In recent years, respiratory syncytial virus (RSV) has frequently broken out in Hong Kong. Once newborns are infected, it can easily lead to severe pneumonia or bronchiolitis. Therefore, the medical community has launched an RSV vaccine specifically for pregnant women, allowing antibodies to be transferred to the fetus through the placenta, building the first line of defense for health after birth.
However, "Is it safe for pregnant women to get the RSV vaccine? Is it worth it?" is a common question among many expectant mothers. This article will break down the true nature of the RSV virus and the current infection situation in Hong Kong, and comprehensively analyze the pros and cons of pregnant women getting vaccinated, so that we can make the most reassuring decision for your baby's health!
Key points summary of RSV vaccine for pregnant women
- Virus threat：RSV is highly contagious and is the leading cause of severe pneumonia and bronchiolitis in infants under one year old in Hong Kong, even requiring emergency hospitalization for oxygen.
- Protection mechanism：The vaccine does not contain live viruses. After pregnant women are vaccinated, their bodies produce specific neutralizing antibodies, which are then transferred to the fetus through the placenta, providing passive immunity to infants with zero immunity.
- Protective effectThe vaccine can perfectly cover the most vulnerable golden growth period for infants, significantly reducing the risk of severe lower respiratory tract diseases and hospitalization within the first 90 days after birth by up to approximately 81.8%, with protection lasting for nearly 6 months.
- Golden opportunityInternational authoritative institutions strictly guide that it must be administered between the 32nd and 36th week of pregnancy to ensure sufficient time for antibody transfer and effectively avoid any potential risk of premature birth.
- Security assessmentThe overall safety of the vaccine is consistently recognized by institutions such as the U.S. FDA. Common side effects are limited to mild, temporary fatigue or redness and swelling at the injection site. When vaccination specifications are strictly followed, it is very safe for both pregnant women and fetuses.
What is the RSV virus? Why do pregnant women need to pay special attention to it?
For adults, infection with RSV might feel like just a common cold; however, for newborns, it can be a potentially fatal threat. Understanding the characteristics of this virus is the first step for expecting parents to prepare their infants for defense.
How does the RSV virus spread?
RSV is an extremely common and highly contagious virus that can cause various respiratory illnesses. It is highly transmissible and is primarily spread through the following two routes:
- Droplet transmission：When an infected person coughs, sneezes, or talks, droplets containing the virus spread through the air and are inhaled by people nearby.
- Contact transmissionViruses can survive on hands and hard surfaces for several hours. If you touch these contaminated surfaces and then touch your eyes, nose, or mouth, you can become infected.
What are the health risks of RSV for newborn infants?
Newborn infants have immature immune systems and underdeveloped airways. Once infected with RSV, their condition is often much more severe than in adults:
- Cause severe lower respiratory tract infectionRSV is the leading cause of bronchiolitis and pneumonia in infants under one year of age.
- Dangerous complicationsViruses can cause inflammation and swelling of a baby's delicate trachea, leading to excessive mucus production. This can result in persistent high fever, severe cough, wheezing, rapid breathing, and even apnea.
- High hospitalization rateMany infected infants experience dehydration due to difficulty breathing and inability to feed, requiring hospitalization for oxygen therapy or intravenous fluids.
How serious is the current RSV outbreak in Hong Kong?
What is the proportion of infant and child hospitalizations and severe cases?
本港5歲以下兒童每年的RSV相關住院率高達每10萬人有900至1,300宗；其中一歲以下的嬰兒更是最高危群體，佔了整體RSV兒童住院病例的45%至55%。部分病情嚴重的嬰兒會出現缺氧、呼吸衰竭或無法進食，需要緊急入院接受氧氣治療或靜脈輸液；更有約1.5%至2.4%的RSV住院病童需要入住兒童深切治療部。¹
Does RSV have a distinct seasonal peak?
In Hong Kong, RSV infections occur year-round, but according to epidemiological data from the Centre for Health Protection, there is usually a more prominent peak of infections in the spring and summer months (approximately March to August).²
What are the recommendations from the Centre for Health Protection?
Facing the highly contagious RSV, the Centre for Health Protection and local pediatric specialists have been closely monitoring the community infection situation and offer the following protective advice:
- Strict daily hygieneParents and caregivers must maintain good personal and environmental hygiene at all times. Hands must be thoroughly cleaned before touching infants.
- Reduce visits to crowded places.During RSV season, try to avoid taking newborns to crowded public places with poor ventilation.
- Learn about preventive medicine options earlyExperts recommend that expectant mothers planning a pregnancy or who are pregnant should proactively inquire with their obstetrician about the latest preventive vaccine information.
What is the RSV vaccine for pregnant women? How does it provide protection?
