Pfizer Announces Encouraging Data on RSV Vaccine for Pregnant Persons


Respiratory syncytial virus (RSV) can be deadly for newborns and young infants. The newest information from Pfizer about its RSCpreF investigational vaccine is promising for new mothers and infants through the first 90 days of life.

A picture of a Pfizer sign on a wall.

A picture of a Pfizer sign (Adobe Stock)

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Because of the risks that newborns face from respiratory syncytial virus (RSV), the news from Pfizer today is encouraging. While monoclonal antibodies have been around for decades, a more cost-effective preventative strategy is needed.Pfizer announced this morning topline data for its RSVpreF investigational vaccine for expecting mothers demonstrating a high efficacy in its phase 3 trial. Specifically, when looking at severe medically attended lower respiratory tract illness (severe MA-LRTI) the efficacy for the vaccine was 81.8% (CI: 40.6%, 96.3%) through the first 90 days of life. In addition, substantial efficacy of 69.4% (CI: 44.3%, 84.1%) was demonstrated for infants over the six-month follow-up period.

“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,” Annaliesa Anderson, PhD, senior vice president and chief scientific officer, Vaccine Research & Development, Pfizer, said in a statement.

The results are from its phase 3 MATISSE trial.

RSV continues to be a challenge for the youngest in the pediatric population. Hospitals and clinicians in some areas of the United States are reporting overcapacity at their facilities.

Pfizer said in the statement that the pre-planned, interim efficacy analysis conducted by an external and independent Data Monitoring Committee (DMC) met the success criterion for one of two primary endpoints. The observed efficacy for severe medically attended lower respiratory tract illness (severe MA-LRTI) was 81.8% (CI: 40.6%, 96.3%) through the first 90 days of life. Substantial efficacy of 69.4% (CI: 44.3%, 84.1%) was demonstrated for infants over the six-month follow-up period.

Although the statistical success criterion was not met for the second primary endpoint, clinically meaningful efficacy was observed for MA-LRTI of 57.1% (CI: 14.7%, 79.8%) in infants from birth through the first 90 days of life. Efficacy for MA-LRTI of 51.3% (CI: 29.4%, 66.8%) was observed over the six-month follow up period.

The vaccine was considered to be well-tolerated.

At the recommendation of the DMC, and after consultation with the FDA, Pfizer stopped enrollment in the study. With these positive results, the company plans to submit a Biologics License Application (BLA) to the FDA by the end of this year for the RSVpreF vaccine.

“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 said in the same statement.

Another vaccine trial by GlaxoSmithKline is demonstrating promise also.

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