Maternal RSV vaccines reduce infant hospitalizations in Denmark

Caroline Klint Johannesen, a vaccine researcher at Nordsjællands Hospital in Hilleroed, Denmark, found that infant hospital admissions plummeted following a nationwide vaccination policy.

Denmark implemented a policy on 1 October 2025 to vaccinate pregnant people against respiratory syncytial virus (RSV). The vaccine allows maternal antibodies to cross the placenta, providing protection for babies during their first 6 months of life when they are most vulnerable to the respiratory pathogen.

The World Health Organization estimates that RSV hospitalizes roughly 3.6 million people and kills about 100,000 children under 5 years old annually. The majority of these childhood deaths, 97 percent, occur in low- and middle-income countries. While the virus often causes mild symptoms, it can lead to severe disease or death in infants and older adults. The virus also poses a serious risk to people over the age of 60, particularly those with chronic heart or lung conditions.

In the United States, the Centers for Disease Control and Prevention estimates that between 10,000 and 25,000 people died from RSV during each of the past two winters. Since 2022, several new treatments including nirsevimab and various vaccines have been developed to combat the virus in adults and pregnant people.