FDA advisors support the RSV vaccine for pregnant women that protects their newborn babies

WASHINGTON (AP) — A first-of-its-kind RSV vaccine for pregnant women to protect their newborn babies from the dreaded respiratory virus — federal health advisors on Thursday backed Pfizer’s shot despite some lingering questions.

RSV fills hospitals with wheeze in babies Every fall and winter, the virus hits earlier than usual, especially in the United States last year.

If the vaccine stops, “many children and their parents will breathe easier in the years to come,” said Dr. Jay Portnoy, a member of the Food and Drug Administration’s advisory committee at Children’s Mercy Hospital in Kansas City, Missouri.

The idea: Give women a single shot late in their pregnancy, between 24 weeks and 36 weeks, so they develop antibodies against respiratory syncytial virus (RSV) that pass through the placenta — just as they pass protection against other bugs on to their babies.

In the Pfizer International Study Among nearly 7,400 pregnant women, maternal vaccination proved 82% effective in preventing acute respiratory syncytial virus during the first three months of life in the most vulnerable infants. At 6 months old, 69% of it was still shown to protect against severe disease.

Pfizer said there were no signs of safety issues, but the Food and Drug Administration asked its scientific advisors to consider whether the slight difference in preterm labor between vaccinated mothers and those given a dummy injection was of concern. Debate over whether this was really a sign of trouble or by chance dominated the day-long committee meeting.

Pfizer has pledged to closely monitor real-world use of the vaccine for more evidence. In the end, the advisors unanimously decided the shot was effective — and voted 10-4 that there was enough safety data. The Food and Drug Administration will consider Thursday’s recommendations in making the final decision on approval.

Among the panelists who voted “no” on the safety question was Dr. Paul Offit of the Children’s Hospital of Philadelphia.

If the FDA eventually approves the shot for the mother, it will be another milestone in the decades-old quest for prevention of respiratory syncytial virus. Earlier this month, the FDA approved the world’s first RSV vaccine, a competing GSK injection for the elderly, who are also at high risk. There is 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 cold-like nuisance. But it can threaten the lives of the very young – who get infected deep in the lungs by causing pneumonia or by obstructing children’s breathing by inflaming their small airways. In the United States alone, between 58,000 and 80,000 children under the age of 5 are hospitalized each year, and between 100 and 300 children die, according to the Centers for Disease Control and Prevention.

“All young children are at risk of becoming severely ill with RSV,” said Dr. Catherine Fleming-Dutra of the CDC, but postponing infection even for a few months reduces that risk.

Possible effect of the vaccine

The Pfizer vaccine is not intended to prevent RSV infection but to avoid the worst outcomes. In a late-stage test, six infants born to vaccine-vaccinated mothers became severely ill with RSV in their first three months of life compared to 33 infants whose mothers received a dummy injection. In addition, the vaccine cut in half the chances of needing any medical care for RSV infection by 6 months of age.

The company predicts that the United States could prevent up to 20,000 hospitalized babies a year, and 320,000 doctor visits, if enough pregnant women are vaccinated.

Safety data

Vaccine reactions usually included mild pain at the injection site and fatigue. For the prematurity question, vaccinated mothers had slightly more premature babies – 5.7% vs. 4.7%. The vast majority are born a few weeks early. That’s better than the country’s preterm birth rate — overall in the US, 1 in 10 babies was born premature last year — and the imbalance in the study wasn’t statistically significant, which means it could be due to chance.

Rival GSK has halted its own trials of the maternal RSV vaccine over prematurity concerns, raising questions about Pfizer’s dose. Pfizer said the premature difference in its study was driven by participants in South Africa — for reasons unknown — and no difference was seen in the United States or other high-income countries.

“Are you holding the potential benefits of a vaccine hostage,” Pfizer vice president Dr. William Gruber asked panelists without clear evidence of a problem.

“There is certainty that the vaccine works and will keep children out of hospital in the United States once this winter,” he said.

A total of 17 infants died during the study, five born to vaccinated mothers and 12 to those given a dummy injection. The researchers did not believe any 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, caused by extreme prematurity, might be related.

Vaccines are always subject to close safety scrutiny, but regulators are particularly aware of a major setback in the 1960s when an experimental RSV shot exacerbated infections in children. Eventually scientists discovered the problem and the RSV vaccines in the pipeline today are made with safer, more modern methods – yet they are still being tested first on the elderly.

Another open question

FDA advisors also cautioned that it is not clear what other vaccines for pregnant women may be given during the same doctor’s visit. They pointed to data that a pertussis vaccine does not appear to be as potent if pregnant women receive it at the same time as the RSV vaccine.

what happened after that?

FDA advisors have already recommended approval of Pfizer’s vaccine for seniors, and the agency is expected to make a decision by the end of the month. The FDA’s decision will be separate on whether to use the same shot in pregnant women in August.

Meanwhile, rival GSK is preparing for a fall immunization with an RSV vaccine for seniors. First, CDC advisors will discuss next month whether all older adults or only those at high risk need to be vaccinated.

Vaccines aren’t the only advances in the pipeline. High-risk infants can get monthly doses of a preventative medication during RSV season, although CDC data shows very few receive them. European regulators recently approved the first single-dose option, from Sanofi and AstraZeneca, opening up this type of protection to more children. FDA advisors will discuss this drug next month as well.


The Associated Press Health and Science section receives support from the Howard Hughes Medical Institute’s Division of Science Education. AP is solely responsible for all content.

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