The Pfizer pharmaceuticals firm announced Tuesday that its experimental vaccine significantly reduces the risk of newborn infants contracting severe cases of RSV (respiratory syncytial virus), an illness which kills hundreds of babies and toddlers each year.
RSV usually causes a simple cold in healthy adults. However, it can be deadly in babies under a year and in the elderly.
Higher-than-normal rates of hospital admissions of babies with RSV were reported this year in the United States.
The Phase 3 clinical trial, carried out in 18 countries around the world, beginning in June 2020, spanned multiple RSV seasons in both the northern and southern hemispheres.
The vaccine received Breakthrough Therapy Designation by the US Food and Drug Administration (FDA) on March 2, 2022 after the company submitted the results of its Phase 2b proof-of-concept study.
Tuesday’s announcement said the vaccine was 81.8 percent effective when administered to pregnant women.
Infants whose mothers received the vaccine while pregnant had an 81.8 percent lower risk of developing the illness in the first three months after birth, compared to those whose mothers had received a placebo.
The vaccine was 69.4 percent effective for infants over the six-month follow up period.
Pfizer said it intend to submit the findings for publication in a peer-reviewed scientific journal.
The study enrolled approximately 7,400 pregnant women between the ages of 18 and 49 years old who received a single dose of the vaccine or a placebo during the late second to third trimester. The participants were followed up for six months after delivery.
Safety reviews carried out during the study by an independent, external Data Monitoring Committee indicated the vaccine was well tolerated “with no safety concerns for both the vaccinated individuals and their newborns,” the company said.
“We are thrilled by these data as this is the first-ever investigational vaccine shown to help protect newborns against severe RSV-related respiratory illness immediately at birth,” said Annaliesa Anderson, Ph.D., Senior Vice President and Chief Scientific Officer, Vaccine Research & Development, Pfizer.
“We look forward to working with the FDA and other regulatory agencies to bring this vaccine candidate to expectant mothers to help protect their infants against severe RSV during their most vulnerable first six months of life, which has the highest burden of RSV illness in infants.”
Anderson thanked the pregnant women who volunteered for the trial “along with their infants” and the investigators around the world who participated in the study.
Pfizer said it plans to submit a Biologics License Application (BLA) to the FDA by the end of 2022 for the vaccine candidate followed by other regulatory authorities in the coming months.
“A maternal vaccine with high efficacy that can help protect infants from birth could substantially reduce the burden of severe RSV among newborns through six months of age, and, if approved by regulatory authorities, will likely have a significant impact on disease in the US and globally,” said Eric A.F. Simões, MD, Clinical Professor, Pediatrics-Infectious Diseases, University of Colorado School of Medicine and Children’s Hospital Colorado, Aurora.
RSV is a contagious virus and a common cause of respiratory illness. The virus can affect the lungs and breathing passages of an infected individual and can be potentially life-threatening for young infants, persons with certain chronic medical conditions, and older adults.
In the United States alone, approximately 2.1 million outpatient visits and 58,000 hospitalizations due to RSV occur each year among children younger than five years old.
Worldwide, RSV results in death of approximately 102,000 children annually, with about half of those in infants less than six months old and the vast majority in developing countries.
RSV bronchiolitis is the leading cause of infant hospitalization due to viral respiratory illness, characterized by respiratory distress that can result in death. There is no specific treatment for RSV, only supportive care measures like oxygen and fluids. Currently there is no vaccine to prevent RSV. The only available preventive agent is recommended for use in limited settings in the highest-risk infants as a monthly injection with five doses administered during the RSV season, leaving most infants without protection.