Source: Infobae | By Valeria Chavez
The country was the first to immunize pregnant women to protect babies in the first months of life, when they are most vulnerable to respiratory syncytial virus infections. Research showed the impact on preventing serious illness and hospitalizations.
In March 2024, Argentina became the first country in the world to incorporate the bivalent pre-fusion F vaccine (RSVpreF) against Respiratory Syncytial Virus (RSV) in its national vaccination schedule for pregnant women.
This breakthrough in the fight against RSV was backed up by a recent study published in The Lancet Infectious Diseaseswhich validates the effectiveness of the vaccine in preventing hospitalizations and improving the clinical course of infants affected by this virus.
The study, conducted in 12 hospitals in Argentina, offers promising results for public health in the country and could serve as a model for other nations.
This multicenter study, known as the BERNI study, took place between April and September 2024 in 12 public and private hospitals in Argentina. Its objective was to evaluate the effectiveness of the bivalent prefusion F vaccine (RSVpreF) in infants born to mothers who received the vaccine between 32 and 36 weeks of gestation.
Researchers analyzed 505 infants hospitalized for severe respiratory infections, especially bronchiolitis, to determine the impact of maternal immunization.
The results of the study were encouraging: the vaccine was 78.6% effective in preventing RSV hospitalizations in infants under 3 months of age and 71.3% in infants up to 6 months of age. These percentages are close to the results obtained in previous clinical trials, where the efficacy was 82.4% at 3 months and 70% at 6 months.
The study also showed that vaccinated infants who still required hospitalization had a more favorable clinical outcome than unvaccinated infants. In total, three RSV-associated deaths were reported, all in infants born to mothers who did not receive the vaccine.
Mauricio Caballero is a pediatrician (MN 132,990), director of the Infant Center of Translational Medicine of the Universidad Nacional de San Martín(Unsam), Conicet researcher, and consulted by Infobae he said that "it is a very important finding because it allows emphasizing the implementation of vaccination with this vaccine in Argentina, improving the coverage rates and also this information is essential for those countries that have not yet implemented this vaccine, which shows to be effective for the prevention of serious cases of syncytial infection and also proves to be safe".
"We even saw efficacy in those where the vaccine would not seem to be effective in avoiding hospitalization," pediatrician and researcher Gonzalo Pérez Marc (MN 110,813), general director of Equipo Ciencia, told Infobae . "Because although they were hospitalized, a lower severity of symptoms was evaluated in babies whose mothers had been vaccinated compared to those who had not."
"There were only three deaths from severe bronchiolitis detected in the entire study and all were children of unvaccinated mothers," he remarked.
Inclusion of the vaccine in the National Vaccination Schedule
On March 1, 2024, Argentina started to apply the RSV vaccine as part of the National Vaccination Calendar. This strategy is aimed at pregnant women between 32 and 36 weeks of gestation, with the objective of transferring the antibodies to the baby through the placenta, providing protection during the first six months of life.
This is the period when infants are most vulnerable to severe RSV infections, which can cause bronchiolitis and pneumonia, conditions that lead to a large number of hospitalizations.
"This vaccine is very important because RSV is the leading cause of morbidity and mortality in pediatrics due to respiratory viruses," said Pérez Marc, "And it always affects mainly the most vulnerable, from birth to the first 6 months of age, especially the first 3 months," he stressed.
The incorporation of this vaccine into the national schedule is a milestone for public health, since Argentina is the first country to adopt this measure on a mandatory and free basis. This could represent a model for other nations, especially those with a high prevalence of RSV in the infant population.
Global impact of respiratory syncytial virus
RSV is a leading cause of bronchiolitis and hospitalization for lower respiratory infections (LRTI ) in children under 5 years of age.
Worldwide, the virus causes approximately 33 million cases of ARIB in young children annually, of which about 3.6 million require hospitalization. In addition, it is estimated that up to 100,000 deaths per year are caused by RSV-associated complications, with infants under 6 months of age being the most affected.
In Argentina, RSV represents a major burden for healthcare systems. Every winter, pediatric nurseries are overwhelmed by the increase in cases of bronchiolitis, which overloads hospitals and affects both families and medical staff. According to official data, approximately 260,000 cases of bronchiolitis are reported annually in children under two years of age.
The idea of this paper is that its results can be translated to different regions of the world where the vaccine has not yet been implemented and where mortality is very high," Caballero emphasized. Ninety-eight percent of deaths related to respiratory syncytial virus in young infants occur in poor countries, and 70% of deaths occur at the community level".
Complementary prevention and treatment strategies
In addition to the vaccine for pregnant women, there are other tools to prevent severe RSV infections in infants.
One of them is the use of monoclonal antibodiesOne is the use of monoclonal antibodies, such as Palivizumab and Nirsevimab, which are intended for high-risk infants, such as premature infants or those with cardiovascular disease. These monoclonal antibodies help prevent serious infections during the virus circulation season.
In terms of research, the development of a nasal vaccine for infants between 6 and 22 months is underway. This new approach is in phase III clinical trials and seeks to offer direct protection in the upper respiratory tract, which could reduce both the severity of the disease and its transmission among the very young.
Implications for public health and the future of vaccination.
The study published in The Lancet reinforces the importance of maternal vaccination as a strategy to combat RSV. The effectiveness observed in this study is consistent with the results of previous clinical trials and suggests that the vaccine has a significant impact on reducing hospitalizations and improving the clinical outcome of infants infected with RSV.
However, experts caution that the true magnitude of the vaccine's impact can only be fully assessed when vaccination coverage increases in the coming years.
Although only 62.5% of the target population was vaccinated in 2024, mass vaccination in subsequent years is expected to further reduce child mortality and the burden on health systems.
In addition, the success of the program in Argentina could serve as a model for other countries with a high burden of RSV in children to consider incorporating this vaccine into their national immunization schedules.
The study and the results obtained in Argentina demonstrate the effectiveness of the bivalent prefusion F vaccine (RSVpreF) against Respiratory Syncytial Virus, especially in the prevention of hospitalizations and in the improvement of the clinical evolution of infants affected by this virus.
This breakthrough represents an important step in the fight against one of the leading causes of childhood hospitalization in the world and could have significant implications for global public health.
"These results are fundamental to continue to trust and stimulate vaccination and increase coverage throughout the country, throughout the region and encourage countries that have not yet implemented this strategy," considered Perez Marc.
To conclude, Caballero said that his working group at the Infant Center "is developing a federal study in 30 hospitals and seven morgues in the metropolitan area of Buenos Aires, in order to determine not only the effectiveness of the vaccine in the prevention of hospitalizations, admission to intensive care or serious illness, but also to determine the effectiveness of the vaccine in reducing infant mortality".
