Viral vaccine against respiratory syncytial virus in research.
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The U.S. Food and Drug Administration’s independent advisory panel on Thursday recommended full approval of Pfizer’s vaccine, which protects infants from respiratory syncytial virus. However, safety concerns have been raised about premature births that may be related to the syringe.
The committee unanimously stated that the data on the effectiveness of the vaccine were sufficient. Ten of the consultants said the safety data on Pfizer’s vaccine was adequate, while four said it was not.
“If the vaccine does indeed match the data we saw today, I can guarantee that many infants and their parents will breathe easier for years to come,” said Dr. Jay Portnoy, medical director at Children’s Mercy Hospital in Kansas City. after voting for the safety and effectiveness of the shot.
dr Paul Offit, a vaccines expert at Children’s Hospital of Philadelphia, said he doesn’t think there’s enough data to suggest the vaccine’s safety is “reassuring.”
“If you’re in any way risking preterm birth with this vaccine, I think there’s a big price to pay,” said Offit, who voted against the vaccine’s safety data.
Adam Berger, director of clinical research policy and health research at the National Institutes of Health, voted for the vaccine’s safety and effectiveness but said Pfizer’s post-marketing studies needed to examine the risk of preterm birth.
Post-marketing refers to studies conducted on a product after it has received FDA approval.
The FDA typically follows the advice of its advisory committees, but is not required to do so. The agency is scheduled to make a final decision on the shot in August, just ahead of the fall RSV season.
If approved, Pfizer’s vaccine would be the world’s first vaccine to protect infants from RSV — a goal scientists have been working towards for decades.
The FDA earlier this month approved GlaxoSmithKline’s first RSV vaccine for adults age 60 and older. The agency is expected to make a decision on Pfizer’s other RSV vaccine for the same age group within a few weeks.
RSV is a common respiratory infection that causes cold-like symptoms. Older adults and younger children are particularly susceptible to more severe RSV infections.
According to the Centers for Disease Control and Prevention, the virus kills 6,000 to 10,000 seniors and a few hundred children under the age of 5 each year. According to the CDC, about 1 in 100 children under 6 months of age with RSV infection may need hospitalization.
Pfizer’s vaccine for infants is given to expectant mothers in the late second or third trimester of their pregnancy. The single-dose vaccine elicits antibodies that are passed to the fetus, protecting it from RSV from birth until the first six months of life.
Weigh safety and efficacy data
A phase III study found that Pfizer’s vaccine was nearly 82% effective in preventing serious RSV disease in newborns in the first 90 days of life. The vaccination was also about 70% effective in the first six months of the baby’s life.
However, the concerns of the advisory panel arose from the safety data of this study.
Mothers who received the injection had a slightly higher rate of preterm births than mothers who received placebo: 5.7% versus 4.7%.
Both Pfizer and the FDA said the difference did not appear to be statistically significant.
Also, most infants, even if born prematurely, were born after 34 weeks gestation, just a few weeks before their due date.
But dr Hana El Sahly, Chair of the FDA Advisory Committee, said, “Even if it’s a late preterm birth, the fact that we are subjecting her to a preterm birth while we’re sitting here intellectually discussing the matter is not trivial.”
Preterm delivery is not a new problem when it comes to infant RSV vaccines.
Pfizer’s competitor GSK halted its own study of its RSV vaccine for newborns after it became aware of worrying data on preterm birth and neonatal deaths, or the death of a baby within the first 28 days of life.
Offit also said the GSK process “hangs out beyond Pfizer’s RSV vaccine for infants.”
“If GSK really abandons a program for a similar, almost identical vaccine, that’s going to stick [Pfizer’s] “I think it needs to be addressed.”
Portnoy added that preterm birth could potentially reduce the benefits of vaccination.
“The problem is that having the child earlier also reduces the effectiveness of the treatment because there are fewer antibodies transferred with earlier birth,” he said. “So this is a very complex thing because the harm actually outweighs the benefit. There is an interaction between the two.”
However, some members of the panel doubt that there is a clear causal link between the vaccine and preterm birth.
“Am I concerned about the imbalance in preterm birth? Yes. Am I convinced it’s real? No,” said Dr. Daniel Feikin, a scientific and respiratory advisor who voted for the safety of the vaccine.
Pfizer officials also dismissed the safety concerns, stressing that the benefits of vaccination outweigh the risks.
“In our view, there is certainly no clear evidence that there is a risk of preterm birth,” said Dr. William Gruber, senior vice president of clinical research and vaccine development at Pfizer. “So the question is, are you attributing the potential benefits of the vaccine to something that you don’t have statistical significance for as of this writing?”
Some of the participants’ children also had low birth weight and experienced developmental delays, the FDA staff assessment said.
Most of the more than 3,000 mothers who received the shot as part of the study experienced mild to moderate side effects, according to FDA staff data review.
The most common reactions were fatigue, myalgia, headache and injection site pain. Most reactions disappeared within three to four days after vaccination, the staff assessment said.
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