CASE Pregnant woman asks about the RSV vaccine
A 28-year-old primigravid woman at 30 weeks’ gestation inquires about the new vaccine to protect her newborn baby against respiratory syncytial virus infection (RSV). Her neighbor’s daughter recently was hospitalized for the treatment of RSV, and she is understandably concerned about her own newborn. The patient is healthy, and she has never had any serious respiratory infection. She is taking no medications other than prenatal vitamins.
What advice should you give her?
If you decide to administer this vaccine, what is the appropriate timing of administration?
Are there any maternal or fetal safety concerns related to use of this vaccine in pregnancy?
Respiratory syncytial virus (RSV) is a member of the Paramyxoviridae family. It is an enveloped, single-stranded RNA virus that is 150-300 nm in size. The virus codes for 10 virus-specific proteins. The 2 most important are the G protein, which enables the virus to attach to host cells, and the F protein, which facilitates the entry of the virus into the host cell by fusing the host and viral membranes. Two distinct subtypes exist: A and B. There is genetic variation within each subtype and between subtypes. These subtle genetic variations create the potential for reinfections, and hence, research has focused on development of a vaccine that covers both subtypes.1
RSV is the most common cause of acute lower respiratory tract infection in infants younger than 6 months of age. In these children, RSV is one of the most prominent causes of death, with mortality particularly marked in low- and middle-resource countries as well as in children who were born premature and/or who are immunocompromised. RSV has its greatest impact during winter epidemics in temperate climates and during the rainy seasons in tropical climates. The virus rarely is encountered in the summer.1 Among young children, RSV primarily is transmitted via close contact with contaminated fingers or fomites and by self-inoculation of the conjunctiva or anterior nares. The incubation period of the infection is 4 to 6 days, and viral shedding may persist for 2 weeks or longer. Most patients gradually recover within 1 to 2 weeks.1 Adults who contract RSV usually have symptoms suggestive of a common cold; however, in older adults or those who have comorbidities, serious and potentially life-threatening lower respiratory tract infections may develop.
Recently, there have been 2 main approaches to the prevention and treatment of RSV in infants. One has been the development of monoclonal antibodies such as motavizumab, palivizumab, and nirsevimab. The other has been the development of a vaccine that could be administered to pregnant women and which could provide protection for the neonate in the early months of life.2,3
In late August 2023, the US Food and Drug Administration (FDA) announced the approval of a new bivalent RSV prefusion F vaccine (ABRYSVO, Pfizer) intended for administration to pregnant women.4 Of note, previous efforts to develop whole-virus vaccines either have been ineffective or have potentiated the disease in infants who became infected; development of an effective vaccine had eluded scientists and clinicians for nearly 50 years.2 Thus, the new vaccine that targets the F protein of the virus represents a major and welcomed breakthrough.
This article reviews the 3 most recent investigations that preceded the ultimate approval of this vaccine and discusses specific logistical issues related to vaccine administration.
Continue to: First step toward vaccine approval...