Pfizer Initiates Phase 3 Clinical Trial of RSV Vaccine in Adults

Pfizer recently initiated a Phase 3 clinical trial evaluating the efficacy, immunogenicity, and safety of a single dose of its respiratory syncytial virus (RSV) vaccine candidate in adults.

The placebo-controlled RENOIR study will enroll nearly 30,000 participants 60 years of age and older. The study’s primary objective is the prevention of moderate to severe lower respiratory tract illness during the first RSV season. 

“There is an important unmet medical need for an effective vaccine that can help protect older adults against this highly-contagious disease,” Kathrin U. Jansen, PhD, senior vice president and head of vaccine research & development at Pfizer, said in the announcement. 

“The start of this Phase 3 study is an important step forward towards our goal of comprehensive immunization against RSV disease, which includes developing a potential first vaccine to help prevent RSV disease in adults as well as the ongoing efforts to help protect infants through maternal immunization,” Jansen continued. 

RSV leads to nearly 58,000 hospitalizations annually among children younger than five years old, 177,000 hospitalizations among adults 65 years of age and older, and 14,000 deaths among adults 65 years and older, according to the CDC. 

Although there are currently no vaccines to prevent RSV, big pharma companies, including Moderna and AstraZeneca, have developed promising RSV vaccine candidates over the last year. 

In April 2021, Moderna stated that its RSV vaccine candidate, mRNA-1345, generated a geometric mean rise in neutralizing antibodies relative to baseline at least 11-fold and increased RSV neutralizing antibodies in seropositive younger adults.

And in August, FDA granted Fast Track designation to mRNA-1345 for use in adults 60 years of age and older. 

Moderna plans to evaluate the potential combinations of mRNA-1345 with its vaccines against other respiratory pathogens in children and separately in older adults.

In July, AstraZeneca announced that its long-acting antibody, nirsevimab, demonstrated a positive safety profile and tolerability profile in infants at high risk of RSV in a Phase 2/3 clinical trial. 

The MEDLEY 2/3 trial evaluated nirsevimab compared to Synagis when given to infants with chronic lung disease, congenital heart disease, prematurity, or those entering their first RSV season.

AstraZeneca will present full results from MEDLEY in the near future. The ongoing trial will also collect additional safety data.