Despite a relatively slow start to respiratory disease season, low vaccination rates threaten that trend and the rapid rise of some illnesses is already putting children at increased risk.

Overall, the US Centers for Disease Control and Prevention predicts that this season could be similar — or even better — than the last, but the peak rate of respiratory virus hospitalizations will likely be well above what they typically were in years before the Covid-19 pandemic.

For now, though, Covid-19 levels in the US are nearly the lowest they’ve been since the start of the pandemic and they’re decreasing, according to CDC data from December 2. Wastewater data suggests that flu and respiratory syncytial virus, known as RSV, are also circulating at low levels but emergency department visits for both viruses have started to rise.

There is still a lot that could change, experts say.

“Historically, we see an increase in cases about a week after Thanksgiving and how quickly they increase between then and the Christmas holidays gives us a better sense of the season,” said Dr. Andy Pekosz, a virologist at the Johns Hopkins Bloomberg School of Public Health.

Vaccination will play a key role

The potential for new Covid-19 variants factors into the CDC’s forecasts for respiratory disease season, but “vaccination is expected to play a key role in preventing hospitalizations” for flu, Covid-19 and RSV, the agency said.

Covid-19 vaccination rates are at about the same low rate they were at this time last year, CDC data shows. Fewer than 1 in 5 adults and only about 1 in 12 children has received the updated Covid-19 shot for this season.

And most adults — about 60% — don’t plan to get the updated Covid-19 vaccine, according to survey data published by the Pew Research Center last month. Most adults who don’t plan to get the shot said that they don’t think that they need it or that they’re worried about the side effects; about a quarter said that they don’t get vaccines in general.

Flu vaccination rates are also low. Only about 37% of adults and 33% of children have gotten their flu shot this season, according to data through mid-November. The flu vaccination rate among children is significantly lower than it’s been at this point in the season for the past six years, according to CDC data; the rate is nearly 12 percentage points lower than the season before the pandemic and 5 percentage points lower than last season.

“While vaccines do not always guarantee that a child will avoid illness, they generally provide enough immune support to ensure that the illness is less severe,” said Elizabeth Choma, a pediatric nurse practitioner at Loudoun Medical Group and an assistant professor at the George Washington University School of Nursing. For example, flu statistics show that most pediatric deaths from influenza occur in children who were not vaccinated against the flu.

Unique risks for children

Respiratory diseases pose unique risks to children, experts say.

“Infants, toddlers, and preschool-age children have smaller airways, which makes it more difficult for them to breathe when their airways become inflamed,” Choma said. “Additionally, infants are obligate nose breathers, meaning they rely on breathing through their nose. When they become congested, it becomes harder for them to breathe and perform everyday activities like drinking, which can increase their risk of dehydration.”

An RSV infection is typically mild for adults but infants and seniors face a higher risk of severe disease.

The test positivity rate for RSV is rising significantly faster than it is for flu or Covid-19, CDC data shows. And the hospitalization rate is rising quickly among children – there were about 3 RSV hospitalizations for every 100,000 children during the week ending November 23, twice as many as a month earlier. There were at least 21 hospitalizations for every 100,000 infants that week, up from less than 14 a month earlier. Meanwhile, the hospitalization rate for adults hasn’t risen above 0.5 so far this season.

Children’s hospitals already strained

Another respiratory disease known as walking pneumonia, caused by the bacterium Mycoplasma pneumoniae, is spreading rapidly among young children and children’s hospitals are feeling the strain.

The CDC first warned of an increase in these infections in October, and trends haven’t improved. Cases starting rising globally in 2023 after a few years of abated spread during the Covid-19 pandemic. But surveillance data from the US this year suggests that hospital visits peaked in August and have stayed elevated since – especially among children. The increase in children ages 2 to 4 is particularly notable because walking pneumonia typically isn’t a leading driver of disease for this age group, according to the CDC.

Surges in respiratory diseases can strain hospital systems and exacerbate ongoing supply chain challenges, especially busy emergency departments, said Dr. Torey Mack, chief medical officer for the Children’s Hospital Association.

Just a few weeks into the respiratory disease season, a few children’s hospitals are already feeling the impact, she said. The emergency room at Cook Children’s Medical Center in Fort Worth, Texas, for example, is nearing capacity as increases in hospitalizations for RSV and pneumonia rise.

Pediatric pneumonia cases requiring hospitalization have also spiked in central Virginia, and Dr. David Marcello, chief of pediatric hospital medicine at Children’s Hospital of Richmond at Virginia Commonwealth University said that he suspects this trend is “likely to worsen with pollen and mold counts rising, colder weather keeping everyone inside and the holidays bringing people together.”

“Children’s hospitals have learned from years past to anticipate this surge around this time of year and have the specialists needed to care for kids, particularly those younger children who are more severely impacted by this disease,” Mack said. “Because the needs based on the impacts of respiratory illnesses can increase dramatically, it is critical that children have access to the care they need and the expertise of pediatric specialists who can act quickly.”