Respiratory Syncytial Virus (RSV) is a common seasonal illness affecting the lungs and respiratory tract. While often presenting as a mild cold in healthy adults, it is a significant cause of serious lower respiratory tract infections, such as bronchiolitis and pneumonia, in infants and older adults. The virus circulates during annual epidemics, usually beginning in the fall and peaking in the winter months. A common concern is whether an infection early in the season provides lasting protection, or if it is possible to contract RSV again before the season ends.
The Nature of RSV Immunity
The short answer to the question of re-infection is yes, it is entirely possible to get RSV twice within the same season. Immunity following a natural RSV infection is often incomplete and short-lived, failing to provide the long-lasting protection seen with other viral diseases. This partial immunity is why most children are infected multiple times throughout early childhood and why adults can be re-infected throughout their lives.
Protective antibody levels against RSV may begin to decline within a few months of the initial infection. For adults, immunity can last anywhere from two to eight months, which is often shorter than the length of a typical RSV season. The virus itself is relatively stable and does not mutate rapidly like influenza, meaning re-infection is generally not due to encountering a completely new strain. Instead, the immune response is not robust enough to generate long-term memory cells. Subsequent infections are typically milder than the first.
Distinguishing Between Re-Infection and Prolonged Illness
When a person experiences a second bout of respiratory symptoms shortly after recovering from RSV, it can be difficult to determine if it is a true re-infection or simply a prolonged illness. The symptoms of RSV, particularly a cough and fatigue, can linger for weeks even after the virus is cleared from the body. This drawn-out recovery can be mistaken for a new infection.
A true re-infection means the person fully cleared the virus and then contracted it again after a new exposure. What seems like a second illness could also be the original infection persisting, or a secondary bacterial infection, such as pneumonia, occurring after the virus weakens the respiratory system. Clinicians may use tests, such as a real-time reverse transcriptase-polymerase chain reaction (rRT-PCR), to confirm if the current illness is a new viral exposure.
Populations Vulnerable to Repeated Severe Infection
While most healthy adults and older children experience mild, cold-like symptoms upon re-infection, specific demographic groups face a higher risk of severe disease or hospitalization from repeated RSV exposure. Infants under six months of age are at the highest risk for severe outcomes, especially those born prematurely or who have chronic lung disease. Children under two years old with congenital heart disease are also vulnerable to severe complications.
The elderly population (over age 65) and individuals with compromised immune systems or underlying heart or lung conditions face an increased likelihood of the virus progressing to a lower respiratory tract infection. For these individuals, a second infection in the same season, though less common, can be serious.
Strategies for Minimizing Seasonal Exposure
Several actionable strategies can significantly reduce the likelihood of contracting RSV, especially after a recent infection. Non-pharmaceutical interventions involve maintaining diligent personal hygiene, such as frequent hand washing with soap and water for at least 20 seconds. Cleaning and disinfecting frequently touched surfaces can also help limit the spread of the highly contagious virus.
In recent years, pharmaceutical options have become available to provide protection to high-risk groups. For adults aged 60 and older, and those aged 50–74 with elevated risk factors, the Centers for Disease Control and Prevention (CDC) recommends a single dose of an RSV vaccine.
For infants, protection can be provided either through a maternal RSV vaccine given to the pregnant parent between weeks 32 and 36 of gestation, or through a long-acting monoclonal antibody product administered to the infant. The long-acting monoclonal antibody, such as nirsevimab, provides passive immunity by directly supplying protective antibodies to the infant, offering protection for approximately five months. This passive immunization is recommended for all infants under eight months old entering or born during their first RSV season. These preventive measures are designed to reduce the risk of severe illness and hospitalization.