Scientists are gaining on RSV, a constant threat to children

Scientists are gaining on RSV, a constant threat to children

Scientists are gaining on RSV, a constant threat to children

Of the three respiratory viruses Americans are battling 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.

Pediatricians, however, are all too familiar with RSV. It is the leading cause of infant mortality worldwide, and is especially dangerous for premature babies.

Worldwide, RSV led to an estimated 3.6 million hospital admissions in 2019 and more than 100,000 deaths in children under 5 years of age, mostly in poor countries.

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

“You will survive RSV if you have access to care, breathing support and oxygen,” he added. “In the absence of that, babies will die.”

The virus also poses a special danger for pregnant women, children and adults with weakened immunity and adults over 65 years of age. There is no vaccine or treatment available. But after decades of stalled progress, more than 30 preventative options are on the horizon, nine of which are in advanced trials.

Pfizer announced Tuesday that its RSV vaccine was 82% effective against hospitalization among infants younger than 90 days, and 69% among those younger than 6 months.

The vaccine did not meet the Food and Drug Administration’s threshold for preventing 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 serious disease in adults over 60. The vaccine is currently being reviewed by regulatory agencies in Europe and Japan, and the FDA is expected to begin a review by the end of the year. .

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

Babies who survive RSV infection can suffer lung damage, making them more susceptible to pneumonia. Much of the damage is due to the effects of the infection, not the infection itself.

Most older children and adults are exposed to RSV multiple times during their lifetime, and the immunity they develop prevents severe disease, if not infection. Doctors have only recently begun testing adults for RSV, which has led to the realization that within a few years, RSV infections could 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.

Among the elderly, RSV causes about 14,000 deaths per year. Recognition of the scale of the problem is partly responsible for the drive among pharmaceutical companies to develop vaccines.

RSV was identified in the 1950s and attempts to develop a vaccine began in the 1960s, but researchers were at a standstill for decades. The field further retreated when a candidate vaccine appeared to increase the risk of the virus.

A 2013 technical breakthrough 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 severe disease in adults aged 70 to 79 or those with underlying health conditions.

“We think we have a vaccine that can really be a very important solution for preventing serious RSV-related 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. One group, led by Dr. Coleen Cunningham, chief pediatrician at Children’s Hospital of Orange County and chief of pediatrics at UC Irvine, is developing a nasal drop vaccine containing a weakened version of the virus for children 6-24 months of age.

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

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

In the case of the youngest babies, who are the most vulnerable, there is not enough time for vaccines to build up sufficient immunity. One alternative is to give babies a monoclonal antibody – a lab-made version of a powerful antidote to the virus – that 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 who have heart or lung problems that increase their risks. In trials, the antibody reduced hospitalization for RSV infection by 55%.

But Synagis is rarely used because it is prohibitively expensive, Cunningham said.

Newer monoclonal antibodies may last longer and cost less. The European Medicines Agency Committee has recommended the approval of a single dose of Beyfortus, manufactured by Sanofi and AstraZeneca, to protect children against RSV throughout the season.

Another alternative for the protection of infants is the immunization of pregnant women. The mother’s antibodies can cross the placenta to the fetus, research has shown, protecting the baby for the first few months after birth.

In the Pfizer trial, about 7,400 pregnant women received a single dose of an experimental RSV vaccine or a placebo during the late second to third trimester. The researchers monitored the health of the women for six months after giving birth, and the infants for at least a year.

The study covered 18 countries and multiple RSV seasons in the Northern and Southern Hemispheres. The Gates Foundation’s Klugman said he hoped the vaccine would be “introduced very, very quickly” and available even in poor countries by 2024.

Some companies are testing RSV and flu vaccines at the same time and so far have found that neither seems to interfere with the other. Others are working to extend the duration of RSV vaccine protection.

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

“Ironically, perhaps, if these outbreaks serve a useful purpose, it will be to make RSV better known,” Klugman said, “so that when vaccines arrive, there will be an enthusiastic opportunity for women to protect their babies.”

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