Maternal RSV Vaccine Shows Improved Protection Among Infants

Despite no existing respiratory syncytial virus (RSV) vaccine reserved for infants, maternal vaccines have demonstrated longer protection than monoclonal antibodies (mAbs), according to a study published in the Journal of Mother and Child.¹

“RSV is a prevalent cause of upper respiratory tract infections (URTI), and can progress to lower respiratory tract infections (LRTI), particularly in vulnerable groups, such as infants, immunocompromised individuals, and the elderly,” wrote authors of the study. “Beyond causing immediate illness, RSV infections in infancy have been linked to persistent wheezing and the long-term development of asthma.”

For infants, their mothers, and the providers that care for them, RSV is one of the most challenging health-related complications that they face. According to a study from Human Vaccines & Immunotherapeutics, RSV-related LRTI are responsible for up to 3 million hospitalizations and 120,000 deaths each year among children under 5.²

In over 50 years of vaccine development, researchers have yet to establish a universal option for protecting infants against RSV. | image credit: Berit Kessler / stock.adobe.com

READ MORE: Pharmacist, Provider Partnership Can Help Increase RSV Vaccine Uptake

Previous evidence shows that the most at-risk populations when it comes to RSV, URTI, and LRTI are infants and elderly adults 65 or over. While the elderly population have 3 RSV vaccine formulations available—Abrysvo, Arexvy, or Mresvia—the RSV antibody nirsevimab for children younger than 8 months is the frontline option for keeping them protected against LRTI and URTI.^3,4

Authors of the current study and CDC recommendations have supported evidence that mothers who receive the RSV vaccine can pass antibodies to their newborns, providing protection against RSV for up to the child’s first 6 months.^1,4

“Immunization is a key approach for protecting infants and children against RSV, either whether it is passive immunization via mAbs and maternal antibodies, or active immunization via RSV vaccination,” they continued.¹ “This narrative review aims to critically compare various immunization methods for children against RSV, discussing the strengths, limitations, and future directions of each.”

In over 50 years of vaccine development, researchers have persistently failed at bringing an RSV vaccine to market for protection among infants. With no methods of keeping one of the more at-risk populations protected, researchers later developed palivizumab as a mAb option available for infants. Since then, in 2023, the FDA approved nirsevimab for its similar effects among infants, but its availability is known to be limited.

“Palivizumab’s use is confined to a narrow segment of the pediatric population—those under 35 weeks of gestational age and those up to 6 months of age at the RSV season's onset, along with individuals with specific underlying conditions,” wrote the authors.¹ “Consequently, most infants remain unprotected against RSV. Therefore, protecting all infants up to 6 months of age is only possible through maternal immunization or using extended duration mAbs.”

Maternal immunization, or transplacental antibody transfer, would be the alternative option for parents choosing not to directly vaccinate their infants with mAbs. And as a significant amount of evidence suggests, this may be the best option for protecting children against RSV. If timed right, toward the end of pregnancy, a mother receiving the RSV vaccine could provide the strongest protection for infants during their first, most vulnerable 6 months of life.

As of right now, the best method of maternal immunization is by vaccinating mothers between 32 and 36 weeks with Pfizer's bivalent RSVpreF vaccine (Abrysvo). However, despite this being the currently accepted approach for maternal immunization among children, many uncertainties persist regarding antibody detection and effects of the vaccine waning for mothers or their newborns.

Amid competing options for helping infants avoid RSV, researchers compared the 2 methods.

“Despite years of investigation, a dedicated RSV vaccine for children remains unavailable. However, recent FDA approval of maternal RSV vaccines has shifted the paradigm, as these vaccines provide longer-duration protection to infants compared to mAbs,” they wrote.¹ “Current guidelines recommend that if a mother receives the RSV vaccine during pregnancy, the infant from that pregnancy may not require mAbs.”

While recent developments of maternal RSV vaccines have exhibited continued success among infants, researchers still believe a personalized approach for mothers and their newborns is necessary. Despite maternal vaccines potentially demonstrating better efficacy than mAbs, insurance coverage, past RSV experiences, health care access, provider counsel, and existing RSV knowledge all play significant roles as factors influencing a mother’s choice to vaccinate.

As of January of this year, according to CDC data, 38% of pregnant women in the US were vaccinated against RSV, leaving a large majority of expected newborns with no protection against the virus upon birth. Other studies have reported that overall protection against RSV among infants was about 55.8%, with 44.6% provided the nirsevimab antibodies.⁶

Amid constant research and development, providers have yet to accept one universal approach in protecting newborn infants against RSV. And with large portions of the pregnant population failing to seek protection for their children, providers are tasked with navigating the various guidelines and which recommendations to provide specific patients.

Researchers hope the current study can better inform further developments of RSV vaccination strategies within this significantly at-risk population.

“Further clinical research is necessary to comprehensively compare the safety, efficacy, cost-effectiveness, and disease burden between infants whose mothers received the RSV vaccine and those whose mothers received mAbs,” concluded the authors.¹ “This study will contribute to a more informed and evidence-based approach to RSV immunization strategies for infants and children.”

READ MORE: Immunization Resource Center

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References

1. Ali A, Shamim L, Ibrahim A, et al. Maternal respiratory syncytial virus (RSV) vaccination: current status and comparison to monoclonal antibodies (mAbs) for RSV prevention in infants and children. JMC. Published online August 15, 2025:93-100. https://doi.org/10.34763/jmotherandchild.20252901.d-25-00012

2. Baraldi E, Checcucci Lisi G, Costantino C, et al. RSV disease in infants and young children: Can we see a brighter future? Hum Vaccin Immunother. 2022 Nov 30;18(4):2079322. doi: 10.1080/21645515.2022.2079322.

3. Respiratory syncytial virus (RSV): the disease, vaccines & monoclonal antibody. Children’s Hospital of Philadelphia. August 4, 2025. Accessed August 18, 2025. https://www.chop.edu/vaccine-education-center/vaccine-details/rsv-vaccine-monoclonal-antibody

4. Immunizations to protect infants. CDC. August 30, 2024. Accessed August 18, 2025. https://www.cdc.gov/rsv/vaccines/protect-infants.html

5. Respiratory syncytial virus (RSV) vaccination coverage, pregnant women, United States. CDC. April 9, 2025. Accessed August 18, 2025. https://www.cdc.gov/rsvvaxview/dashboard/pregnant-women-coverage.html

6. Soucheray S. Only 56% of US infants protected by RSV vaccine, antibody. University of Minnesota. September 30, 2024. Accessed August 18, 2025. https://www.cidrap.umn.edu/respiratory-syncytial-virus-rsv/only-56-us-infants-protected-rsv-vaccine-antibody-0