Lisa Jarvis

Pfizer’s RSV Vaccine Succeeds Where Others Failed

As parents worry over the cases of RSV filling up pediatric hospitals in the US, finally some good news: Vaccines that protect newborns from the virus could be ready in time for next year’s season. Pfizer Inc. today unveiled promising data on a maternal RSV shot that shows it lowered babies’ risk of severe infections in those vulnerable first months of life.

The early data has some caveats, but should be celebrated as a significant advance in a field that has suffered decades of setbacks. It is also an important next step in Pfizer’s goal of becoming a leader in addressing RSV — a global market that according to Bloomberg Intelligence could be worth $10 billion in 2030.

In Pfizer’s trial, pregnant women were given an RSV vaccine with the idea that any immunity generated would be passed onto their infants, a strategy already used for other respiratory viruses, like pertussis and the flu. The hope was that protection would last through the babies’ first six months of life, the period when they are most vulnerable to serious RSV infections.

The approach seems to be largely working. The maternal RSV vaccine lowered by nearly 82% the rate of severe cases of the respiratory infection in the first three months of an infant’s life, and by roughly 69% over the first six months. But the vaccine fell short of its goal of protecting against all infections. Pfizer now plans to ask the Food and Drug Administration to approve the shot, which could in theory be ready in time for next year’s RSV season.

Full details of the study have yet to be shared, but these early results are promising, says Peter Hotez, co-director of the Center for Vaccine Development at Texas Children’s Hospital. During his career, Hotez has taken care of a lot of infants with RSV. “It’s a devastating illness,” especially for babies who spent time in the neonatal unit or have underlying respiratory issues, he says. “We need an RSV vaccine.”

Getting to one has proven much more challenging than researchers had hoped. The field suffered a devastating setback in the 1960s, when infants who received an experimental RSV vaccine got much sicker from the virus than those who did not get the shot. It took decades to unravel the cause of that failure and design a vaccine that could overcome the flaws of the earlier shot.

And even with much more insight into how to tackle the virus, pharma companies have struggled to get a shot to market: Earlier this year, a worrisome safety signal caused GSK PLC, formerly GlaxoSmithKline, to halt enrollment in a study of its maternal RSV vaccine.

Given the daunting challenge, Pfizer’s success should be celebrated for making headway against a difficult virus. But it also leaves some room for other products in development. Because the vaccine didn’t hit the high bar of preventing infections, and some children continue to be vulnerable during and beyond that six-month window, a gap in protection still needs to be filled.

One possible solution is an antibody therapy being developed by Sanofi SA and AstraZeneca PLC. The one-time shot is meant to protect at-risk infants throughout an entire RSV season. By contrast, an existing antibody drug called Synagis, sold by the Swiss pharma firm Swedish Orphan Biovitrum AB (known as SOBI), has to be given monthly.

A longer-term possibility could be to develop a booster that would help extend protection beyond infancy, Hotez says. That’s a similar strategy as the one taken with the pertussis vaccine — the baby first gets protection through a vaccine given to the mother during pregnancy, then through shots during infancy. Pfizer, however, is not currently pursuing such a strategy.

Even with questions over whether the parents and physicians will opt for a vaccine over an antibody, today’s data reinforces Pfizer’s aspirational leadership position in tackling the virus. The company is in a heated race with GSK to be the first to commercialize a vaccine for older adults — an equally important, and much more lucrative, market. Bloomberg Intelligence analyst John Murphy puts the adult RSV vaccine market at $7-$8 billion, or 70-80% of the overall RSV product market. Pfizer is also in the early stages of developing an antiviral for RSV that came through its April acquisition of ReViral.

No matter who wins, the competition is good news for worried parents and overburdened hospitals.