RSV Prevention: A New Monoclonal Antibody for Infants and Children

• In the first two years of life, 90% of children contract RSV at least once, and more than 50% of those infected require hospitalization. Some cases are severe, requiring ICU admission and ventilatory support.
• RSV is one of the top three causes of pneumonia and bronchitis in children under five, which can be severe and life-threatening.
• RSV infection can now be prevented through passive immunization using monoclonal antibodies. This protection is available for newborns up to 2-year-olds, reducing the risk of infection by 79.5%, lowering hospitalization due to lower respiratory tract infections by 82.7%, and decreasing severe cases and ICU admissions by 75.3%.

Respiratory syncytial virus (RSV) is a highly common respiratory infection in children, with studies showing that 90% of children in their first two years of life contract RSV at least once. More than 50% of those infected require hospitalization for close medical monitoring, while some cases develop severe symptoms or complications. RSV spreads easily and rapidly, especially during the rainy and winter seasons when outbreaks occur. It is one of the leading causes of pneumonia- and bronchiolitis-related deaths in children under five, accounting for one-third of such cases. Severe RSV infections cause inflammation in the small airways of the lungs, leading to mucus buildup that blocks these airways. This obstruction can cause wheezing and prevent proper gas exchange in the lungs, resulting in insufficient oxygen levels. If RSV directly infects lung tissue, it can lead to viral pneumonia.

• Early symptoms resemble the common cold, including nasal congestion, coughing, and possible wheezing.
• Fever
• Decreased appetite
• Reduced activity and playfulness
• Increased irritability and fussiness
• Irregular breathing or temporary pauses in breathing

• Rapid and labored breathing
• Persistent coughing or wheezing
• Bluish discoloration around the lips or nails
• Flaring nostrils or chest retractions while breathing
• High fever above 38°C (especially in infants under three months old)

If any of these symptoms occur, seek immediate medical attention, especially for infants under one year old as their symptoms can be harder to detect due to their limited ability to communicate. If there is any concern or noticeable abnormality, take the child to a hospital promptly for evaluation and treatment to reduce the severity of the illness.

Preventing RSV infection and reducing severity with monoclonal antibody for RSV prevention (Nirsevimab)

The monoclonal antibody for RSV prevention is not a vaccine; it works to prevent infection through a process called passive immunization. Passive RSV immunization involves administering RSV-specific antibodies (Nirsevimab) to provide immediate protection against the virus. It is a safe and effective way to reduce the risk of infection and severe illness in children.

• Reduces the risk of RSV infection by 79.5%
• Lowers the risk of hospitalization due to RSV-related lower respiratory tract infections by 82.7%
• Decreases the severity of illness and reduces ICU admissions by 75.3%
• Provides protection against RSV infection for up to 5 months, covering the peak outbreak season.

Monoclonal antibody for RSV prevention (Nirsevimab) can be administered to children from birth to 2 years old. It can be given during the RSV season as the immunity develops immediately after injection. According to the recommendation of the Royal College of Pediatricians of Thailand, monoclonal antibody for RSV prevention (Nirsevimab) is advised as follows:

First Season

• Monoclonal antibody for RSV prevention (Nirsevimab) can be administered to all healthy newborns up to 12 months old.
• It is recommended for infants younger than 8 months and may be considered for infants aged 8-12 months.
• It is recommended for high-risk infants from birth to 12 months who are vulnerable to severe RSV infection. High-risk infants include:
  • Infants with chronic lung disease due to premature birth (BPD) who still require treatment with steroids, diuretics or oxygen within 6 months before RSV season
  • Children with severe immunodeficiency
  • Children with severe cystic fibrosis, such as those who have been hospitalized for lung disease exacerbation in their first year of life, have abnormalities on chest X-rays, or suffer from malnutrition (weight-for-length < 10th percentile)
  • Children with hemodynamically significant congenital heart disease for which they are still receiving treatment

Notes:

• It is recommended that the immunization be administered at the beginning of the RSV season, which occurs from June to October each year.
• For infants born during the RSV season, monoclonal antibody for RSV prevention (Nirsevimab) can be given immediately after birth.

Recommended dosage:

• Infants weighing less than 5 kg: 50 mg single intramuscular injection.
• Infants weighing more than 5 kg: 100 mg single intramuscular injection.

Second Season

• Monoclonal antibody for RSV prevention (Nirsevimab) can be administered to all healthy newborns aged 12–24 months.
• It is recommended for children aged 12–19 months who are at risk of severe RSV infection.
• It may be considered for children aged 19–24 months who are at risk of severe RSV infection.

Notes: The administration of monoclonal antibody for RSV prevention (Nirsevimab) depends on the child's weight and age. A pediatrician should always be consulted before receiving the immunization, and a doctor should assess the need for each case.

Recommended dosage: Monoclonal antibody for RSV prevention (Nirsevimab) should be administered at a dose of 200 mg (two 100 mg injections given simultaneously at two intramuscular sites).

Monoclonal antibody for RSV prevention (Nirsevimab) is highly safe, with minimal adverse effects. Side effects are rare and usually mild. The most common reactions include rashes (0.9% of cases), fever (0.5% of cases) and injection site reactions (0.3% of cases).

Contraindications

Monoclonal antibody for RSV prevention (Nirsevimab) should not be administered to children with a history of severe allergic reactions to Nirsevimab or its components, such as arginine or histidine.

• Supports long-term health, as even after recovering from RSV infection, long-term respiratory effects such as bronchial hyperreactivity, asthma, or impaired lung function may persist. Prevention and monitoring of RSV infection are crucial for both short-term and long-term child health.
• Reduces financial burden, including direct costs such as medical expenses and indirect costs such as parental absences from work to care for sick children.
• Helps lower healthcare costs, as RSV-related hospital expenses for children under five in Thailand amount to approximately 1.75 billion THB annually, with an average hospital stay of six days.

Notes:

• Passive RSV immunization is crucial for building immunity in newborns during their first year of life.
• Children from birth to 2 years old, including those with underlying conditions, are eligible for monoclonal antibody for RSV prevention (Nirsevimab).
• Monoclonal antibody for RSV prevention (Nirsevimab) can be administered alongside routine vaccinations, including live vaccines, without requiring spacing between doses, as it does not interfere with vaccine-induced immunity.
• Monoclonal antibody for RSV prevention (Nirsevimab) can be given simultaneously with other vaccines, administered at separate injection sites.