Drugmakers have labored for decades to successfully develop a vaccine to protect infants and older people against infections of a common pathogen called respiratory syncytial virus. Multiple large pharmaceutical companies could finally be on the precipice of that goal, each with a chance to bring a vaccine to market within two years.
One of them could be Pfizer, which surprised investors and analysts this week by announcing plans to start a Phase 3 trial of an RSV vaccine in adults within two months and complete it in early 2022. That pace beats previous expectations and could put Pfizer on pace with GlaxoSmithKline in the race to deliver a preventive shot.
A lucrative prize awaits the winner. In the U.S., RSV results in 58,000 hospitalizations a year in children younger than 5 and 177,000 in the elderly. Analysts from Cowen project that an effective vaccine could generate more than $7 billion in sales by 2028, revenue that could recur if patients need periodic boosters.
"This is the second leading cause of respiratory illness following flu," Angela Hwang, Pfizer's biopharmaceuticals group president, said in a conference call with analysts. "It's really in the sweet spot of what we do with adult vaccinations and and also seasonal vaccinations."
RSV has multiple treatments available, from the antiviral drug ribavirin to bronchodilators for people with lung conditions. An antibody called Synagis from Swedish Orphan Biovitrum can also help prevent RSV in high-risk infants.
But developing a successful vaccine has been a more elusive goal. The first potential vaccine was tested in the 1960s but failed becuase of safety problems. It stimulated antibodies that weren't protective as well as a type of immune response that can make the disease worse.
The current crop of vaccines, including Pfizer's, have largely focused on a viral protein called F that is the target of antibodies the body churns out naturally to neutralize the virus.
GSK had been at the forefront of the effort in adults. The British drugmaker has an experimental shot for infants in early-stage testing, and vaccines for pregnant women and older adults in Phase 3 trials. Johnson & Johnson, too, has a shot in advanced testing, though it's a bit further behind.
Now, however, Pfizer appears to have caught up. If Pfizer and GSK succeed in clinical testing, approval filings for each of their vaccines for adults could be on regulators' desks next year.
In its second-quarter earnings presentation, Pfizer announced the results of a Phase 2 "challenge" study in healthy adults 18 to 50 years of age. None of the 31 vaccinated volunteers showed signs of mild or moderate RSV disease.
The company hasn't disclosed the design of its Phase 3 trial. SVB Leerink analyst Geoffrey Porges, citing other, similar trials, speculated the study might include 25,000 volunteers over 65 years of age, with the vaccine's goal being to prevent symptomatic infections.
GSK hasn't announced a Phase 3 trial of that scale, with its main study having enrolled 1,700 patients and evaluated immune responses rather than infection rates. But the program is important to GSK. Its RSV vaccines were among several experimental candidates the company has highlighted to investors as its route to boost lagging sales.
Meanwhile, more competition may be coming. Moderna, for instance, is using the same messenger RNA technology used to develop a coronavirus vaccine to make a shot to prevent RSV in adults. Moderna expects to have data from an early trial in multiple age groups next year.
Vaccines for younger groups have attracted more competition, with Sanofi, Glaxo and Moderna each pursuing projects developed by the National Institutes of Health.