https://www.cidrap.umn.edu/respirat...show-rsv-immunizations-protect-newborns-their
Real-world studies show RSV immunizations protect newborns in their first year of life
Liz Szabo, MA
Today at 11:17 a.m.
Respiratory Syncytial Virus (RSV)
A pair of new studies confirm that recently developed immunizations against respiratory syncytial virus (RSV) protect infants in their first year of life.
The research, including one study conducted in France and another in the United Kingdom, confirm that the immunizations are effective in the real world, not just in carefully supervised clinical trials.
RSV hospitalizes 1.4 million babies around the world every year, making it the most common cause[JW1] of hospital admission for respiratory disease in infants. The virus kills nearly 46,000 babies under 6 months of age every year, according to the World Health Organization.
66% to 72% efficacy against hospitalization
The nationwide French study examined hospitalization rates in newborns given nirsevimab, an injection of ready-made antibodies against RSV, which first became available in 2023.
While vaccines prompt the body to make antibodies, a process that takes about two weeks, nirsevimab provides babies with ready-made, lab-grown antibodies that begin protecting them right away.
Newborns immunized with nirsevimab during the 2023 to 2024 respiratory season, which typically lasts from fall through early spring, were 66% less likely to be hospitalized with RSV, according to the study of nearly 75,000 infants, published this week in JAMA Pediatrics.
French newborns injected with nirsevimab during the 2024-25 season were 72% less likely to be hospitalized with RSV-related illness, according to the new study.
These two studies are real-world confirmations that current infant RSV prevention tools work.
Other real-world research has found that babies given nirsevimab are 85% to 90% less likely to be hospitalized for RSV-related illness. The authors of the article wrote that nirsevimab may have been less effective in the new study because of differences in the way their study was designed. For example, the new study included older babies born before the beginning of the French immunization campaign, who could be expected to have lower risk of RSV-related hospitalizations.
Protection fades over time
The researchers found that nirsevimab, sold in the United States under the brand name Beyfortus, protected infants during their first respiratory season only.
That finding isn’t surprising, given that nirsevimab is known to provide protection for only five months, according to authors of the study, led by the French National Agency for Medicines and Health Products Safety and French National Health Insurance.
Like all antibodies, the antibodies in nirsevimab, known as monoclonal antibodies, don’t last forever, said Amesh Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security who was not involved with the new study.
But Adalja notes that other studies have suggested that nirsevimab provides at least partial protection during an infant’s second respiratory season.
“The evidence on durability is mixed,” Adalja said.
A warning sign or ‘statistical noise’?
An earlier French study[JW2] found that babies immunized with nirsevimab had fewer ear infections.
In the new study, however, researchers found that babies immunized with nirsevimab had a small increase in the risk of being hospitalized with ear, nose, and throat infections. The study authors cautioned, however, that that risk was based on a small number of cases, and doesn’t outweigh the benefits of RSV immunization.
The increased risk of ear infections also could be a fluke.
“It may just be statistical noise in the data,” Adalja said. “It doesn’t have biological plausibility.”
Vaccinating pregnant people keeps babies out of the hospital
The British study focused on an RSV vaccine given in pregnancy, which prompts the immune system to create protective antibodies that can be passed on to the fetus.
Babies whose moms were vaccinated during weeks 28 to 31 of pregnancy were 61% less likely to be hospitalized for RSV than infants whose mothers weren’t vaccinated, according to a study of 694 babies published online July 1 in The Lancet Child & Adolescent Health. None of the newborns in the study received nirsevimab.
Those findings are similar to earlier research about the effectiveness of RSV shots in pregnant women, said James Campbell, MD, a professor of pediatrics and interim head of the Division of Infectious Diseases and Tropical Pediatrics at the University of Maryland School of Medicine. He wasn’t involved in the study.
Antibodies fade with time
Protection against RSV varied with the age of the baby. The youngest infants receiving the greatest benefit, likely because the antibodies tend to decline over time, Adalja said.
