Boosters reduce COVID-19 deaths in kidney disease
COVID-19 vaccination, especially boosters, was linked to fewer infections and fewer deaths within 30 days after infection across all levels of reduced kidney function.
*Retrospective nationwide cohort; Level 2b (OCEBM).

Citation

Carlson N, Michalik F, Gerds T, et al. SARS-CoV-2 Vaccine Effect on Risk of Infection and Subsequent Outcomes in Patients with Chronic Kidney Disease. Journal of General Internal Medicine. 2025;41(8):2227–2236. doi:10.1007/s11606-025-10033-7.

Background

People with reduced kidney function have higher risk of severe illness and death after COVID-19, but vaccine benefits outside kidney failure were uncertain.

Patients

982,047 Danish adults (≥18 years) with a recent kidney filtration lab value ≤90 mL/min/1.73 m². Excluded: people without a qualifying kidney lab value; rapid antigen test results were not included.

Intervention

COVID-19 vaccination (2 doses) and booster (3rd dose), counted starting 14 days after the dose.

Control

No COVID-19 vaccination.

Outcome

Lab-confirmed COVID-19 infection; death within 30 days after a positive test.

Follow-up Period

February 2021 to June 2022; death followed for 30 days after infection.

Results

Across variant periods, vaccinated and booster-vaccinated people generally had lower infection rates. Booster vaccination was associated with lower 30-day death risk after infection across kidney function groups.
Kidney filtration group (mL/min/1.73 m²) 30-day death risk: unvaccinated 30-day death risk: booster Absolute risk reduction NNT to prevent 1 death
≥601.8%0.4%1.4%72
45–597.2%1.5%5.7%18
30–4415.8%3.4%12.4%9
<3022.9%6.0%16.9%6
Dialysis13.5%2.8%10.7%10
Analyses were adjusted and standardized mainly for age, sex, and calendar period.

Limitations

Observational design cannot prove cause and effect; vaccinated and unvaccinated groups may differ in exposure risk and testing behavior. Only people with kidney lab measurements were included, and ethnicity data were unavailable. Rapid antigen tests were not captured. Outcomes were short-term (30 days).

Funding

None reported; authors declared no conflicts.

Clinical Application

Reinforces current practice: strongly encourage COVID-19 vaccination and boosters in all patients with reduced kidney function, with greatest absolute benefit in advanced kidney disease.