Efficacy and safety of a fourth dose of the COVID-19 vaccine in kidney transplant recipients: A systematic review and meta-analysis

BACKGROUND: Kidney transplant recipients (KTRs) who become infected with SARS-CoV-2 are at greater risk of serious illness and death than the general population. To date, the efficacy and safety of the fourth dose of the COVID-19 vaccine in KTRs have not been systematically discussed. METHODS: This systematic review and meta-analysis included articles from PubMed, Embase, the Cochrane Library, Web of Science, China National Knowledge Infrastructure, and Wanfang Med Online published before May 15, 2022. Studies evaluating the efficacy and safety of a fourth dose of the COVID-19 vaccine in kidney transplant recipients were selected. RESULTS: Nine studies were included in the meta-analysis, with a total of 727 KTRs. The overall pooled seropositivity rate after the fourth COVID-19 vaccine was 60% (95% CI, 49%–71%, I(2) = 87.83%, p > 0.01). The pooled proportion of KTRs seronegative after the third dose that transitioned to seropositivity after the fourth dose was 30% (95% CI, 15%–48%, I(2) = 94.98%, p < 0.01). CONCLUSIONS: The fourth dose of the COVID-19 vaccine was well tolerated in KTRs with no serious adverse effects. Some KTRs showed a reduced response even after receiving the fourth vaccine dose. Overall, the fourth vaccine dose effectively improved seropositivity in KTRs, as recommended by the World Health Organization for the general population.