COVID-19 hospitalization rates among U.S. children and adolescents rose nearly fivefold from late June to mid-August as the Delta variant became dominant, while unvaccinated adolescents ages 12 through 17 were hospitalized at more than 10 times the rate of their fully vaccinated peers, according to new federal data released Friday. The findings arrive as schools reopen across the country and sharpen the distinction between two realities of the current surge: children remain less likely than adults to suffer severe COVID-19, but the number of pediatric infections and hospital admissions is rising as community transmission accelerates.

A new Centers for Disease Control and Prevention analysis using COVID-NET surveillance found that the weekly hospitalization rate for children and adolescents ages 0 through 17 increased from 0.3 per 100,000 during the week ending June 26 to 1.4 per 100,000 during the week ending Aug. 14. Among adolescents ages 12 through 17 during June 20 through July 31, the cumulative hospitalization rate for unvaccinated patients was 10.1 times the rate among fully vaccinated adolescents.

Delta raises the volume of pediatric disease

The rise in admissions tracks the rapid spread of the Delta variant rather than evidence that children suddenly face the same clinical risk as older adults. The CDC report found that the proportions of hospitalized children experiencing severe outcomes—including intensive-care admission, invasive mechanical ventilation and death—did not differ significantly between the pre-Delta period and the period of Delta predominance. In other words, the surge is putting more children into hospitals primarily because far more infections are occurring, not because the available surveillance data show that every pediatric infection has become more severe.

A second CDC study released Friday examined national emergency-department visits and hospital admissions among children and adolescents. It found that pediatric COVID-19 cases, emergency visits and hospital admissions increased during June through August as Delta became the dominant U.S. strain. During a two-week period in August, emergency-department visits and hospital admissions were higher in states with lower overall vaccination coverage, reinforcing the importance of community vaccination in reducing the amount of virus circulating around children who are too young to be vaccinated.

The pattern is especially important for children under 12, who are not yet eligible for any COVID-19 vaccine in the United States. Their protection depends heavily on reducing exposure through vaccinated adults and adolescents, masking in high-transmission settings, staying home when ill, testing and other layered measures.

Vaccination creates a visible divide among teenagers

The 10.1-to-one hospitalization gap among adolescents provides one of the clearest pediatric measures yet of vaccination’s effect during the Delta period. Pfizer-BioNTech’s vaccine has been authorized for children ages 12 through 15 since May and remains available for everyone 12 and older. The new hospitalization data show that vaccinated teenagers are not merely less likely to test positive; they are substantially less likely to reach the hospital.

The finding comes as pediatric cases are increasing quickly. An Aug. 30 report, citing the American Academy of Pediatrics and Children’s Hospital Association, said more than 500,000 child COVID-19 cases were reported over three weeks in August, including 203,962 in the week ending Aug. 26. The totals reflect broad community transmission at a moment when millions of students are returning to classrooms.

The CDC’s hospitalization surveillance also makes clear that vaccination cannot yet protect every age group directly. Children younger than 12 remain dependent on the immunity of the people around them and on infection-control practices in schools, households and other settings. That places adult vaccination rates and school prevention policies into the same pediatric-health equation.

School outbreaks show how quickly classroom exposure can spread

An outbreak in Marin County, California, illustrates the risk when multiple safeguards fail at once. In a CDC report published Aug. 27, an unvaccinated elementary-school teacher who had symptoms continued teaching for two days and at times read aloud to students without a mask. Twelve of 22 tested students in the classroom were infected, producing a 50% classroom attack rate. Among students seated in the two rows closest to the teacher, the attack rate reached 80%.

The outbreak does not mean every school will experience that pattern. It does show how Delta can exploit close indoor contact when an infectious person is unvaccinated and masking is inconsistent. The same investigation documented infections among other students and household contacts, underscoring that school transmission can extend into families and the wider community.

CDC’s Sept. 3 COVIDView summary points to vaccination of eligible students and staff, universal indoor masking, testing, ventilation and keeping symptomatic people home as complementary measures. The agency’s position is that no single intervention is sufficient when community transmission is high.

Hospital pressure varies sharply by vaccination coverage

The geographic pattern matters because pediatric hospitals serve communities with very different vaccination rates and epidemic conditions. The second CDC analysis found higher pediatric emergency-department and hospital-admission rates in states with lower vaccination coverage during the late-August period studied. That association does not prove that state vaccination levels alone determine pediatric outcomes; transmission intensity, prior infection, behavior, demographics and local mitigation also differ. But it is consistent with a basic mechanism: when fewer eligible people are vaccinated, more virus circulates and children face more opportunities for exposure.

A Sept. 3 Washington Post account highlighted the CDC finding that unvaccinated adolescents were being hospitalized at roughly 10 times the rate of fully vaccinated adolescents. The report arrives amid concern from pediatric clinicians in hard-hit regions that sustained transmission can strain children’s hospitals even when the individual risk to most children remains lower than the risk to older adults.

A contemporaneous Fox 5 New York report similarly summarized the nearly fivefold rise in pediatric hospitalization rates and noted particularly sharp increases among young children during parts of the Delta surge. Because children under 12 cannot yet be vaccinated, clinicians and public-health officials are emphasizing measures that reduce the probability that the virus reaches them in the first place.

The data complicate claims at both extremes

The new evidence does not support the claim that COVID-19 is uniformly harmless to children, nor does it show that pediatric infections generally carry the same risk as infections in older adults. Severe outcomes remain uncommon relative to adult disease, but a low individual risk multiplied across a large wave of infections can still produce substantial numbers of emergency visits and hospitalizations.

The most actionable finding is the gap among vaccine-eligible adolescents. Vaccination is associated with dramatically lower hospitalization rates at the same time Delta is driving more pediatric disease overall. For younger children, the immediate strategy remains indirect protection: lowering community transmission, reducing exposure in schools and homes, and using layered prevention until a vaccine is authorized for their age groups.

As the school year begins, the question is no longer whether children can be affected by the Delta surge. The federal data show that they already are. The public-health challenge is to keep a rise in infections from becoming a larger rise in severe disease by using the tools currently available—especially vaccination for everyone old enough to receive it.