An experimental vaccine for respiratory syncytial virus, or RSV, boosted pre-existing immune responses in young women and had a safety profile similar to that of the Tdap vaccine, according to the results of a pair of phase 2 trials.
The virus, which causes more than 30 million acute respiratory tract infections in children around the world each year, has stymied researchers attempting to create an RSV vaccine for decades. In September 2016, Novavax announced that a phase 3 trial among older adults had failed.
“Placental antibody transfer can offer protection against RSV, as high titers of maternally derived RSV-neutralizing antibodies are inversely associated with RSV [lower respiratory illness] during the first 6 months of life,” Jirí Beran, MD, PhD, of the Vaccination and Travel Medicine Centre, Hradec Králové, Czech Republic, and colleagues wrote in The Journal of Infectious Diseases. “Maternal immunization boosts maternal RSV antibody titers, and thus has the potential to protect young infants against RSV during the first months of life.”
Beran and colleagues performed two observer-blind, phase 2, randomized controlled trials of the RSV-PreF vaccine. The RSV F-020 trial (n = 500) was conducted at various sites in the U.S., the Czech Republic, Australia and Germany, whereas the RSV F-024 trial (n = 100) was carried out at one center in Belgium. RSF F-020 evaluated three different RSV-PreF formulations. Based on the results of the RSV F-020 study, the researchers conducted the RSV F-024 trial to evaluate the safety of the 60 µg nonadjuvanted RSV Pre-F vaccine compared with Tdap. All patients were women aged 18 to 45 years.
In both studies, the RSV-PreF vaccine showed a similar reactogenicity profile to Tdap, the researchers reported. At 30 days, women in the RSV F-020 trial who received the vaccine had RSV-A neutralizing antibodies ranging from 3.1 to 3.9 times greater than baseline. Concentrations of antibodies that compete with Synagis (palivizumab, AstraZeneca) rose by more than 14-fold by day 30, and although RSV antibody titers fell after 30 days, they remained at more than double pre-vaccination levels at 90 days, Beran and colleagues wrote.
The researchers reported that there were no serious vaccine-related adverse events.
“In conclusion, all three formulations of an experimental RSV-PreF vaccine boosted pre-existing immune responses in [18 to 45-year-old] women, with comparable immunogenicity,” Beran and colleagues wrote. “The RSV-PreF safety profile was similar to Tdap.” – by Andy Polhamus
Disclosures: Beran reports grants from GlaxoSmithKline based on the study budget as agreed by the European Commission for performing the trial in the Czech Republic. Please see the study for all other authors’ relevant financial disclosures.