Although babies of vaccinated moms were 61% less likely to be hospitalized for RSV in the first six months of life, newborns under 3 months of age were 76% less likely, according to the study.
Pregnant study participants were vaccinated against RSV during weeks 28 to 31 of pregnancy. A typical pregnancy lasts 40 weeks.
All babies in the UK study, which was conducted from September 2025 to January 2026, were born after at least 28 weeks of pregnancy. Infants born before 37 weeks are considered premature; babies born from 28 to 32 weeks are considered very preterm. Babies born prematurely or very prematurely have higher risks for multiple health problems.
The study’s findings are in line with earlier real-world research. In those studies, babies whose moms are vaccinated at least two weeks before delivery were 58% to 82% less likely to be hospitalized for RSV, according to background material in the new article.
Studies confirm the importance of immunizing infants
“These two studies are real-world confirmations that current infant RSV prevention tools work,” Adalja said. “Both tools deliver strong protection during the window they’re designed to cover.”
The new studies present a very different picture of vaccines than given by President Donald Trump, who this week repeated long-debunked claims about immunizations and autism. Trump issued an executive order that aims to make RSV immunizations available only to babies at high risk.
Executive orders from the president are akin to all-staff memos from a company CEO. While they provide marching orders to people who work for the Trump administration, they have no legal bearing on doctors, medical organizations, or states.
Current immunization recommendations from US health organizations haven’t changed.
The American College of Obstetricians and Gynecologists recommends vaccinating pregnant people against RSV from weeks 32 to 36 of pregnancy.
The American Academy of Pediatrics (AAP) recommends that all infants whose moms weren’t vaccinated against RSV receive either nirsevimab or a newer drug, clesrovimab, before the age of 8 months, during or before their first RSV season. Children at high risk should be vaccinated again before their second RSV season, up to19 months of age, according to the AAP.
“These are both significant technologies that will change the paradigm of pediatric RSV—if they’re used,” Adalja said.
Real-world studies show RSV immunizations protect newborns in their first year of life
Liz Szabo, MA
Today at 11:17 a.m.
Respiratory Syncytial Virus (RSV)
A pair of new studies confirm that recently developed immunizations against respiratory syncytial virus (RSV) protect infants in their first year of life.
The research, including one study conducted in France and another in the United Kingdom, confirm that the immunizations are effective in the real world, not just in carefully supervised clinical trials.
RSV hospitalizes 1.4 million babies around the world every year, making it the most common cause[JW1] of hospital admission for respiratory disease in infants. The virus kills nearly 46,000 babies under 6 months of age every year, according to the World Health Organization.
66% to 72% efficacy against hospitalization
The nationwide French study examined hospitalization rates in newborns given nirsevimab, an injection of ready-made antibodies against RSV, which first became available in 2023.
While vaccines prompt the body to make antibodies, a process that takes about two weeks, nirsevimab provides babies with ready-made, lab-grown antibodies that begin protecting them right away.
Newborns immunized with nirsevimab during the 2023 to 2024 respiratory season, which typically lasts from fall through early spring, were 66% less likely to be hospitalized with RSV, according to the study of nearly 75,000 infants, published this week in JAMA Pediatrics.
French newborns injected with nirsevimab during the 2024-25 season were 72% less likely to be hospitalized with RSV-related illness, according to the new study.
These two studies are real-world confirmations that current infant RSV prevention tools work.
Other real-world research has found that babies given nirsevimab are 85% to 90% less likely to be hospitalized for RSV-related illness. The authors of the article wrote that nirsevimab may have been less effective in the new study because of differences in the way their study was designed. For example, the new study included older babies born before the beginning of the French immunization campaign, who could be expected to have lower risk of RSV-related hospitalizations.
Protection fades over time
The researchers found that nirsevimab, sold in the United States under the brand name Beyfortus, protected infants during their first respiratory season only.
