Scientists win over RSV, a persistent threat to children

Of the three respiratory viruses Americans face this winter, two — the coronavirus and the flu — are well-known threats. The third, respiratory syncytial virus, which has already sent thousands of children to hospitals, is a mystery to many.

For pediatricians, however, RSV is all too familiar. It is one of the leading causes of infant death worldwide and particularly dangerous for babies born prematurely.

Worldwide, RSV resulted in an estimated 3.6 million hospitalizations in 2019 and more than 100,000 deaths of children under 5, mostly in poor countries.

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“It’s, unfortunately, one of those big killers that nobody knows about,” said Dr. Keith Klugman, who directs the pneumonia program at the Bill & Melinda Gates Foundation.

“You survive RSV if you have access to care, respiratory support and oxygen,” he added. “Without these, babies will die.”

The virus also poses special risks for pregnant women, immunocompromised children and adults, and adults over 65. No vaccine or treatment is available. But after decades of stalled progress, more than 30 preventative options are on the horizon, including nine in advanced testing.

On Tuesday, Pfizer announced that its RSV vaccine had been shown to be 82% effective against hospitalization in infants under 90 days old, and 69% in those under 6 months old.

The vaccine has not met the Food and Drug Administration’s threshold to prevent doctor visits, but the company plans to submit its vaccine for approval before the end of the year.

In October, GSK reported that its RSV vaccine was 83% effective against severe disease in adults over 60. The vaccine is under review by regulatory agencies in Europe and Japan, and the FDA is expected to begin its review by the end of the year. .

Pandemic restrictions have kept RSV mostly at bay for the past two years. But this year, seriously ill RSV children are filling hospitals weeks earlier than usual. More of these young patients are sicker than those seen before the pandemic because they had developed weak immunity against RSV.

Babies who survive RSV infection may experience lung damage, making them more susceptible to pneumonia. Much of the damage comes from the consequences of the infection, rather than the infection itself.

Most older children and adults are exposed to RSV several times during their lifetime, and the immunity they acquire prevents serious illness and even infection. Doctors have only recently started testing adults for RSV, leading to the realization that in some years RSV infections can rival those caused by the flu.

“We just don’t appreciate it as much because the diagnostics aren’t as available yet as they are for COVID or the flu,” said Dr. William Schaffner, an infectious disease physician at Vanderbilt University Medical Center in Nashville, Tennessee. .

In the elderly, RSV causes approximately 14,000 deaths per year. Recognition of the scale of the problem is partly responsible for pharmaceutical companies’ willingness to develop vaccines.

RSV was identified in the 1950s and attempts to develop a vaccine began in the 1960s, but researchers were stalled for decades. The field was further pushed back when a candidate vaccine appeared to increase the risk from the virus.

A technical discovery in 2013 at the National Institutes of Health revived the field, allowing scientists to design powerful vaccines. In its trial, GSK’s vaccine was about 94% effective against serious illness in adults 70 to 79 years old or those with underlying medical conditions.

“We think we have a vaccine that can really be a very important solution to preventing severe RSV-associated respiratory disease in the elderly,” said Dr Phil Dormitzer, who leads vaccine development at GSK.

Several research teams are working on vaccines for young children. A group, led by Dr. Coleen Cunningham, chief pediatrician at Children’s Hospital of Orange County and chairman of the department of pediatrics at the University of California, Irvine, is developing a nasal vaccine containing a weakened version of the virus to children 6 -24 months of age.

“The advantage of that is that it’s not a shot, so you don’t have to worry about needles,” Cunningham said. The vaccine would elicit antibodies in the nose, where the virus enters, rather than in the blood and could thus more effectively prevent infection.

Researchers are trying to find a balance in which the virus is too weak to cause symptoms and yet strong enough to produce a robust immune response. The results so far are promising, Cunningham said.

In the youngest babies, who are most at risk, vaccines do not have enough time to develop sufficient immunity. An alternative is to give babies a monoclonal antibody – a lab-made version of a powerful antidote to the virus – which can prevent infection.

One such antibody, Synagis, was approved in 1998 and is injected once a month into infants born after 32 weeks’ gestation or less, or those with heart or lung problems that increase their risk. In trials, the antibody reduced hospitalizations due to RSV infection by 55%.

But Synagis is rarely used because its price is prohibitive, Cunningham said.

Newer monoclonal antibodies may last longer and cost less. A committee of the European Medicines Agency has recommended approval of a single dose of Beyfortus, made by Sanofi and AstraZeneca, to protect children against RSV for an entire season.

Another alternative to protect infants is to vaccinate pregnant women. Antibodies from the mother can cross the placenta to the fetus, research shows, protecting the baby for the first few months after birth.

In the Pfizer trial, approximately 7,400 pregnant women received a single dose of the experimental RSV vaccine or a placebo between the end of the second and third trimesters. The researchers followed the women’s health for six months after giving birth and the infants for at least a year.

The trial covered 18 countries and several RSV seasons in the northern and southern hemispheres. Klugman of the Gates Foundation said he hopes the vaccine will “roll out very, very quickly” and be available even in poor countries by 2024.

Some companies are testing the simultaneous administration of RSV and influenza vaccines and have found so far that neither seems to interfere with the other. Others are working to extend the protection time of an RSV vaccine.

The scale of RSV cases this year underscores the urgent need for vaccines and could serve to convince parents to vaccinate their children once vaccines become available, experts said.

“Ironically, perhaps, if these outbreaks have any useful purpose, it will be to raise awareness about RSV,” Klugman said, “so that when vaccines arrive, women will have an enthusiastic opportunity to protect their babies.”

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