As a virus leaves some babies under the age of two wheezing — adding to the pressure on Canada's hospitals — drug makers are working on new treatment and vaccine options for the illness.
Respiratory syncytial virus, or RSV, gets the "S" in its name for large cells known as syncytia that form when infected cells fuse. Syncytia are prone to die off and plug up airways, leading to respiratory distress, Dr. Clement Lee, a pediatrician at Newton-Wellesley Hospital in Newton, Mass., said in a recent Twitter thread.
For most healthy people, though, the highly contagious virus feels like an ordinary cold.
Dr. Rod Lim, medical director for the pediatric emergency department at Children's Hospital in London, said while many infants weather RSV just fine, the virus tends to present in young children almost like asthma, with wheezing.
Before the COVID-19 pandemic, children were commonly exposed to RSV between November and March. By two years of age, it's estimated 90 per cent of us have been infected.
But this year, RSV arrived early in parts of Canada and the U.S., based on swabs of those in the hospital — it even circulated in the summer.
"We're seeing viruses circulate at different times than we have," Lim said at a virtual briefing hosted by the Ontario Medical Association.
"It's a little bit of a perfect storm right now."
Lim's emergency department was built for about 100 visits a day, and on Tuesday, there were 280 visits, forcing staff to look for alternate spaces to care for people, he said.
Staffing challenges and supply chain issues for medications to reduce pain and fever are adding to the burden, he added.
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"If I had an ideal world, [it] would definitely not allow babies to get RSV and to get any kind of infections for the first two to three months," Lim said.
Eram Chhogala, a registered nurse working in emergency rooms in the Greater Toronto Area, said she's seeing families show up with multiple children needing treatment.
"We're talking whole families of four, maybe even six," Chhogala recalled in an interview. "You have, say, for example, three kids all with cough and fever. Three patients that require treatment for a fever."
When the parents are asked if they gave Tylenol or Advil, they say, "Sorry, we couldn't, because there was nothing left and we tried going everywhere," the nurse said.
What's more, RSV is circulating at the same time as the flu, COVID-19 and common cold viruses like rhinovirus and enterovirus are giving people fever, cough and other symptoms.
Why infants are most vulnerable
Dr. Jesse Papenburg, a pediatric infectious diseases physician at the Montreal Children's Hospital of the McGill University Health Centre, said infants are particularly vulnerable to respiratory infections. In part, that's because airways and thoracic or chest muscles get stronger as they grow.
"The risk of the virus getting down into the lower respiratory tract is always greatest during your first infection" with RSV, Papenburg said in an interview. "The way your body can handle that lower respiratory tract infection is very different when … you're two years old versus when you're two weeks old."
Papenburg said his hospital is also extraordinarily busy with a surge in respiratory viruses, which adds to wait times. As well, elective surgeries get cancelled to free up staffed beds in intensive care and elsewhere.
The positivity rate for RSV was above 25 per cent last month, which he called extremely unusual.
Treatment pipeline opens
Infants are born susceptible to RSV because they don't have antibodies to fight off the infection, Papenburg said.
Drug maker GSK is developing a vaccine program for pregnant individuals as well as older adults, an age group Papenburg said is also now considered at risk for complications from RSV.
Moderna said it plans a Phase 3 clinical trial of an mRNA vaccine for adults aged 60 and older.
Potential RSV vaccines from other companies are also in the works.
Vaccinating pregnant individuals could help protect infants, Papenburg said. That's why pertussis (or whooping cough) vaccines are given in pregnancy, and the antibodies cross the placenta.
Earlier this month, Pfizer announced Phase 3 clinical trial results for its RSV vaccine candidate in a press release. The vaccine is given in pregnancy with the aim of protecting the infant.
Currently, those hospitalized for RSV receive supportive care for what brought them in, like dehydration or oxygen through a mask to ease their breathing.
Babies at high risk of RSV complications can be given monthly shots of a costly treatment called palivizumab during the regular RSV season. Some provinces and territories started rolling it out early this year.
Last week, drug makers Sanofi and AstraZeneca announced that the European Commission authorized a one-dose RSV drug called nirsevimab. It's a laboratory-developed antibody designed to protect infants during their first exposure to RSV.
"You can give that one shot and the baby has protective levels of antibodies for the whole RSV season," Papenburg said. "What the studies have shown is that it protects as well as palivizumab in terms of preventing hospitalizations" in both high-risk patients as well as otherwise healthy term infants.
The likely catch? Price.
"I think one of the big questions will be is, what will be the cost?" Papenburg said. "How much are we willing to pay to avert these hospitalizations due to RSV?"
Immunization advisory committees like NACI will likely be considering use of nirsevimab in all infants, said Papenburg, who reports potential conflicts of interest in the last 36 months from several drug makers, including AstraZeneca.