In June 2024, the U.S. Centers for Disease Control and Prevention (CDC) reported vaccine effectiveness of Pfizer’s ABRYSVO and GlaxoSmithKline’s (GSK) AREXVY to be between 73 and 82 percent effective against RSV related hospitalizations in persons 60 years of age and older based on data collected through several U.S. based RSV monitoring systems. The data, however, was reported at 3-4 months post-vaccine administration and not considered sufficient to determine vaccine effectiveness past one season. No vaccine effectiveness data is available for Moderna’s MRESVIA RSV vaccine.
There is no vaccine effectiveness data on the use of Pfizer’s ABRYSVO RSV vaccine in pregnant women due to low vaccine uptake, the timing of RSV vaccine availability, and the early onset of the RSV season in 2023 – 2024.
Pre-licensing clinical trials of all RSV vaccines evaluated vaccine efficacy, not vaccine effectiveness. Vaccine effectiveness is based on real-world data of how the vaccine works in the general population, which is not available until after the product is widely used in the target population.
Notably, vaccine efficacy can differ from vaccine effectiveness because a vaccine may not work as well in the real world. Understanding what efficacy and effectiveness mean is also important. Below is an example from Yale Medicine.
“An example: Imagine there were 100 people in the vaccine group, and 100 people in the placebo group. If 10 people in the placebo group became infected, but only 2 in the vaccine group got sick, that means the vaccine has reduced the chances of illness by 80%; thus, it is considered to have an efficacy of 80%.”
IMPORTANT NOTE: NVIC encourages you to become fully informed about Respiratory Syncytial Virus (RSV) and the Respiratory Syncytial Virus (RSV) vaccine by reading all sections in the Table of Contents, which contain many links and resources such as the manufacturer product information inserts, and to speak with one or more trusted health care professionals before making a vaccination decision for yourself or your child. This information is for educational purposes only and is not intended as medical advice.
