RSV Prevention in All Infants: Which Is the Most Preferable Strategy?

Abstract

Respiratory syncytial virus (RSV) causes a spectrum of respiratory illnesses in infants and young children that may lead to hospitalizations and a substantial number of outpatient visits, which result in a huge economic and healthcare burden. Most hospitalizations happen in otherwise healthy infants, highlighting the need to protect all infants against RSV. Moreover, there is evidence on the association between early-life RSV respiratory illness and recurrent wheezing/asthma-like symptoms As such, RSV is considered a global health priority. However, despite this, the only prevention strategy currently available is palivizumab, a monoclonal antibody (mAb) indicated in a subset of preterm infants or those with comorbidities, hence leaving the majority of the infant population unprotected against this virus. Therefore, development of prevention strategies against RSV for all infants entering their first RSV season constitutes a large unmet medical need. The aim of this review is to explore different immunization approaches to protect all infants against RSV. Prevention strategies include maternal immunization, immunization of infants with vaccines, immunization of infants with licensed mAbs (palivizumab), and immunization of infants with long-acting mAbs (e.g., nirsevimab, MK-1654). Of these, palivizumab use is restricted to a small population of infants and does not offer a solution for all-infant protection, whereas vaccine development in infants has encountered various challenges, including the immaturity of the infant immune system, highlighting that future pediatric vaccines will most likely be used in older infants (>6 months of age) and children. Consequently, maternal immunization and immunization of infants with long-acting mAbs represent the two feasible strategies for protection of all infants against RSV. Here, we present considerations regarding these two strategies covering key areas which include mechanism of action, “consistency” of protection, RSV variability, duration of protection, flexibility and optimal timing of immunization, benefit for the mother, programmatic implementation, and acceptance of each strategy by key stakeholders. We conclude that, based on current data, immunization of infants with long-acting mAbs might represent the most effective approach for protecting all infants entering their first RSV season.

Changes in clinical, demographic, and outcome patterns of children hospitalized with non‐SARS‐CoV‐2 viral low respiratory tract infections before and during the COVID pandemic in Rome, Italy

“…These findings are somehow in line with our study and suggest that the resurgence of viral circulation after the initial pandemic period might have had a specific significant impact on older children, while a typical impact on the younger ones. Reasons for these changes still need to be fully elucidated, 21,22 and will require future monitoring, also based on the new strategies that will be soon implemented against RSV 23–26 . At current state of knowledge, it is difficult to understand if the pathogenicity of the pathogens has changed, or the responses of children to pathogens changed, either due to limited previous exposures or to other concomitant factors, including previous SARS‐CoV‐2 infection.…”

“…Reasons for these changes still need to be fully elucidated, 21,22 and will require future monitoring, also based on the new strategies that will be soon implemented against RSV. [23][24][25][26] A possible role of co-infections in a more severe impact of LRTI in children cannot be excluded. During the first year of the pandemic, most viruses almost disappeared, 4,18 showing a rebound since 2021.…”

Characterisation of RSV infections in children without chronic diseases aged 0–36 months during the post-COVID-19 winter season 2022/2023

“…In autumn 2023, the RSV vaccine Abrysvo TM was approved in Austria for pregnant women between the 24th and 36th week of pregnancy (41). Immunization of the mother leads to passive transfer of maternal antibodies via the placenta to the fetus to prevent RSV disease in early infancy (42)(43)(44). This happens before an active vaccination can generate an effective immune response in infants leading to a protection directly after (45).…”

Monoclonal antibodies for prophylaxis and therapy of respiratory syncytial virus, SARS-CoV-2, human immunodeficiency virus, rabies and bacterial infections: an update from the World Association of Infectious Diseases and Immunological Disorders and the Italian Society of Antinfective Therapy

“…These findings, together with relatively low price, made several experts think that a universal use of RSV prophylaxis in children was possible ( 47 – 49 ). Instead of a few, highly selected, children, these new mABs could have allowed the protection from RSV disease and related problems all the infants and toddlers.…”