How are antibodies produced after maternal vaccination?
When pregnant women are vaccinated, the trace antigens in the vaccine stimulate the mother's immune system. After the mother's body identifies these antigens, it actively produces "specific neutralizing antibodies" against the RSV virus. This antibody production process takes approximately 2 to 4 weeks to reach peak levels of antibodies in the mother's body, sufficient to combat the actual virus.
How are antibodies transferred to the fetus through the placenta?
During the mid to late stages of pregnancy, the placenta is not only a bridge for nutrient transport but also a superhighway for transmitting antibodies. RSV antibodies from the mother's body pass through the placenta and continuously enter the fetus's circulatory system.
To ensure the most ample time for antibody transfer before the fetus is born, the medical community and pharmaceutical companies generally recommend that expectant mothers get vaccinated between the 32nd and 36th weeks of pregnancy. This way, the baby will have their own protective shield from the moment they are born, possessing the ability to resist RSV infection immediately.
How long is the protection period for newborns?
孕婦接種疫苗能為出生首90天的嬰兒提供高達81.8%的保護力，大幅降低因RSV引起嚴重下呼吸道疾病及需要住院的風險。即使到了嬰兒出生後180天，疫苗預防重症的有效率依然能維持在接近69.4%的高水平。³
Benefits of getting the RSV vaccine during pregnancy?
Can the risk of severe infection after birth be reduced?
After pregnant women receive the RSV vaccine, they can build a strong first line of defense for newborns. Even if the infant unfortunately comes into contact with the virus, antibodies passed on from the mother can help suppress viral replication, greatly reducing the severity of the illness and preventing it from worsening into a severe case.
Is it possible to reduce the chance of hospitalization within the first 6 months?
The first 6 months after a baby's birth are a critical period when their trachea is narrowest and their immunity is weakest. This age group is also at high risk of hospitalization due to RSV infection. After pregnant women are vaccinated, antibodies from their bodies provide protection that lasts through these crucial 6 months. This significantly reduces the likelihood of infants requiring emergency hospitalization for respiratory distress, hypoxia, or an inability to feed, as well as the need for oxygen therapy, intubation for suctioning, or admission to the pediatric intensive care unit.
Which babies can get the most protection?
Although all full-term infants vaccinated by their mothers benefit, the following categories of infants receive particularly significant protective benefits:
- 在RSVBaby born during peak hoursThey are born into an environment with high viral activity, and their innate antibodies are immediately effective.
- Baby with older siblings at homeIf babies have older siblings attending kindergarten or elementary school, they can easily bring the RSV virus home from school, causing cross-infection. Vaccines can provide crucial protection for the most vulnerable newborns in the home.
- Babies admitted to daycare early：Daycare centers are a major area of concern for RSV outbreaks. If infants need to enter a childcare setting at a few months old, maternal antibodies can significantly reduce their risk of severe illness from cluster infections.
When should pregnant women get the RSV vaccine?
Currently, international authoritative health organizations, such as the U.S. FDA and CDC, have strict guidelines on the timing of RSV vaccination for pregnant women.
Why is it recommended to vaccinate between 32-36 weeks?
It takes about 14 days after a pregnant woman receives a vaccination for her body to produce sufficient high levels of antibodies and transfer them to the fetus. Vaccinating between 32 and 36 weeks ensures that even if the baby is born full-term at 38 or 39 weeks, the mother will have had the most ample time to complete antibody transfer.
Why is the third trimester considered ideal?
During the third trimester, the placenta reaches its peak functionality, actively pumping RSV antibodies from the mother's blood into the fetus. This ensures that the antibody concentration in the fetus reaches its apex at the moment of birth, seamlessly preparing it to face potential viral threats after leaving the womb.
Does getting vaccinated too early or too late have any impact?
If the injection is given too early, antibody levels in the mother's body may begin to decline before the fetus is born, leading to insufficient protection for the infant after birth to cover the high-risk period of the first 6 months. Conversely, if the injection is rushed a few days before delivery, the pregnant woman's body will not have enough time to produce and transfer sufficient antibodies. As a result, the infant will be born with insufficient antibodies in their body, rendering the vaccine's protective effect a waste.
What are the risks for pregnant women getting the RSV vaccine?
Is the risk of premature birth increased?
Clinical trials showed a very slight increase in the rate of premature births (5.7%) in the vaccinated group compared to the unvaccinated group (4.7%), which could not be confirmed to be directly caused by the vaccine.⁴ To eliminate any potential risks, the US FDA and CDC strictly regulate that pregnant women can only be vaccinated between the 32nd and 36th week of pregnancy. This is because the fetus is more mature at this later stage, and even if premature labor occurs, the health risks associated with severe premature birth can be significantly reduced.
