Ways to protect infants

The first systematic preventive intervention against RSV was palivizumab, approved in 1998. This monoclonal antibody binds the RSV F (fusion) protein and is given by monthly intramuscular injection. Randomised controlled trials found that it reduced RSV-related hospital admission by around 40–50% in preterm infants and those with chronic lung or congenital heart disease.12

Its critical limitation from a public health perspective is that it requires monthly repetition, is expensive, and covers only defined risk categories.20 These features formed the structural basis for decades of treating RSV prevention as a narrow subgroup issue. Palivizumab is clinically valuable, but it cannot underpin a population-level strategy.

Nirsevimab, approved by the European Medicines Agency (EMA) in 2022 and the US Food and Drug Administration (FDA) in 2023, represents a turning point.34

It is a next-generation monoclonal antibody targeting the pre-fusion conformation of the RSV F protein, with a long half-life and given as a single dose. Thanks to its extended half-life, a single dose is intended to reduce the risk of RSV-related lower respiratory tract disease over a period of roughly five to six months.

Its fundamental difference from palivizumab is not the mechanism but the population it targets. All infants, regardless of risk category, can be protected for a season with a single dose. This is what makes it possible, for the first time, to design RSV protection as a genuine population-level infant health strategy.

After nirsevimab came into widespread use in the USA and France in the 2023–2024 season, real-world data consistently supported the phase 3 findings. Early data compiled from the CDC-run RSV-NET and NVSN platforms showed a reduction of more than 90% in RSV-related hospital admissions among infants who received it. National data from France point to a field effectiveness of around 83%.78

The other significant intervention is RSV vaccination given to the expectant mother. The bivalent pre-fusion F protein vaccine, approved by the FDA in 2023, is given between 32 and 36 weeks of gestation; the mother's immune response is transferred across the placenta so that the newborn is protected passively in the first months of life.1213

The MATISSE trial was a phase 3 study of more than 7,400 women vaccinated between 24 and 36 weeks of gestation. Efficacy against severe RSV-associated lower respiratory illness was reported as 81.8% in the first three months after birth and 69.4% over the first six months. The fact that protection is highest in the first weeks after birth is a critical advantage of maternal vaccination for the early neonatal period.11

However high individual effectiveness may be, the most critical variable determining population-level public health impact is coverage. Modelling shows that where coverage stays below 50%, system-level reductions in hospital admissions are very limited; as coverage rises into the 70–80% range, systemic gains multiply.

In maternal vaccination programmes, factors such as gestational week, timing of birth and access to antenatal care can affect coverage. In some nirsevimab programmes, combining delivery-unit and primary care administration has been reported to achieve coverage above 90%.910 These results may vary between countries and delivery models.

Delivery data from Spain make the cost effect of timing concrete. The number of infants needed to immunise (NNI) to prevent one RSV admission was 41 in the delivery-room group (estimated cost ~€9,000), rising to 90 in the catch-up group, where cost more than doubled.17 This gap demonstrates the budget impact of running immunisation predominantly through birth units.

For Türkiye, the national RSV economic burden study has quantified the financial load RSV infections place on the health system through hospital admissions, intensive care expenditure and parental work loss.16

Türkiye's family medicine and hospital infrastructure offers significant capacity that could be assessed for a possible national delivery model. Hospital-based administration for infants born during the season, and access through primary care for those born before it, are among the models used in international examples.

International experience consistently shows that the highest and most homogeneous coverage is achieved through hybrid models combining hospital-based initiation with primary care integration.7918 Where delivery depends on a single channel, coverage is more limited and it becomes harder to include infants born late in the season or lost to follow-up.