Thousands of infants catch respiratory syncytial virus (RSV) each year. While most cases are mild, the virus can cause severe breathing problems in newborns and require hospital treatment. A new report shows that RSV admissions among infants fell sharply after Denmark began offering the vaccine to pregnant women in fall 2025.

Key takeaways

  • Denmark started offering an RSV vaccine to pregnant women in fall 2025 to protect newborns during their first months of life.
  • Following the rollout, hospital admissions for RSV among infants dropped sharply, according to the report.
  • The findings suggest that vaccinating pregnant women can significantly reduce severe RSV illness in young infants.

The vaccine and its timing

Since fall 2025, pregnant women in Denmark have been offered an RSV vaccine. The goal is to boost the mother’s antibodies, which then pass to the baby through the placenta. This protection helps shield infants during the first few months of life, when they are most vulnerable to severe RSV infection.

The vaccine is given late in pregnancy, typically during the third trimester. This timing ensures that the baby receives a high level of antibodies at birth and in the weeks that follow. The approach is similar to how the Tdap vaccine (for tetanus, diphtheria, and pertussis) is used during pregnancy to protect newborns from whooping cough.

Impact on hospital admissions

The new report, described by Medical Xpress, examined RSV hospitalization rates among infants in Denmark before and after the vaccine rollout. The data showed a sharp decline in admissions after the program began. While the exact numbers were not provided in the summary, the drop was described as significant.

RSV is a leading cause of hospitalization in infants worldwide. In severe cases, the virus can cause bronchiolitis and pneumonia, requiring oxygen support or mechanical ventilation. The reduction in admissions suggests that the maternal vaccine is effectively preventing the most serious outcomes.

Implications for public health

The findings from Denmark add to growing evidence that maternal RSV vaccination can protect very young infants. Several countries are now considering or implementing similar programs. The vaccine offers a way to reduce the burden on hospitals during RSV season, which typically peaks in winter months.

Public health officials hope that widespread use of the vaccine could lower the number of infant RSV hospitalizations by a large margin. This would not only improve outcomes for babies but also ease pressure on pediatric intensive care units.

How the vaccine works

The RSV vaccine given to pregnant women is designed to stimulate the immune system to produce antibodies against the virus. These antibodies cross the placenta and provide passive immunity to the newborn. The protection lasts for several months, covering the period when infants are at highest risk.

Clinical trials have shown that the vaccine is safe for both mother and baby. Common side effects include injection site pain, fatigue, and mild fever. Serious adverse events are rare. The vaccine does not contain live virus, so it cannot cause RSV infection.

Frequently Asked Questions

Who should get the RSV vaccine during pregnancy?

The vaccine is recommended for pregnant women in their third trimester, typically between 32 and 36 weeks of pregnancy. This timing maximizes the transfer of antibodies to the baby. Women should consult their healthcare provider to determine if the vaccine is appropriate for them.

How effective is the maternal RSV vaccine?

Based on clinical trials and real-world data from Denmark, the vaccine significantly reduces the risk of severe RSV infection in infants during their first six months of life. The exact effectiveness can vary depending on factors such as timing of vaccination and circulating RSV strains.

Is the RSV vaccine safe for the baby?

Yes, the vaccine has been studied extensively and is considered safe for both pregnant women and their babies. It does not contain live virus and cannot cause RSV infection. Side effects are generally mild and temporary. The benefits of preventing severe RSV disease outweigh the risks for most women.

This is an original report by Vital Signs Today, informed by reporting from Medical Xpress. Read the original source.

This article is for information only and is not medical advice. See our Medical Disclaimer.