WASHINGTON — A unique RSV vaccine for pregnant women protects their newborns from the scary respiratory virus — and federal health advisers debated Thursday whether Pfizer’s vaccine is ready for rollout.
RSV fills hospitals with panting babies every fall and winter, and the virus hit earlier than usual and particularly hard in the United States last year.
Vaccination of expectant mothers “would have a big impact,” said Dr. Alejandra Gurtman, director of vaccine research at Pfizer.
The idea: Give women a single injection late in pregnancy, between weeks 24 and 36, so they develop RSV-fighting antibodies that cross the placenta — just as they give their babies protection from other bacteria.
At Pfizer International Studies In nearly 7,400 pregnant women, maternal vaccination was found to be 82% effective in preventing severe RSV infection in the first trimester of the babies who were most at risk. At 6 months of age, it still protected 69% from serious disease.
Pfizer said there were no signs of safety issues, and in an analysis released ahead of Thursday’s meeting, FDA reviewers agreed that “safety data appears to be generally positive.” However, the FDA has asked its scientific advisers to consider whether a slight difference in preterm birth between the two groups is a cause for concern.
Should the Food and Drug Administration ultimately approve maternal vaccination, it would mark a second milestone in the decade-long effort to prevent respiratory syncytial virus. Earlier this month, the FDA granted approval the world’s first RSV vaccine, competes with GSK’s vaccine for older adults, who are also at high risk. There’s no vaccine for children yet, but Pfizer is about to start testing one.
Here are some things you should know:
RSV IS A COMMON THREAT
For most healthy people, RSV is a common cold-like nuisance. But it can be life-threatening for tiny ones — an infection deep in the lungs causing pneumonia, or preventing babies from breathing by inflaming their tiny airways. According to the Centers for Disease Control and Prevention, between 58,000 and 80,000 children under the age of five are hospitalized and between 100 and 300 die each year in the United States alone.
“All young infants are at risk of serious RSV disease,” but postponing infection by just a few months reduces that risk, said Dr. Katherine Fleming-Dutra of the CDC.
POSSIBLE EFFECTS OF THE VACCINE
Pfizer’s vaccine isn’t designed to prevent RSV infection, but to prevent the worst of it. In late-stage testing, six infants born to vaccinated mothers had severe RSV disease within the first three months of life, compared with 33 infants born to mothers who received a sham vaccine. In addition, the vaccine halved the likelihood of needing medical attention for RSV infection at 6 months of age.
The company predicts that the US could prevent up to 20,000 infant hospitalizations and 320,000 doctor visits annually if enough pregnant women were vaccinated.
SECURITY DATA
Vaccination reactions typically included mild pain at the injection site and fatigue. Regarding the question of preterm births, vaccinated mothers had slightly more preterm births – 5.7% versus 4.7%. The vast majority were born just a few weeks premature. That’s better than the country’s preterm birth rate — overall, one in 10 babies was born prematurely in the US last year — and the study imbalance wasn’t statistically significant, meaning it could be due to chance.
A total of 17 infants died during the study, five from vaccinated mothers and 12 from mothers given a sham vaccine. Researchers assumed none of the deaths were related to the vaccine, but the FDA said it was “unable to rule out the possibility” that the death of an infant, which was a result of extreme preterm birth, was related could stand.
Vaccines are always subject to scrutiny for safety, but regulators are particularly aware of a major setback in the 1960s, when an experimental RSV vaccine made infections worse in children. Eventually, scientists figured out the problem, and the RSV vaccines in the pipeline today are made using safer, modern methods — but were still tested in older adults first.
WHAT HAPPENS NEXT?
FDA advisers have already recommended that Pfizer’s vaccine be approved for older adults, and the agency is expected to make a decision by the end of the month. Whether to use the same vaccine in pregnant women will be a separate decision from the FDA, expected in August.
Meanwhile, competitor GSK is gearing up for fall vaccinations with its RSV vaccine for seniors. First, over the next month, CDC advisors will discuss whether all older adults need vaccination or just those at high risk.
Vaccines aren’t the only advancement in the pipeline. High-risk infants often receive monthly doses of a protective drug during RSV season, but European regulators recently approved Sanofi and AstraZeneca’s first single-dose option. FDA advisors will also discuss this drug next month.
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