There are data to support the contention that term infants born to mothers with higher naturally occurring anti-RSV neutralizing antibodies benefit from those antibodies. In a large prospective cohort study performed in Kenya, cord blood anti-RSV antibody concentrations correlated directly with the length of time before the infant’s first RSV infection. It’s therefore logical to conclude that administering an effective RSV vaccine during pregnancy could augment that natural antibody response, be transferred to the infant at birth, and offer protection against RSV when exposed.
Several candidate vaccines for study already exist and have undergone phase I testing in nonpregnant adults. Once safety is demonstrated, the next step is to identify the vaccine formulation resulting in the most robust anti-RSV neutralizing antibody concentrations. Such a candidate vaccine will be chosen for future phase III trials during pregnancy. Safety, and maternal/cord blood RSV antibody titers will be of interest during that clinical trial, but the rates and timing of RSV infection and RSV-associated hospitalizations among the infants born to those mothers will be the most instructive.
Ideally, a candidate RSV vaccine shown to be as safe and as effective during pregnancy as inactivated influenza vaccines and/or Tdap vaccines would be implemented immediately and universally. Unfortunately, substantial vaccine hesitancy for the use of influenza and Tdap vaccines continues among pregnant patients and their providers. Acceptance of an RSV vaccine for use during pregnancy will not come easily, or immediately. As with all of our successful vaccine programs, launching such an effort will require education, patience, and careful post-licensure documentation of the impact that the intervention has in the real world.
Dr. Domachowske is professor of pediatrics and professor of microbiology and immunology at the State University of New York Upstate Medical University, Syracuse, N.Y. Dr. Domachowske is performing clinical trials and has grants in the area of RSV prevention with Astra Zeneca, Regeneron, and Glaxo Smith Kline.