That finding isn’t surprising, given that nirsevimab is known to provide protection for only five months, according to authors of the study, led by the French National Agency for Medicines and Health Products Safety and French National Health Insurance.
Like all antibodies, the antibodies in nirsevimab, known as monoclonal antibodies, don’t last forever, said Amesh Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security who was not involved with the new study.
But Adalja notes that other studies have suggested that nirsevimab provides at least partial protection during an infant’s second respiratory season.
“The evidence on durability is mixed,” Adalja said.
A warning sign or ‘statistical noise’?
An earlier French study[JW2] found that babies immunized with nirsevimab had fewer ear infections.
In the new study, however, researchers found that babies immunized with nirsevimab had a small increase in the risk of being hospitalized with ear, nose, and throat infections. The study authors cautioned, however, that that risk was based on a small number of cases, and doesn’t outweigh the benefits of RSV immunization.
The increased risk of ear infections also could be a fluke.
“It may just be statistical noise in the data,” Adalja said. “It doesn’t have biological plausibility.”
Vaccinating pregnant people keeps babies out of the hospital
The British study focused on an RSV vaccine given in pregnancy, which prompts the immune system to create protective antibodies that can be passed on to the fetus.
Babies whose moms were vaccinated during weeks 28 to 31 of pregnancy were 61% less likely to be hospitalized for RSV than infants whose mothers weren’t vaccinated, according to a study of 694 babies published online July 1 in The Lancet Child & Adolescent Health. None of the newborns in the study received nirsevimab.
Those findings are similar to earlier research about the effectiveness of RSV shots in pregnant women, said James Campbell, MD, a professor of pediatrics and interim head of the Division of Infectious Diseases and Tropical Pediatrics at the University of Maryland School of Medicine. He wasn’t involved in the study.
Antibodies fade with time
Protection against RSV varied with the age of the baby. The youngest infants receiving the greatest benefit, likely because the antibodies tend to decline over time, Adalja said.
Although babies of vaccinated moms were 61% less likely to be hospitalized for RSV in the first six months of life, newborns under 3 months of age were 76% less likely, according to the study.
Pregnant study participants were vaccinated against RSV during weeks 28 to 31 of pregnancy. A typical pregnancy lasts 40 weeks.
All babies in the UK study, which was conducted from September 2025 to January 2026, were born after at least 28 weeks of pregnancy. Infants born before 37 weeks are considered premature; babies born from 28 to 32 weeks are considered very preterm. Babies born prematurely or very prematurely have higher risks for multiple health problems.
The study’s findings are in line with earlier real-world research. In those studies, babies whose moms are vaccinated at least two weeks before delivery were 58% to 82% less likely to be hospitalized for RSV, according to background material in the new article.
Studies confirm the importance of immunizing infants
“These two studies are real-world confirmations that current infant RSV prevention tools work,” Adalja said. “Both tools deliver strong protection during the window they’re designed to cover.”
The new studies present a very different picture of vaccines than given by President Donald Trump, who this week repeated long-debunked claims about immunizations and autism. Trump issued an executive order that aims to make RSV immunizations available only to babies at high risk.
Executive orders from the president are akin to all-staff memos from a company CEO. While they provide marching orders to people who work for the Trump administration, they have no legal bearing on doctors, medical organizations, or states.
Current immunization recommendations from US health organizations haven’t changed.
The American College of Obstetricians and Gynecologists recommends vaccinating pregnant people against RSV from weeks 32 to 36 of pregnancy.
The American Academy of Pediatrics (AAP) recommends that all infants whose moms weren’t vaccinated against RSV receive either nirsevimab or a newer drug, clesrovimab, before the age of 8 months, during or before their first RSV season. Children at high risk should be vaccinated again before their second RSV season, up to19 months of age, according to the AAP.
“These are both significant technologies that will change the paradigm of pediatric RSV—if they’re used,” Adalja said.