In other developments, the CDC reported one more pediatric flu death, raising the season's total to 281, the highest for a nonpandemic year.
Among those not treated, 2,535 had RSV-associated admissions, compared with 850 in the treated group.
The preventive drug was 84% effective in preventing RSV-associated hospital care.
Death rates among hospitalized patients were 8.9% to 10.4%, and annual adjusted costs were $32 million to $90 million, mainly driven by ICU care.
The WHO lowered its assessment from high to medium, based on several factors, including high population immunity and improved clinical management.
Ongoing monitoring of vaccine effectiveness during subsequent seasons is needed to more fully characterize waning of protection and inform revaccination intervals, the authors say.
The findings strengthen the evidence supporting universal RSV immunization in children, the authors say.
Test positivity is down slightly, but emergency department visits for COVID are elevated in children.
The authors say the findings support RSV vaccination of older Americans.
The recommended vaccines are against COVID-19, influenza, RSV, pneumonia, and shingles.
