BANGKOK– As the rains ease and nights turn cooler, respiratory syncytial virus, or RSV, is circulating again in homes, nurseries, and playgrounds across Thailand. This common virus spreads through droplets from coughs and sneezes, and it hits infants and toddlers hardest.
The Royal College of Pediatricians of Thailand is urging families to consider Nirsevimab, sold as Beyfortus, a long-acting monoclonal antibody that offers up to six months of protection from a single injection.
RSV is a leading cause of lower respiratory tract infections in young children worldwide, and Thailand sees the same pattern. Almost all children meet the virus by their second birthday. For the youngest, especially those under six months or with conditions such as prematurity, a mild cold can worsen into bronchiolitis or pneumonia that needs hospital care.
Pediatric specialists report a predictable surge in admissions every rainy season, and they call prevention the best approach.
Recent data highlight the burden. From 2015 to 2020, a nationwide review found more than 19,340 RSV-related hospitalizations among Thai children under 18. Pneumonia made up 70.76 percent of cases, and bronchiolitis 14.73 percent.
Respiratory Syncytial Virus (RSV)
Infants under one year suffered the highest mortality, at 1.75 per 100,000 person-years, far above older age groups. In provinces such as Sa Kaeo and Nakhon Phanom, research shows one in 187 infants aged 1 to 11 months and one in 450 children aged 1 to 4 years are hospitalized each year with RSV pneumonia.
After the COVID-19 years, patterns shifted, with fewer cases during restrictions, then a strong rebound. Most infections now fall between July and October, accounting for 73.55 percent of cases. The economic strain is real. A single RSV episode costs families a median of 17,000 baht, around 539 US dollars, rising to 67,500 baht, about 2,112 US dollars, for hospital care. This pressure also extends to the universal healthcare system.
COVID-19 precautions temporarily muted RSV transmission. As daily life resumed, cases climbed again. In pre-pandemic Chiang Mai data from 2016 to 2019, 60 to 70 percent of hospitalized RSV patients were under 12 months, and 80 percent were under two years. Early symptoms such as cough, fever, and wheezing can progress to low oxygen levels and the need for intensive care. Risk is far higher in babies born preterm and in children with heart or lung disease.
Nirsevimab, or Beyfortus, sits at the centre of current guidance from the Royal College of Pediatricians of Thailand. Approved by Thailand’s Food and Drug Administration in 2023, this antibody targets the RSV fusion protein and blocks the virus from entering cells.
Compared with palivizumab, or Synagis, which requires monthly injections and costs far more, Beyfortus offers a simpler path. One intramuscular dose gives protection for at least five months, often up to six. Dosing is 50 mg for babies under 5 kg and 100 mg for those 5 kg or more, which fits the Thai rainy to cool season.
Reduction in Hospitalizations
Evidence supports its use. The MELODY trial of Nirsevimab and Beyfortus reported 74.5 percent efficacy against medically attended lower respiratory infections, and up to a 77 percent reduction in hospitalization risk in the 2024 to 2025 season.
Rollouts in the United States have shown fewer emergency visits and intensive care admissions. For Thai families, this can mean less time in the hospital and a smoother first year of life. Safety findings are reassuring.
Side effects such as rash or injection site tenderness occur in fewer than 1 in 10 recipients, and are usually mild. Beyfortus can be given alongside routine childhood vaccines.
Current recommendations, aligned with global advice from groups such as the CDC and WHO, focus on infants younger than eight months entering their first RSV season, and on high-risk children up to 24 months who may benefit from a second dose.
Timing matters. Babies born during the season can receive a dose at birth, and others can receive it before the season begins. If the mother received an RSV vaccine during pregnancy, clinicians can advise on how to combine that protection with infant dosing.
Basic measures still help. Regular handwashing, avoiding crowded settings during peak months, and keeping unwell siblings at home reduce spread. Even so, medicine offers the strongest shield. RSV causes an estimated 40,000 deaths in children globally each year, but targeted prevention can save lives in Thailand.
Parents are sharing positive experiences. Some report that Beyfortus kept their babies out of the hospital in the last season and gave them confidence during peak months. With pediatricians nationwide standing behind the guidance, this season offers a clear opportunity.
Want peace of mind before the next wave hits? Book a visit, ask about Beyfortus, and put RSV protection in place.
