Nearly 70 years later, there are vaccines for the main cause of bronchiolitis in children. What is the expected effect? | Science and health

In 1956, scientists first identified respiratory syncytial virus (RSV), a pathogen known to many pediatricians as the primary cause of bronchiolitis under the age of 2 years. In the 1960s, the first vaccine tests began to stop the pathogen. However, after a series of unsuccessful clinical trials, the world finally approved the first vaccine against RSV in 2023, almost seven decades later.

Experts say the green light was cause for celebration, because the effect of the virus is similar to that seen in other pathogens that cause respiratory illness, such as influenza. Data from Fiocruz's Infogripe project, which is based on the Influenza Epidemiological Surveillance Information System (Sivep-Gripe), reveal this burden.

In 2023, there were 179,000 cases of severe acute respiratory syndrome (SARS), requiring hospitalization, in the country, 71.2 thousand of which were confirmed by laboratory results to be infected with a respiratory virus. Of these cases, 23,000 were caused by respiratory syncytial virus, or 32.4% of the total, second only to Covid-19. The vast majority of them, 19.7 thousand, were children under the age of two – 85.4% of the total.

Furthermore, when looking at age group only, the impact of RSV is greater than that of COVID-19, with the virus responding more than five times as much as MERS-CoV. This effect increases the burden on hospital units during the period of greatest spread of pathogens, generally between May and July.

— The number of cases is very high under two years and is a frequent cause of hospital admission resulting in a significant impact on public and private health services. Neonatal intensive care units are full of babies infected with RSV – says Professor of Infectious Diseases at the State University of Campinas (Unicamp) and Advisor to the Brazilian Society of Infectious Diseases (SBI), Raquel Stucci.

The virus is not only affecting the youngest, but people over the age of 65 also face a high burden of disease. There is not good monitoring of numbers in the age group, explains pediatrician and director of the Brazilian Society for Immunizations (SBIm), Isabella Palalay, but estimates by the US Centers for Disease Control and Prevention (CDC), for example, indicate up to 10,000 deaths per year. Among the elderly due to respiratory syncytial virus in North American countries.

— In Brazil, due to the lack of laboratory diagnosis, we do not have precise data on the impact on this age group. We need to monitor cases in elderly people to know what the real situation is. But in other countries, where this has been studied for a long time, we see that the impact is greater, with deaths ranging from 45% to 50%.

What vaccines are available?

The first vaccine to receive approval was Arexvy, developed by GlaxoSmith Kline (GSK). In December 2023, the National Health Surveillance Agency (Anvisa) also approved this in Brazil. It is targeted at seniors aged 60 and above and is applied in a single dose.

At the moment, it is only available on the private market, at prices up to R$1,704.15, as determined by the Chamber of Medicines Market Regulation (CMED). On average, it can be found for R $ 1,650 in clinics and pharmacies throughout the country. In phase III clinical studies, it was 82.6% effective in preventing lower respiratory tract infection (LRTI) caused by respiratory syncytial virus, and 94.1% effective in preventing severe cases of LRTI.

In April this year, Anvisa, following the US movement, approved a second vaccine, Apresvo, a single-dose vaccine developed by the US pharmaceutical company Pfizer. The difference is that in addition to the elderly, the application also targets pregnant women, during the second or third trimester of pregnancy, with the aim of transferring protection to the child.

In the third phase of clinical studies, the strategy succeeded in reducing cases of acute respiratory diseases by 81.8% in the first three months of a newborn’s life, and by 69.4% six months after birth. Among older adults, efficacy was 88.9% against DTRI during the first season of surge, and 77.8% during the second season.

—Both vaccines have demonstrated significant efficacy in clinical studies and are considered safe, with well-established safety profiles. These are important achievements, because after decades of research and development, we now have effective tools to prevent a disease that causes thousands of hospitalizations and deaths every year – says Leonardo Wiseman, an infectious disease specialist at the Emilio Ribas Institute of Infectology, in São Paulo. He is a professor at the University of Ribeirão Preto (UNAERP).

But the Pfizer dose is not yet available in the Brazilian market. After obtaining the license, it still has to go through the pricing process with CMED so that it can then be displayed. SBIM's Palalay says it is expected to arrive in the country in the second half of the year.

Moreover, there is a third vaccine approved on the 31st in the United States, intended for the elderly, but it has not yet been analyzed in Brazil. It is also a single dose developed by the Moderna laboratory with the same technology as the Covid-19 vaccine, messenger RNA.

What is the expected effect?

Given the effectiveness of the doses, experts interviewed by Globo emphasized that those who receive the vaccines will receive high individual protection. However, to monitor the impact on the disease curve, they explained that it would be necessary to integrate vaccination into the Unified Health System (SUS) to achieve high vaccination coverage.

—Experience with other respiratory vaccines, such as influenza, suggests that with high vaccination coverage, we may see significant reductions in morbidity and mortality in the coming years, favorably changing the epidemiology of the disease. Incorporating doses against respiratory syncytial virus into SUS would be very beneficial, Weisman says.

This is what Palalai also thinks: — I would really like them to be integrated into the unified health system, because in order to see an impact on disease numbers, we need this vaccination coverage. This is far from happening now, because we only have one vaccine available, and it is only available on the private network and is very expensive. We will only have coverage when it is included in PNI.

In order to be offered on the public network, vaccines must be ordered from the National Committee for Technology Integration of SUS (Conitec) by pharmaceutical companies or Brazilian health authorities. It is the body that evaluates the cost and benefit and gives an opinion, whether it proposes inclusion or not. Ultimately, the decision rests with the Ministry of Health.

— Incorporation of any and all vaccines into the common system will depend on the availability of the manufacturer's production and the cost of these doses. This will be important because these infections have a major impact on healthcare services. If this happened, they would likely be recommended for pregnant women, to protect their babies, and for adults over 60, perhaps focusing on those with comorbidities, who are at higher risk of serious disease – according to Stucci's assessment.