Clinical trial results have shown that an RSV vaccine developed by Pfizer offers safe and effective protection for both seniors and newborns. The vaccine is 86% effective in protecting older adults from severe RSV infections that cause three or more symptoms, while it is 82% effective in protecting newborns from respiratory infections that require hospitalization if their expectant mothers receive the vaccine in their second or third trimester. Dr. Bill Gruber, the senior vice president and head of clinical vaccine research and development for Pfizer, has described the results as a “fantastic advance for world health.”
Respiratory syncytial virus (RSV) is a mild respiratory virus that can cause bronchiolitis and pneumonia in children under age 1. RSV infections are responsible for between 58,000 and 80,000 hospitalizations of children under age 5 each year in the US. RSV also poses a risk to older adults, with an estimated 60,000 to 160,000 US seniors hospitalized and 6,000 to 10,000 dying from RSV infection annually.
The Pfizer vaccine targets RSV’s F protein, which the virus uses to invade human cells. Previous attempts to create an RSV vaccine in the 1960s failed because the vaccine caused a phenomenon called antibody-dependent enhancement, where the antibodies produced by a vaccine actually make a virus more virulent and harmful. However, in the early 2010s, US National Institutes of Health researchers discovered that the F protein changes shape after it binds with a human cell. This breakthrough prompted a race among pharmaceutical companies to craft a safe and effective RSV vaccine.
For the clinical trial in older adults, researchers assigned more than 34,000 people aged 60 or older to receive either the Pfizer RSV vaccine or a placebo. Results showed that the vaccine was 86% effective in preventing severe cases of RSV involving three or more symptoms and 67% effective in stopping an RSV infection involving at least two symptoms. In the clinical trial in pregnant women, over 7,300 females randomly received either the Pfizer vaccine or a placebo, and their newborns were then tracked to see if maternal antibodies produced by the vaccine conferred any protection to the babies. The vaccine provided nearly 82% protection against severe lower respiratory tract infections that required hospitalization within 90 days of birth.
Pfizer expects an FDA decision on the RSV vaccine for seniors by May and for pregnant women by August. Safety will continue to be evaluated, and Pfizer will continue to track vaccinated people going forward to see how long the vaccine’s protection lasts.
