Respiratory syncytial virus, commonly known as RSV, is a widespread respiratory virus. In Hong Kong, RSV infections can occur throughout the year rather than only during the winter months. The virus spreads through respiratory droplets and nasal secretions, as well as through contaminated hands, toys and other objects.
For most healthy adults, RSV causes cold-like symptoms such as a runny nose, cough, fever and tiredness. Pregnant women do not necessarily develop severe illness after infection. However, pregnancy-related changes in the body, together with the need to care for young children at home, may increase the chance of coming into contact with the virus. After birth, a baby may become infected through close contact with an infected caregiver. At the same time, antibodies produced by the mother during pregnancy can cross the placenta and provide the baby with some protection during the early months of life.
Why are babies particularly vulnerable?
RSV is a common cause of bronchiolitis and pneumonia in infants under one year of age. A baby’s airways are narrow and the immune system is still developing. Infants younger than six months, premature babies, and babies with congenital heart disease or chronic lung disease are more likely to develop severe illness.
Early symptoms may include a blocked or runny nose, cough, fever and reduced appetite. Some babies may show less obvious signs, such as drinking less milk, appearing unusually tired or breathing faster than usual. In more serious cases, RSV can cause breathing difficulties, low oxygen levels and dehydration, and hospital treatment may be required.
Parents should seek urgent medical attention if a baby develops bluish lips or skin, chest retractions when breathing, flaring of the nostrils, persistent wheezing, unusual drowsiness, difficulty feeding or a significant reduction in wet nappies. Do not rely solely on over-the-counter fever medicine or use antibiotics without medical advice. Antibiotics do not treat RSV itself.
RSV vaccination options for pregnant women in Hong Kong
There are two main ways to protect an infant from severe RSV: vaccination during pregnancy or administration of a long-acting monoclonal antibody to the baby after birth. Most babies do not need both. The appropriate option depends on factors such as the stage of pregnancy, the expected delivery date, the baby’s health and local availability. A pregnant woman should discuss the options with her obstetrician or the baby’s paediatrician.
Option 1: Maternal RSV vaccination. Overseas guidance commonly uses Pfizer’s Abrysvo as a single dose during weeks 32 to 36 of pregnancy. The vaccine helps the mother produce antibodies, which can cross the placenta and protect the baby after birth. Clinical studies have shown that maternal vaccination can reduce the risk of severe RSV lower respiratory tract disease and RSV-related hospitalisation in young infants.
However, under the current local consensus in Hong Kong, universal RSV vaccination for all pregnant women is not recommended at this stage. A pregnant woman should consult her obstetrician about whether the vaccine is available at the appropriate stage of pregnancy, whether she has any allergy or other contraindications, and how the potential benefits and risks apply to her situation. The decision should be made after receiving clear information and giving informed consent.
Option 2: Nirsevimab after birth. Nirsevimab is a long-acting monoclonal antibody, not a conventional vaccine. It provides ready-made antibodies directly to the baby, so protection does not depend on the baby developing its own immune response. A single injection may provide protection for approximately five months and may be considered for babies who did not receive protection through maternal vaccination or who have a higher risk of severe disease.
Some healthcare institutions in Hong Kong provide nirsevimab services. This does not mean that Hong Kong has introduced a universal, free infant immunisation programme. Parents should consult a paediatrician about eligibility, availability, dosage and cost. If the mother received an RSV vaccine during the current pregnancy as advised by her doctor, the baby will generally not need both maternal vaccination and nirsevimab unless the doctor recommends otherwise.
Treatment and everyday prevention
There is currently no specific routine treatment that eliminates RSV. Management is mainly supportive. This may include maintaining fluid intake, clearing nasal secretions, and monitoring the baby’s breathing and feeding. Severe cases may require oxygen, intravenous fluids or tube feeding. Antibiotics are used only when a doctor identifies a bacterial complication; they do not work against RSV.
If a pregnant woman or family member develops respiratory symptoms, they should wear a surgical mask, rest at home and avoid kissing or having close contact with a young baby. Caregivers should wash their hands with soap and water for at least 20 seconds before and after handling the baby. Frequently touched surfaces and toys should be cleaned, indoor spaces should be well ventilated, and towels and eating utensils should not be shared. People who are unwell should not visit a newborn.
In summary, RSV is usually mild in healthy pregnant women, but it can cause serious respiratory disease in newborns and young infants. Families should not ask only whether they should “get the injection”. They should consider the stage of pregnancy, the expected delivery date, the baby’s risk factors and the advice of a local healthcare professional when choosing between maternal vaccination and infant monoclonal antibody protection. A qualified healthcare should assess all vaccination and antibody decisions professional. See more.
