Pfizer plans to seek regulatory approval of its experimental respiratory syncytial virus vaccine following study results showing the shot was strongly protective against symptoms of the disease in a Phase 3 trial, the company announced Thursday.
Upon an interim look at study results, trial monitors found the shot to be about 67% effective at preventing moderate disease, or infections with at least two symptoms, in adults. The vaccine was roughly 86% protective against more severe disease, defined as an RSV-associated lower respiratory tract illness with at least three symptoms. The vaccine was also well-tolerated with no indicated safety concerns, according to the statement.
Pfizer didn’t provide more detailed results. The data will be presented at a future medical meeting and submitted for peer-review in a scientific journal. Study enrollment is still underway, meaning the numbers could change after investigators perform a final analysis.
In the meantime, the company is preparing to file for regulatory approvals this fall in the U.S. and elsewhere, keeping pace with a similar shot from British drugmaker GSK that’s also succeeded in a Phase 3 study in adults.
The two vaccines have the potential to be the first protective options against RSV.
A common respiratory infection. RSV usually only causes mild, cold-like symptoms. Infections with the virus can be deadly in children younger than 5 and adults older than 65, however. RSV typically kills 14,000 elderly adults annually, according to the Centers for Disease Control and Prevention. Currently, treatments only manage symptoms.
Scientists and drugmakers have tried, unsuccessfully, since the 1960s to develop a protective shot. But efforts have accelerated in recent years, since scientists at The National Institutes of Health made a discovery that helped drugmakers understand how to stimulate an immune response against RSV.
Along with Pfizer and GSK, Johnson & Johnson and Moderna are also working on RSV vaccines. GSK recently claimed success in a Phase 3 trial, but didn’t provide specific details. Earlier, in February, GSK halted a trial in pregnant women due to possible safety issues. GSK will seek regulatory approval later this year.
Moderna and J&J also have vaccine candidates in late-stage trials.
Pfizer tested its shot in adults over the age of 60 and pregnant women.