunteers. And they were very positive in terms of efficacy: the risk of serious disease in their children was reduced by 81.8% in the 90 days after birth and by 69.4% within 180 days. In a subgroup in which they received the vaccine between 32 and 36 weeks of gestation, the risk was further reduced: 91.1% at 90 days and 75.5% at 180 days. That is why the FDA's indication is to administer the vaccine between those weeks of gestation.
Among the most frequent side effects in vaccinated pregnant women were discomfort at the injection site, headache or muscle pain, and nausea. Preeclampsia, the increase in blood pressure in pregnancy, was reported in 1.8% of cases versus 1.4% of those who received a placebo. And there were also more preterm births (5.7% vs. 4.7%), so the FDA called for further study of these two issues.
How the vaccine works
Gonzalo Pérez Marc is the principal investigator of the study he led at the Hospital Militar Central, but in which centers from all over the country also participated. He is ecstatic: he says that bronchiolitis "is not just any disease" and that all doctors, when they start their Pediatrics residency in the middle of the year, spend three months without sleep battling RSV. For him, fighting this virus has also become an obsession in his role as a scientist: more than half of the 15 years he has been doing research has been devoted to RSV.
Gonzalo Pérez Marc, the researcher at the Hospital Militar Central who led the study of the vaccine in Argentina.
The same happens with the influenza vaccine: the aim is for the mother to generate a good amount of antibodies, pass them through the placenta andthe baby is born with mature antibodies. "The challenge is threefold. To achieve a good immune response in the mother, for the vaccine to be safe and for there to be a good transplacental passage. From then on, you set certain milestones and evaluate at three months and six months," he explains.
What happens after six months? As we already learned with Covid, with the vaccine rolling , its effectiveness, which is the efficacy measured in the real world, will be evaluated. "As with all respiratory viruses, after six months, antibodies decline. But what you are mainly looking to cover is up to six months, with the highest risk of severe disease," he points out. Going back to the Epidemiological Bulletin, the data support it: in the 12 to 24 months age group, there were about 2,000 hospitalized patients with RSV, and a similar number between two and four years old.
Roberto Debbag, president of the Latin American Society of Pediatric Infectious Diseases, agrees on the impact of respiratory syncytial virus and the importance of having a vaccine. "One in three children or more in Latin America will suffer bronchiolitis in their first year of life," he says, categorically. And he points out that RSV, together with pneumococcus and Haemophilus influenzae bacteria, are the three respiratory diseases that cause the greatest mortality at that stage of life.
If severe disease is reduced, says Debbag, there are fewer hospitalized patients and greater capacity of health systems to attend to other pathologies. But he adds another important variable, which Pérez Marc also warns about: the number of children who die from RSV without knowing it.
"There is a percentage of children who do not reach the health system and die, and they belong to vulnerable populations in Latin America and Argentina: poor, ethnic and migrant children," he warns.
For him, the new vaccine "is a tool that will change the history of RSV morbidity and mortality". And he added, as Pérez Marc also pointed out, that the application of a single-dose monoclonal antibody is advancing in the world's regulatory agencies, which would make it possible to draw up a preventive strategy to deal with this virus.
Respiratory syncytial virus, under the microscope. Photo AP
Pérez Marc explains that in the case of children at risk, they will be able to complement the vaccination with this new drug once the antibodies in the vaccine have naturally decayed. And he says that the research does not end here: next year his group will start testing the same vaccine in the pediatric population, in order to have a complete preventive "combo".
In this uncertain electoral context, no one can say what will happen with the access to this vaccine, if it finally meets all the requirements for ANMAT to approve it. There are no precisions as to how much it would cost, and the laboratory did not provide any information on the matter. The incorporation of a vaccine to the national calendar is analyzed by the National Immunization Commission, which is the one that recommends it or not and then the Ministry of Health determines it according to the health strategies and its cost-effectiveness.
The specialist explains that this vaccine is a pre-fusion protein vaccine (one of those used by the virus before binding to the cell), which makes it much more stable than those previously developed, and that it can be easily stored in the refrigerator. In addition, another vaccine, with messenger RNA technology, is being studied.
