Optimizing COVID-19 vaccination for older adults: superior efficacy of heterologous regimens in reducing infection and mortality rates among patients aged 80 years and older during the Omicron BA.5/BF.7 outbreak.

Publication date: Jul 02, 2026

Following the adjustment of COVID-19 control policies in mainland China, particularly during the Omicron BA. 5 and BF. 7 waves, evaluating vaccine effectiveness in individuals aged ≥ 80 years is of critical importance. This retrospective study included 2,325 hospitalized patients aged 80 years and older from four hospitals between December 9, 2022, and January 27, 2023. We assessed the associations of vaccination dose, vaccination regimen, and the interval since the last vaccination with SARS-CoV-2 infection and mortality. Univariable and multivariable logistic regression analyses were performed to adjust for baseline imbalances across vaccination groups. An exploratory NAb analysis was conducted in 138 patients with paired serum samples at admission and discharge to evaluate immune responses associated with different vaccination strategies. In the unadjusted analyses, SARS-CoV-2 infection and mortality rates decreased with increasing vaccine doses. After adjustment for age, diabetes, and hyperlipidemia, receipt of 1, 2, and 3 vaccine doses was associated with lower odds of SARS-CoV-2 infection compared with no vaccination, with adjusted ORs of 0. 644 (95% CI: 0. 445-0. 931, P = 0. 019), 0. 579 (95% CI: 0. 407-0. 823, P = 0. 002), and 0. 448 (95% CI: 0. 332-0. 607, P

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