(Bloomberg) -- Covid-19 hospitalizations are rising among babies under 6 months old, and the US Centers for Disease Control and Prevention is urging mothers to get vaccinated to reduce the risk of infection in those not yet eligible for shots, Director Rochelle Walensky said. 

“We’re seeing more and more of those younger babies getting hospitalized,” Walensky said in an exclusive interview at CDC’s headquarters in Atlanta. “That’s really where we’re trying to do some work now because we think we can prevent those by getting mom vaccinated.” 

Walensky, who just recovered from a Covid-19 infection and subsequent post-treatment rebound, spoke in advance of the release of an agency report that examines an increase in the rate of hospitalizations among infants. The infectious disease expert said that in recent months, children younger than 6 months old have faced the second-highest rate of hospitalization across all age groups, trailing only behind those ages 65 and up.

Hospitalizations increased eleven-fold for those infants from December 2021 to August 2022, during the time when omicron and its subvariants were dominant, according to a study published Thursday in CDC’s Morbidity and Mortality Weekly Report. Hospitalization rates peaked in late July, when the BA.5 strain accounted for the majority of US infections, the study said.

Average weekly hospitalization rates for babies younger than 6 months were similar to adults between the ages of 65 and 74, according to the study. But while the elderly and people with weak immune systems remain at highest risk of Covid hospitalization, they can get vaccinated, unlike the very youngest patients. 

“To help protect infants too young to be vaccinated, prevention should focus on nonpharmaceutical interventions and vaccination of pregnant women, which might provide protection through transplacental transfer of antibodies,” the study says.

Publicly available CDC data show hospitalizations of children under 5 years of age have remained persistent throughout the pandemic, rising during big waves of the virus. In the week ending Oct. 29, 46 children under 5 were hospitalized with Covid-19, the CDC said, more than double the number of kids aged 5 to 17. 

The CDC is preparing to encourage pregnant people to receive the new bivalent Covid vaccines that protect against two highly infectious omicron strains, BA.4 and BA.5. “We know that those antibodies will transfer to the baby,” Walensky said. “It’ll actually help protect the infant.” 

One study showed that when pregnant women had two doses of an mRNA Covid vaccine, the kind made by Pfizer Inc. and Moderna Inc., there was a reduction in the risk of hospitalization with Covid for babies under 6 months of age.

Uptake of Pfizer and Moderna’s bivalent shots has been strikingly low among adults so far, with only about 5% of those between the ages of 24 and 49 having received the new boosters, Walensky said. The CDC will seek to reinvigorate the effort to vaccinate all eligible children 6 months and older. 

“We have seen relatively low vaccination rates in our 6 months to 5-year-olds, even our 5-to-11 and our 12- to 17-year-olds,” she said. “One of the most important things that you can do is to get your children vaccinated.”

Other threats

Covid isn’t the only threat young children face this fall and winter. US health-systems and children’s hospitals are currently grappling with a wave of respiratory viruses, including influenza and respiratory syncytial virus, or RSV. 

“We are right now seeing a lot of RSV earlier in the season than we normally would and probably more hospitalizations related to the fact that there were several years’ worth of children who didn’t get that exposure,” Walensky said. 

Read More: Flu, Covid and RSV Are on the Rise and Already Burdening Hospitals

Though RSV immunizations haven’t yet been approved by regulators, a recent study from Pfizer, which has an experimental candidate in development, suggests that vaccinating pregnant people against RSV can protect their newborns from infection. 

Until an RSV shot is available, Walensky said, masking and improving indoor ventilation will help prevent the spread of disease among children. Already in the Southeast, the CDC is seeing RSV-related hospitalizations begin to decline. 

The latest Covid, RSV and influenza strains that caused an early surge in pediatric cases don’t appear to result in more severe disease, Walensky said. The wave of infections is more likely a reflection of children’s naive immune systems after years of masking and social distancing due to the pandemic, she said.

--With assistance from Madison Muller.

(Updates with CDC study starting in fourth paragraph.)

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