Common side effects during pregnancy include: nausea, fatigue, frequent urination, breast tenderness, and mood swings.
Pregnant women may experience some mild, temporary reactions when their immune system activates to produce antibodies after receiving the RSV vaccine. These are normal physiological responses and usually resolve on their own within 1 to 2 days:
- Local reactionRedness, swelling, pain, or muscle soreness at the injection site.
- Systemic reactionMild headache, fatigue, muscle or joint pain. A small number of pregnant women may experience mild nausea.
Is Guillain-Barré syndrome (GBS) common?
Guillain-Barré syndrome (GBS) is a very rare autoimmune neurological disease. Rumors sometimes circulate about vaccines potentially triggering GBS. In fact, no cases of pregnant women contracting GBS were observed in clinical trials for RSV vaccines involving pregnant women. Health authorities worldwide are also continuously and closely monitoring vaccines after they are on the market. Based on current data, the probability of GBS being triggered by vaccination is extremely low, and expectant mothers do not need to be overly alarmed.
Overall safety analysis
In summary, the currently approved RSV vaccine for pregnant women is a recombinant protein vaccine. It does not contain live viruses, meaning there are no live RSV viruses in the vaccine, and it absolutely cannot cause RSV infection in pregnant women or their fetuses.
Additionally, the RSV vaccine for pregnant women has received recognition from multiple international authorities, including the US FDA, CDC, and obstetrics and gynecology associations from various countries. They unanimously acknowledge the overall safety and effectiveness of the RSV vaccine for pregnant women. The immense protective benefits it provides to newborns far outweigh the potential risks observed in clinical settings.
How to decide whether to get the RSV vaccine for pregnant women?
1. Assess the estimated due date and RSV peak season
If your due date falls within this high-risk season, or the first 6 months after your baby is born, which are the most vulnerable, will span this peak period, then the protective benefits of vaccination will be maximized. Maternal antibodies will ensure your baby has timely protection when viruses are most prevalent in the community.
2. Examine the home environment and potential sources of infection
If there are older siblings at home, they can easily get RSV at school and unintentionally bring it home. For such families, getting newborns, who have no immunity, vaccinated in advance is definitely a wise move.
3. Own pregnancy status and risk of preterm birth
If you have a high-risk pregnancy, a history of premature birth, or are currently carrying multiple babies, be sure to inform your obstetrician honestly. Your doctor will assess your overall risk and use their professional judgment to determine if you are suitable for vaccination during the optimal window between 32 and 36 weeks.
Can babies or children get the RSV vaccine?
In current medical development, there are no traditional RSV vaccines on the market that can be directly administered to infants or children. This is precisely why the medical community highly values and strongly recommends that expectant mothers receive the maternal RSV vaccine during pregnancy. By generating antibodies in the mother and transferring them to the fetus through the placenta, it is currently the most direct and effective method to provide immune protection to newborns.
If parents have any questions about RSV prevention options for their infants and young children, it is recommended that they consult a pediatrician as soon as possible to develop the most suitable health protection plan for their baby.
Quick Answers to Common Questions About RSV Vaccination for Pregnant Women
How long do antibodies from the RSV vaccine for pregnant women last?
After pregnant women are vaccinated during pregnancy, the antibodies produced by their bodies are transferred to the fetus through the placenta. After birth, this maternal protection provides strong defense for up to 6 months. These 6 months are a high-risk period when newborns' tracheas are narrowest and most susceptible to severe illness from infection.
Where can pregnant women get the RSV vaccine?
Currently, the RSV vaccine for pregnant women is not included in the free routine vaccination program at the Maternal and Child Health Centres of the Department of Health in Hong Kong. Therefore, expectant mothers who wish to get vaccinated will need to make an appointment and pay for it themselves at private hospitals, specialist clinics, or private medical institutions. It is recommended to discuss this with your obstetrician during your prenatal check-ups, assess your physical condition, and then arrange for vaccination.
When can pregnant women get the RSV vaccine?
International authoritative medical organizations, including the U.S. FDA and CDC, have very strict guidelines, recommending that pregnant women must get vaccinated during the golden period between the 32nd and 36th week of pregnancy.
Reference materials:
- Hong Kong Med JEpidemiology of respiratory syncytial virus infection and its effect on children with heart disease in Hong Kong: a multicenter review
- Centre for Health Protection, Department of HealthRespiratory syncytial virus infection
- The New England Journal of Medicine (NEJM)Bivalent Prefusion F Vaccine in Pregnancy to Prevent RSV Illness in Infants
- US Food and Drug Administration (FDA)FDA Approves First Vaccine for Pregnant Individuals to Prevent RSV in Infants