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Around the country, pediatric hospital wards are filling up with young children fighting a virus few adults know much about.
Respiratory syncytial virus, which infects nearly everyone by the age of 2, usually goes unnoticed because it mostly causes a common cold.
But RSV is a leading cause of hospitalizations among newborns and young children; 58,000 in a typical year.
“A lot of parents who come into the hospital and their babies are really sick with it tell me ‘I had no idea this even existed. I had no idea my baby could get so sick from this,’” said Dr. Elizabeth Schlaudecker, medical director of the division of Infectious Diseases at Cincinnati Children’s.
RSV also strikes at the other end of life, causing more than 177,000 hospitalizations and 14,000 deaths among older adults annually.
Despite decades of effort, the arsenal to fight RSV has so far included only one monoclonal antibody, given monthly to children at high risk for severe disease. There has never been a way to prevent RSV.
But six drug companies are actively developing RSV vaccines or antibodies, suggesting this year could be the last one without adequate tools to fight the virus.
“We’re experiencing a new hope that the RSV landscape is going to dramatically change, especially in the very young infant, in the next year or so,” said Dr. Octavio Ramilo, chief of infectious diseases at Nationwide Children’s Hospital in Columbus, Ohio.
On Tuesday, drug giant Pfizer announced results from a Phase 3 clinical trial showing its experimental RSVpreF vaccine protected infants when given to pregnant participants between 24 and 36 weeks of gestation.
Through the first 90 days of a baby’s life, the vaccine was more than 80% effective at preventing severe illness. At six months, it remained nearly 70% effective, the study showed. The trial did not raise any major safety concerns for either parent or child.
Pfizer plans to submit an application to the Food and Drug Administration by the end of the year, potentially allowing its vaccine to reach the public before next year’s RSV season, which typically starts in late October.
Earlier this year, Sanofi Pasteur and AstraZeneca also showed protection against severe disease with their antibody nirsevimab, though the trial, disrupted by COVID-19 lockdowns, failed to show a stastically significant reduction in the risk of hospitalization from RSV.
Antibodies can provide protection when an infant’s immune system is too immature to benefeit from a vaccine, said Jon Heinrichs, Sanofi’s global head of Innovation and Emerging Sciences.
“The majority of hospitalization and severe disease caused by RSV happen in that first year of life,” he said. “It’s critical to protect these infants.”
About 70% of children contract RSV before their first birthday and 90% by their second. It’s impossible to tell ahead of time which children will have a simple, mild case and which few will become severely ill, requiring hospitalization to help them breathe.
The disease is usually less severe in children older than 6 months, but RSV has been particularly bad this fall, experts say, because the precautions taken during earlier days of the pandemic protected babies against RSV in addition to COVID-19.
Now, three years’ worth of children are getting exposed to RSV for the first time, with a fraction suffering severe consequences.
Why new approaches are coming now
Tools to fight RSV have been a long time coming.
“Pediatricians and pediatric infectious disease doctors have fought RSV for decades and honestly not made a lot of progress,” Schlaudecker said. “It seems long overdue that we have an effective vaccine.”
Research into RSV vaccines was tabled for decades after two children died in a 1967 trial, which concluded the experimental vaccine actually made the disease worse.
In 2013, researchers from the National Institutes of Health discovered a way to stabilize the protein that was the vaccine’s target. (The same idea was used in COVID-19 vaccines, which also proved extremely effective.)
Ever since, companies have been working on RSV prevention tools, many of which are coming to fruition at the same time.
“Out of the blue, instead of preventing (RSV) in a very small group, we can give it to all children,” Ramilo said. This is important because 80% of children who develop severe RSV had no obvious risk factors. Worldwide, RSV is the second-most common cause of death in the first year of life, after malaria.
Having vaccines, which are inexpensive and easy to administer, as well as monoclonals will be useful, Ramilo said. Monoclonals might provide protection until a child is old enough to get a vaccine for themselves.
“Both strategies have their role and their benefit,” he said. “Having more than one is always good.”
Preventing that first serious respiratory infection might also pay off later in life, said Dr. Alejandra Gurtman, vice president of vaccine R&D for Pfizer.
“If you’re able to avoid that damage that you have from the first infection, you may be able to have healthier lungs,” potentially avoiding problems like asthma later on, she said.
Other approaches to RSV
Johnson & Johnson and GlaxoSmithKline are developing their own RSV vaccines for older adults, Moderna is developing one for children and 60+ adults and Vir Biotechnology is developing a monoclonal antibody to treat people at high risk for severe RSV.
GSK’s vaccine, AReSVi 006, was shown this summer to reduce severe RSV in older adults by 94%, according to a 25,000-person phase 3 trial. The shot also had a favorable safety profile, according to the company, and could be administered along with a flu shot. FDA approval could come as soon as later this year.
Moderna is six months behind other companies, CEO Stéphane Bancel said in a September interview, but expects this month to have safety data for the first 6,000 trial participants six months after their shot. Depending on infection rates, the company will have an interim analysis some time in the winter or spring, he said.
In adults over 60, immunity they may have gained against RSV in childhood wanes. Ailments such as lung disease increase vulnerability and the immune system naturally weakens with age.
It’s unclear whether RSV vaccines in older people would be needed every year. If so, it’s possible that the shot could be combined with a flu and COVID-19 vaccine, said Sanofi’s Heinrichs, whose company is developing an RSV vaccine in addition to its antibody.
In August, Pfizer announced a single dose of RSVpreF was effective at preventing severe disease in adults 60 and older. The study of more than 37,000 people showed the vaccine was well-tolerated, with no safety concerns.
Sanofi and AstraZeneca are seeking regulatory approval to give the antibody to all infants entering their first RSV season as well all children who remain vulnerable in their second year, because of chronic disease. In September, the effort won the support of the European Medicines Agency’s Committee for Medicinal Products for Human Use. The companies plan to submit a licensing request to the FDA later this year.
Protecting young lives
Dr. Melissa Squires works in a pediatric intensive care unit, so she knows all too well what an infant struggling to breathe looks like.
That’s why she was thrilled when pregnant with her second daughter last year to be able to sign up for a clinical trial of Pfizer’s RSV vaccine at Cincinnati Children’s where she works.
“This was another opportunity for me to set my baby up for the best chance of being healthy both inside of me and outside of me,” said Squires, a neurocritical care specialist, treating children with strokes, seizures and traumatic brain injuries.
Squires received the shot 34 weeks into her pregnancy and her daughter Natalie was born a couple of days before Christmas. As part of the trial, she had to provide extra cord blood, allow her pediatrician to share data and answer questions by phone.
Both mother and baby got through last winter without catching any respiratory viruses, despite having an older child at home.
Being pregnant during the pandemic, Squires said, heightened her awareness about viruses and made her more eager to protect the vulnerable.
“This was one more thing I could do to protect this new life I was responsible for,” she said in the spring. “To have the peace of mind that my baby is protected from one of the biggest offenders of childhood illness is just a little bit of weight off my shoulders.”
Prevention is really the only solution to the misery of RSV, Schlaudecker said.
“If we can save lives, prevent hospitalization of infants who are the most vulnerable, we need to do that as quickly as possible.”
In newborns and babies, the bronchial tubes that go into the lung are extremely small. When they fill with fluid during an RSV infection the child can have trouble breathing and eating. “They are the ones we worry about the most,” Schlaudecker said. “Vaccinating during pregnancy is such a great, creative way to protect them.”
The range of positive trial results “are really thrilling from an RSV doctor’s standpoint,” she said. “We see a light at the end of the tunnel.”
Contact Karen Weintraub at kweintraub@usatoday.com.
Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.
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