The protection of CoronaVac against the infection of wild‐type SARS‐CoV‐2 (WH‐09) or Omicron variant in nude‐hACE2 mice

BACKGROUND: Immunocompromised individuals have an increased risk of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection and severe outcomes, but we pay less attention to these people. Athymic nude mice are a murine strain with a spontaneous deficiency of the Foxn1 gene, which can result in thymic degeneration or its absence, leading to immunosuppression and a decrease in the number of T cells, and are widely used in preclinical evaluations of disease in immunocompromised populations. METHODS: We investigated the protection of the coronavirus disease 2019 (COVID‐19) inactivated vaccine (CoronaVac) against the infection of wild‐type SARS‐CoV‐2 (WH‐09) or Omicron variant utilizing a hybrid‐type nude‐hACE2 mouse model. RESULTS: Compared with nude‐hACE2/W mice, the viral load in the brain and lung tissue of nude‐hACE2 mice (nude‐hACE2/WV) infected with WH‐09 after vaccination significantly decreased, and the histopathological changes were also reduced. The viral load in the brain and lung tissue of nude‐hACE2 mice (nude‐hACE2/OV) infected with the Omicron variant after vaccination was lower than that in nude‐hACE2/O, but histopathological symptoms did not improve significantly. CONCLUSION: CoronaVac provides some protection against infection of both WH‐09 and the Omicron variant in the nude‐hACE2 mice. Our findings aimed to provide a reference for vaccination against SARS‐CoV‐2 in immunocompromised populations.