“Something’s wrong with the data. There are too few people in hospitals” with respiratory syncytial virus, epidemiologist Caroline Klint Johannesen recalls a colleague remarking while analysing Danish health records for last winter, Nature reported.
Infant hospital admissions plummeted after Denmark introduced a nationwide policy of vaccinating pregnant people against the respiratory pathogen on October 1, 2025. Based on findings published by Nature, the immunization generates maternal antibodies that traverse the placenta, safeguarding infants during roughly their initial half-year of life when vulnerability peaks.
- Maternal Immunization: Vaccinating during pregnancy passes protective antibodies directly to the developing fetus across the placenta, shielding newborns during their vulnerable first six months of life.
- Targeted Monoclonal Protection: Newborns at high risk of severe disease, including premature infants whose mothers were unvaccinated, receive direct injections of monoclonal antibodies to neutralize the respiratory syncytial virus.
- Hospital Admission Drop: Real-world health record analysis in Denmark demonstrates that these coordinated immunization policies successfully slash severe infant infections and clear hospital wards.
The World Health Organization estimates that every year, respiratory syncytial virus hospitalizes roughly 3.6 million and kills about 100,000 children under 5 years old. Of these deaths, 97% occur in low- and middle-income countries, Nature reported. Protection against the pathogen must expand to these lower-income countries, which are harder hit, as noted by Nature.
Older adults also face significant threats from the pathogen, even though medical professionals and society generally fail to recognize these dangers. Historically, testing has been sparse, and there are no global statistics for deaths related to the virus among adults.
As Nature noted, hospitalization rates and fatalities climb past age 60, most notably among individuals suffering from pre-existing illnesses like chronic pulmonary and cardiac ailments. According to figures from the Centers for Disease Control and Prevention, US fatalities ranged from roughly 10,000 to 25,000 during each of the prior two winter seasons, heavily impacting older demographics.
Nature said that European regulators greenlit nirsevimab—an extended-release monoclonal antibody targeting the pathogen—back in 2022, which has since been followed by the creation of three adult vaccines and a second antibody option, with one vaccine specifically cleared for expecting mothers.
“It’s just remarkable,” Buddy Creech, a paediatrician at Vanderbilt University in Nashville, Tennessee, told Nature, to have gone “from no mechanism to prevent RSV to an embarrassment of riches.” Dozens of countries across Europe, Asia and North and South America have launched various immunization programmes, according to Nature.
| Intervention Type | Target Population | Mechanism of Action |
|---|---|---|
| Maternal Vaccine | Pregnant individuals | Induces maternal antibodies that cross the placenta to protect infants |
| High-risk newborns and premature infants | Delivers passive immunity directly via targeted antibody injections | |
| Older adults (aged 60+) |
- Nature: RSV vaccines slash infections: data show jabs’ staggering success against dangerous virus
- World Health Organization: Global estimates of RSV in children under 5
- Centers for Disease Control and Prevention: RSV mortality and morbidity data in older adults
- Nature: RSV wave hammers hospitals — but vaccines and treatments are coming
