The US Food and Drug Administration (FDA) has approved the first vaccine that protects newborns from respiratory syncytial virus (RSV), a common and potentially serious respiratory infection. The vaccine, made by Pfizer, is given to pregnant women late in their pregnancies and provides protection to infants through their first six months of life.
What is RSV and why is it dangerous?
RSV is a virus that causes cold-like symptoms such as runny nose, cough, fever, and wheezing. However, in some cases, it can lead to more severe complications such as bronchiolitis, pneumonia, and respiratory failure. RSV is the leading cause of hospitalization in infants under a year old in the US every year, and it can also affect older adults and people with weakened immune systems.
According to the CDC, RSV causes about 58,000 hospitalizations and 100 to 500 deaths among children younger than 5 years old each year in the US. It also causes about 177,000 hospitalizations and 14,000 deaths among adults 65 years and older each year in the US.
There is no specific treatment for RSV infection, and prevention is the best way to protect against it. However, until now, there was no vaccine available for RSV.
How does the new vaccine work?
The new vaccine, named Abrysvo, is not a traditional vaccine that stimulates the body’s immune system to produce antibodies against the virus. Instead, it is a form of passive immunity that provides ready-made antibodies that can bind to the virus and block it from infecting healthy cells.
The vaccine is given as a single injection to pregnant women between 32 and 36 weeks of gestation. The antibodies are then transferred from the mother to the fetus through the placenta and provide protection to the newborn for up to six months after birth. The vaccine can also be given as a second dose to infants up to 24 months of age who remain at high risk of severe RSV disease through their second RSV season.
What are the benefits and risks of the new vaccine?
In a trial of more than 7,000 pregnant women and their infants, the vaccine reduced the risk of severe RSV disease by 82% and the risk of RSV-related doctor visits by 57% in the first three months after birth. By six months after birth, the vaccine reduced the risk of severe RSV disease by 69% and the risk of RSV-related doctor visits by 51%. After about six months, the vaccine’s effectiveness wore off and was similar to a placebo.
The most common side effects of the vaccine were injection site reactions, headache, fatigue, muscle pain, nausea, and fever. The FDA also noted that there was a slightly higher proportion of preterm births in babies whose mothers received the vaccine compared to those who received a placebo: 5.7% vs. 4.7%, respectively. However, the agency said that this difference was not statistically significant and that further studies are needed to confirm the safety of the vaccine in this regard.
The FDA’s approval of Abrysvo was based on the recommendation of its independent vaccine advisers, who voted unanimously in favor of its effectiveness and safety in May. The CDC’s Advisory Committee on Immunization Practices (ACIP) will also review the vaccine and issue its recommendations on its use.
What are the implications of the new vaccine?
The approval of Abrysvo marks a major milestone in the fight against RSV, which has been a public health challenge for decades. Pfizer estimates that if the vaccine were universally applied, it could prevent up to 16,000 hospitalizations and more than 300,000 doctor visits due to RSV each year in the US.
However, the vaccine does not provide long-term protection and does not cover all infants at risk of RSV infection. Therefore, other preventive measures such as hand washing, avoiding contact with sick people, and covering coughs and sneezes are still important to reduce the spread of RSV.
Moreover, Abrysvo is not the only option available to protect infants from RSV. In July, the FDA approved another antibody product called Beyfortus (nirsevimab), which can be given as a single injection to all infants after birth and lasts for four to six months. Beyfortus is also made by Pfizer in collaboration with AstraZeneca.
Additionally, there are several other vaccines and antibodies in development for different age groups and populations at risk of RSV infection. For example, Novavax has a vaccine candidate for older adults that has shown promising results in phase 3 trials. GlaxoSmithKline has an antibody product for pregnant women that is currently in phase 3 trials. And Sanofi Pasteur has a vaccine candidate for children aged 6 months to 5 years that is in phase 2 trials.
With these new tools and innovations, experts hope that RSV will soon become a preventable disease rather than a serious threat to public health.