The Tdap (Tetanus, Diphtheria, and Pertussis) vaccine is an important tool in prenatal care, but it does not protect infants against Respiratory Syncytial Virus (RSV). Tdap targets bacterial diseases, while RSV is a virus. The Tdap shot is recommended during pregnancy primarily to safeguard the newborn against whooping cough, a serious bacterial infection. Preventing severe RSV disease requires specific, recently developed medical interventions. Both RSV and pertussis are significant concerns for newborns, which is why pregnant individuals are advised to seek protection against both.
The Purpose of the Tdap Vaccine
The Tdap vaccine protects against tetanus, diphtheria, and pertussis (whooping cough). Tetanus and diphtheria are caused by bacterial toxins, while pertussis is a highly contagious respiratory illness caused by the bacterium Bordetella pertussis. The vaccine contains inactivated toxins (toxoids) for tetanus and diphtheria, along with purified components of the pertussis bacteria.
The primary reason for administering Tdap during the third trimester of pregnancy is to prevent severe pertussis in the newborn. The pregnant individual’s immune system creates protective antibodies that cross the placenta, providing the baby with passive immunity at birth.
The recommended timing is between 27 and 36 weeks of gestation to allow for maximum antibody transfer before delivery. This passive protection is important because infants cannot begin their own pertussis vaccination series (DTaP) until they are two months old. Maternal Tdap vaccination can prevent more than 90% of pertussis cases in infants younger than two months.
Why RSV Poses a Threat to Infants
Respiratory Syncytial Virus (RSV) is a common, contagious virus that infects the lungs and respiratory tract. While most older children and adults experience a mild, cold-like illness, RSV is a major concern for infants, especially those under six months, due to their small airways.
The infection can quickly progress to lower respiratory tract diseases. These include bronchiolitis (inflammation of the small airways) and pneumonia, making RSV the most common cause of both conditions in babies. Subtle symptoms in young infants can include irritability, decreased activity, or brief pauses in breathing (apnea).
In the United States, RSV causes an estimated 58,000 to 80,000 hospitalizations annually among children younger than five years old. Infants born prematurely or those with chronic lung or congenital heart conditions face the highest risk of severe illness. This severity highlights the need for dedicated prevention methods.
Current Medical Strategies for RSV Prevention
Since Tdap does not protect against RSV, medical science uses specific, targeted methods to safeguard infants. These strategies provide the baby with antibodies to fight the virus, either generated in the mother or administered directly to the infant. The goal is to ensure protection during the first RSV season, which occurs during the fall and winter months.
Maternal RSV Vaccination
One approach is maternal RSV vaccination, which targets the RSV virus similarly to the Tdap mechanism. The RSVPreF vaccine (Abrysvo) is recommended for pregnant individuals between 32 and 36 weeks of gestation.
This vaccine stimulates the mother’s immune system to produce antibodies against the virus’s prefusion F protein. These antibodies pass across the placenta, providing the infant with passive protection that significantly reduces the risk of severe RSV disease for up to six months.
Monoclonal Antibody Products
A second strategy uses monoclonal antibody products, which are ready-made infection-fighting proteins, not vaccines. These antibodies are administered directly to the infant for immediate, temporary protection. The newest product, nirsevimab (Beyfortus), is a long-acting monoclonal antibody recommended for all infants under eight months entering their first RSV season.
Nirsevimab is a single-dose injection that provides season-long protection, lasting about five months, by binding to the RSV F protein and blocking viral replication. This single-dose formulation is an advancement over the older monoclonal antibody, palivizumab (Synagis), which required monthly injections throughout the RSV season. Palivizumab is generally reserved for a small subset of extremely high-risk infants, such as those with certain heart or lung conditions.
Most infants require protection through only one method: either the maternal vaccine or the infant monoclonal antibody. Health organizations recommend that infants receive nirsevimab if their mother did not receive the maternal RSV vaccine at least 14 days before delivery. This dual-approach system ensures almost all newborns are protected against severe RSV during their most vulnerable period.