RSV Vaccine development: Pfizer shares promising results

The new findings raise the prospect that one or more vaccines could be available before the RSV season next fall.

NEW YORK – New research shows that vaccinating pregnant women has helped protect their babies from the common but dreaded respiratory virus called RSV that inundates hospitals with young babies. wheezing every autumn.

Preliminary results offer hope that after decades of failures and disappointments, a vaccine against RSV may finally be on the verge of success.

Pfizer announced Tuesday that a large international study found that vaccinating mothers-to-be is nearly 82% effective at preventing severe cases of RSV during the first 90 days of vulnerable life. most of infants. At the age of 6 months, the vaccine still proved 69 percent effective against serious diseases – and there were no indications of a safety issue in the mother or infant.

“Mothers are always passing on antibodies to their babies,” said virologist Kena Swanson, vice president of viral vaccines at Pfizer. “Vaccines just put them in a much better position” to form and transmit antibodies against RSV.

Vaccination isn’t just about protecting babies. RSV is also dangerous for older people, and both Pfizer and rival GSK recently announced that their competitive shots also prove protective for the elderly.

None of this year’s findings will help this year as an early rise in RSV has packed children’s hospitals. But they do raise the prospect that one or more vaccines could be available before the RSV season next fall.

Dr William Schaffner, an infectious disease specialist at Vanderbilt University, said: ‘My fingers are crossed. “We’re infiltrating.”

Tuesday’s data was reported in a press release and has not been examined by independent experts.

Here is a long search for the RSV vaccine.


For most healthy people, RSV, or respiratory syncytial virus, is a cold-like nuisance. But for the very young, the elderly, and those with certain health problems, it can be serious, even life-threatening. The virus can infect deep within the lungs, causing pneumonia, and in infants it can interfere with breathing by inflaming the small airways.

In the US, about 58,000 children under the age of 5 are hospitalized with RSV each year and several hundred die. Among adults 65 and older, about 177,000 are hospitalized with RSV and 14,000 die annually.

Worldwide, RSV kills about 100,000 children each year, mainly in poor countries.


A tragedy in the 1960s reset the entire field. Using an approach that led to the first polio vaccine, scientists built an experimental RSV vaccine by culturing the virus in the lab and killing it. But the children’s trial not only found the vaccine had no protection, those who got RSV after getting the vaccine got worse. Two people died.

“Over a 20-year period, despite the advancement of science, nobody wanted to get close to developing an RSV vaccine,” says Schaffner.

He notes that even today’s modern RSV vaccine candidates are being tested in older adults, not children.


Modern vaccines tend to target the outer surface of the virus, which the immune system sees when the germ enters. For RSV, that target is the so-called F protein that helps the virus attach to human cells. Once again there’s a barrier: The protein is a shape-shifter, rearranging its shape before and after it “fuses” with the cells.

Structural biologist Jason McLellan of the University of Texas at Austin explains that the immune system only forms effective antibodies against RSV when it detects what is called a pre-fusion version of that protein.

In 2013, McLellan and virologist Barney Graham were working at the National Institutes of Health when they figured out the exact shape and figured out how to freeze it in that form. That discovery opened the way for today’s development of many experimental RSV vaccines.

(That same discovery was key to the hugely successful COVID-19 vaccine, as the coronavirus is also encased in a shape-shifting surface protein.)


Several companies are making RSV vaccines, but Pfizer and rival GSK are going the furthest. Both companies recently reported late-stage testing in older adults. Competing vaccines are produced slightly differently, but each has proven to be very effective, especially against fatal disease. Both companies plan to seek regulatory approval in the US later this year, as well as in other countries.

McLellan, who has been closely monitoring vaccine development, said the older adults’ data “looks amazing”. “I think we’re on the right track.”

And if vaccination of pregnant women is successful, it could be “a win for two individuals instead of just one,” by providing protection for both mother-to-be and baby, Dr. Wilbur Chen of the University of Maryland School of Medicine.

Pfizer’s maternal vaccine is the same formulation it has successfully tested in older adults – and it also plans to seek Food and Drug Administration approval for those vaccines. please by the end of this year.

The new study included 7,400 pregnant women in 18 countries, including the United States, and spanned multiple RSV seasons. Preliminary results reported Tuesday suggest the vaccine is most effective for severe disease. For milder disease, the efficacy was 51% to 57% – low compared to the study’s statistical requirements but an outcome that Pfizer still calls clinically significant because it could mean fewer trips to the hospital. more doctor’s office.

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