From the Guidelines
The RSV vaccine given during pregnancy is highly effective in protecting newborns against respiratory syncytial virus infection, with the CDC recommending a single dose of the RSVpreF vaccine for pregnant women during weeks 32 through 36 of pregnancy 1. The maternal RSV vaccine (Abrysvo) reduces the risk of severe RSV disease in infants, working through the transfer of maternal antibodies across the placenta to the developing baby. Key points to consider when administering the RSV vaccine during pregnancy include:
- The vaccine is administered as a single 0.5 mL intramuscular dose during 32 through 36 weeks’ gestation 1
- The vaccine contains stabilized prefusion F glycoproteins from RSV A and RSV B 1
- Available data indicate that the benefit of vaccination in preventing RSV-associated lower respiratory tract infection in infants outweighs risks, including the potential risk for preterm birth and hypertensive disorders of pregnancy 1
- The CDC recommends either maternal RSVpreF vaccination during pregnancy or nirsevimab administration to the infant to prevent RSV-associated lower respiratory tract infection in infants, but both are not needed for most infants 1 The RSV vaccine is safe for both mother and baby, with the most common side effects being injection site pain, headache, muscle pain, and fatigue. This vaccination strategy is particularly important because RSV can cause serious respiratory illness in young infants, including bronchiolitis and pneumonia, and newborns don't yet have fully developed immune systems to fight off the infection effectively 1. By getting vaccinated during pregnancy, mothers provide their babies with immediate protection from birth when they are most vulnerable to severe RSV disease.
From the Research
Effectiveness of RSV Vaccine during Pregnancy
- The RSV vaccine has been shown to be effective in reducing laboratory-confirmed RSV hospitalizations in infants when administered to pregnant women 2.
- A study found that maternal RSV vaccination compared with placebo reduces infant hospitalization with laboratory-confirmed RSV disease (risk ratio 0.50,95% confidence interval 0.31 to 0.82) 2.
- The vaccine has also been found to have little or no effect on the risk of congenital abnormalities, intrauterine growth restriction, and stillbirth 2.
Safety of RSV Vaccine during Pregnancy
- The safety of the RSV vaccine during pregnancy has been evaluated, and it has been found to have little or no effect on the risk of maternal death and infant death 2.
- However, there may be a safety signal warranting further investigation related to preterm birth, although the evidence is very uncertain 2.
- A study found that pregnant women generally welcome and prefer maternal RSV vaccination over other strategies, but have concerns about vaccine safety and effectiveness 3.
Mechanism of RSV Vaccine
- The RSV vaccine works by inducing antibodies against the RSV F and G proteins, which are important for the virus's entry into host cells 4, 5.
- A study found that antibodies specific for antigenic site Ø on the pre-F protein are more efficacious at preventing RSV infection than antibodies specific for antigenic site II 4.
- The use of virus-like particles (VLPs) as a vaccine platform has been explored, and has been shown to induce immune responses against RSV in mice 5.