Respiratory Syncytial Virus (RSV) is a highly common respiratory infection, affecting nearly every child before their second birthday. This virus causes infections of the respiratory tract, ranging from mild cold-like symptoms to severe conditions like bronchiolitis and pneumonia, particularly in infants. The severity of the initial illness often leads parents to question whether their child can catch the virus again. An RSV infection does not grant lifelong protection, making reinfection a frequent occurrence throughout a person’s life.
Why Reinfection Is Common
The human body’s immune response to an initial RSV infection is often short-lived and incomplete, which explains why children can contract the virus multiple times. Unlike infections such as measles, which provide robust, lasting immunity, the protection generated against RSV tends to wane quickly, sometimes within a few months. This partial immunity is insufficient to completely block the virus upon re-exposure.
The vulnerability to reinfection lies in the nature of the immune memory generated. The initial infection often fails to establish a strong enough cellular or humoral immune response to generate protective memory lymphocytes. Furthermore, the virus exists as two major subtypes, A and B, with different strains, meaning immunity against one strain may not fully protect against another. Local immune defenses, specifically antibodies in the nasal passages, are poor at maintaining a long-term protective response against RSV, allowing the virus to re-establish an infection.
What Second and Subsequent Infections Look Like
Subsequent infections are generally less severe than the primary episode, especially in older, healthy children. The first encounter with RSV is often the most serious, with approximately 40% of first-time infections causing a lower respiratory tract illness, such as bronchiolitis. After the first infection, the immune system retains memory that helps it fight the virus more effectively the next time, leading to milder symptoms that often resemble a common cold.
The severity of reinfection depends significantly on a child’s underlying health and age. Infants who experience their first RSV infection early, particularly before six months of age, are more likely to have a subsequent hospital-attended reinfection. Even a mild reinfection can be serious for children with pre-existing conditions, such as chronic lung disease, congenital heart defects, or those born prematurely. These high-risk groups may experience significant lower respiratory tract symptoms, requiring hospitalization and supportive care.
Protecting Children from Repeated Exposure
Parents can implement measures to limit a child’s exposure to the virus, which is transmitted through respiratory droplets and contact with contaminated surfaces. Consistent hand washing with soap and water for at least 20 seconds is a highly effective way to reduce transmission. It is also helpful to routinely clean high-touch surfaces and to avoid close contact with anyone showing cold or flu-like symptoms.
In addition to hygiene practices, certain children may be eligible for prophylactic measures to prevent severe disease. For infants at high risk for severe illness, such as those born prematurely, a monthly injection of the monoclonal antibody palivizumab (Synagis) may be recommended during the RSV season. A newer, long-acting monoclonal antibody, nirsevimab (Beyfortus), offers a single injection that can protect a broader population of infants through their first RSV season. Pediatricians determine which preventative option is appropriate for a child based on their age and specific risk factors.