Protection against respiratory syncytial virus (RSV) must be extended to lower-income countries, which are harder hit.Credit: Hailshadow/Getty
“There is something wrong with the data. There are too few people in hospitals” with respiratory syncytial virus (RSV), recalls epidemiologist Caroline Klint Johannesen, who remarked to a colleague while analyzing Danish health records from last winter.
On October 1, 2025, Denmark introduced a national policy to vaccinate pregnant people against RSV, a respiratory pathogen that usually causes mild symptoms but can lead to severe illness and even death in vulnerable people, including infants and the elderly. Maternal antibodies induced by the vaccine cross the placenta to protect babies for about the first six months of life, when they are most at risk. Newborns at high risk of serious illness, including premature babies whose mothers had not been vaccinated, received injections of monoclonal antibodies.
RSV wave hits hospitals – but vaccines and treatments are coming
Johannesen, a vaccine researcher at Nordsjællands Hospital in Hillerød, Denmark, discovered1 that infant hospital admissions have fallen. Vaccinations work, she says (see “Protecting the Newborn”).
Global risks
The World Health Organization (WHO) estimates that each year, RSV hospitalizes approximately 3.6 million people and kills approximately 100,000 children under the age of 5. Of these deaths, 97% occur in low- and middle-income countries (LMICs).
The virus is also dangerous for older people – although these risks are largely underestimated by both doctors and the public. Historically, testing has been rare and there are no global statistics on RSV-related adult deaths. But beyond age 60, hospitalizations and mortality increase with age, especially among people with other illnesses such as chronic heart and lung disease. In the United States, the Centers for Disease Control and Prevention (CDC) estimates that between 10,000 and 25,000 people died in each of the last two winters, particularly in older age groups.
Source: Ref. 1
Since 2022, when European regulators approved nirsevimab – a long-acting monoclonal antibody against RSV – a second antibody and three vaccines have been developed for use in adults, including one suitable for pregnant people.
“It’s just remarkable,” says Buddy Creech, a pediatrician at Vanderbilt University in Nashville, Tennessee, to have gone “from having no mechanism to prevent RSV to an embarrassment of riches.” Dozens of countries in Europe, Asia and North and South America have launched various vaccination programs.
Up to date vaccinations
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