In recent weeks, children’s hospitals in the United States have sounded the alarm. Their beds are full of young patients who have difficulty breathing and urgently need oxygen. This year, the culprit is not the coronavirus, but the respiratory syncytial virus, better known as RSV.
RSV is not a new pathogen. Worldwide, approximately 64 million people become infected with the virus every year. The virus poses a particularly high risk to adults over the age of 65 and children. They need to be hospitalized more often. Worldwide, RSV leads to approximately 160,000 deaths each year, including more than 100,000 children under the age of five. There is still no vaccine against the disease or a general treatment available.
But solutions are on the way. Experts say monoclonal antibody treatment against RSV could be approved by the end of the year. And a vaccine could potentially be rolled out in time for the 2023 RSV season. Pfizer said on Nov. 1 that its vaccine is 81 percent effective in the first 90 days of an infant’s life and 69 percent effective in the first six months of life. The company aims to submit an application for approval for its vaccine candidate against RSV by the end of 2022.
“This could bring about a huge change worldwide,” says Keith Klugman. He is the director of the pneumonia (pneumonia) program at the Bill & Melinda Gates Foundation that funds Pfizer’s vaccine candidate.
Here’s what you need to know about RSV, why the number of cases is currently so high in the US and why these new developments are so promising, according to experts.
What is RSV?
The U.S. Centers for Disease Control and Prevention describes RSV as a respiratory virus that is spread primarily through coughing, sneezing, and other forms of close contact. It is also seasonal. In the US, RSV is worst in the winter months. Anyone can contract or spread RSV. People with a healthy immune system usually only have mild cold symptoms.
Older adults with weakened immune systems have a harder time fighting off the virus. This also applies to young children. Their immune system is still developing and has not been exposed to the pathogen before. They are more likely to have a serious RSV infection. Symptoms include dehydration and difficulty breathing.
“Before corona arrived, RSV was clearly the leading cause of serious respiratory disease in infants and young children.” So says Kathleen Neuzil, director of the Center for Vaccine Development and Global Health at the University of Maryland School of Medicine. Young children are also particularly vulnerable because their airways are narrow. In children under one year of age, RSV is the leading cause of bronchiolitis. Then the smallest airways in the lungs (bronchioles) are inflamed.
Why is the number of cases increasing?
It is not uncommon for there to be so many cases in an RSV season in the US. It’s a bit unusual for RSV to show up so early in the year. Neuzil suspects that corona is to blame. “Corona has significantly disrupted the seasonality of our respiratory viruses,” she says. Now that many people no longer wear masks regularly, experts hypothesize that the viruses have started circulating out of season. For the simple reason that people are more vulnerable to an infection after they have not been sick for two years.
According to Neuzil, it is unclear whether this change is permanent or if RSV will eventually return to its seasonal pattern. This starts in mid-September, but peaks from late December to mid-February. It also remains to be seen whether the current peak is the true peak of this year’s RSV season or if the worst is yet to come.
Why is there no vaccine against RSV yet?
Researchers have been trying to prevent death from RSV for decades. An attempt in the 1960s to develop a vaccine ended in colossal failure. Children were not protected by it, but were made sick by it.
Bill Gruber, senior vice president of Vaccine Clinical Research and Development at Pfizer, says that’s when it became clear that a different approach was needed. The protein that allows the virus to fuse with the membrane of a human lung cell had to be attacked.
According to Gruber, the fundamental breakthrough came in 2013. Scientists then discovered that they needed to stabilize the virus protein in the vaccine so that it would retain its prefusion form. That’s the idea behind most of the treatments currently being developed.
What new treatments against RSV are in development?
The most advanced RSV treatment is Nirsevimab. This is a monoclonal antibody developed by AstraZeneca. Nirsevimab is given to babies by injection at birth or shortly afterwards. It directly delivers RSV antibodies into the bloodstream, allowing the immune system to neutralize the virus and prevent it from multiplying.
In March, a Phase III clinical trial found that the vaccine offers infants 75 percent protection against lower respiratory tract infections, which are so severe that medical treatment is required. In early October, the World Health Organization’s Strategic Advisory Group of Experts on Immunization (SAGE) reviewed the data from the clinical trial and reported that regulatory approval is “imminent.”
Neuzil, a member of SAGE and the technical advisory group for RSV vaccines, says the U.S. Food and Drug Administration may approve the treatment by the end of 2022.
What About RSV Vaccines?
Several RSV candidate vaccines are in development, according to Neuzil. But the first likely to make it to the finish line is Pfizer’s vaccine for pregnant women. The idea behind this vaccine is to protect babies before they are even born. This is done by vaccinating the mother, who then produces antibodies that are passed on to the fetus via the blood.
In April, a Phase IIb clinical trial found that Pfizer’s vaccine produced high levels of antibodies, making it a breakthrough therapy by the FDA. That means the agency wants to accelerate development and evaluation of the vaccine. On Nov. 1, Pfizer said positive results from the Phase III trial mean the company can now complete the study and apply for approval. According to Klugman of the Gates Foundation, the FDA will give approval in 2023.
“This is something I’ve looked forward to my entire professional life,” Gruber says. “We’re making the right kind of antibodies, so I think we can succeed in our set-up in a really good way.”
Meanwhile, early results from Pfizer’s phase III study in older adults showed 85% efficacy. And a host of other RSV candidate vaccines aren’t far behind. Some of these candidates contain adjuvants. These are excipients that enhance the immune response and which, according to Neuzil, should not be used during pregnancy.
That’s great, but how can you protect people?
Neuzil: ‘What we’re seeing now with the new RSV vaccines and the antibodies is very interesting, but it won’t help babies this winter.’ She advises people to continue to take precautions, such as wearing masks. Especially if they are around newborns or elderly people who are especially vulnerable to severe RSV.
“We’re getting close, but we’re not there yet this year,” she says. “So it’s really important to be very careful.”
Editor’s Note: This story was originally published on October 27, 2022. It has been updated to reflect the results of Pfizer’s Phase III clinical trial of Pfizer’s maternal vaccine candidate.
This article was originally published in English on nationalgeographic.com