Fig 2.

Neutralizing antibody responses to different PHE-CoV vaccines. Blood was obtained from the tail veins of group 1 mice at 2, 4, and 6 weeks, and the sera were used to detect VN antibodies; titers are expressed as log₂N and were calculated using the method of Reed and Muench. The VN titers determined at 6 weeks postimmunization indicate no significant differences among the S1, IPV + 2S1, and 2S1 + IPV groups (P > 0.05). However, among the immune vaccine groups, the VN titers were significantly higher in the IPV group than in the other groups (IP, S1, IPV + 2S1, and 2S1 + IPV) (**, P < 0.01).