The seropositivity rate of SARS-COV-2 antibody is very high. There is a greater chance of infectivity and death. The S mutation sites of Gamma variants are(49, 50): L18F, T20N, P26S, D138Y, R190S, K417T, E484K, N501Y, D614G, H655Y, T1027I, V1176F. Table shows that D138Y is in the MHC_I_2 A, MHC_II_alpha A, MHC_II_beta B, and MHC_I-like_Ag-recog B domains. R190S, H655Y and T1027I are in MHC_I-like_Ag-recog B, E, G domains, respectively. Compared with the B.1.617.2/Delta variant, the MHC-like domain of the S protein of the SARS-COV-2 Gamma variant has two mutation points, H655Y, and T1027I. It shows that Gamma variant S participates in receptor binding H655Y and participates in membrane fusion T1027I in the MHC-LIKE region. Therefore, the infection rate and mortality of Gamma variants are high. However, the Gamma variant does not have a mutation site located in the MHCassoc_trimer domain. It may not enhance the immune escape of the regulatory region of the S trimer. Therefore, the MHCassoc_trimer domain (144-162) is an important reason why the Delta variant spreads infection faster than the Gamma variant. SARS-COV-2 Alpha variant. B.1.1.7 /Alpha variant has a more tremendous increase in the transmission rate than the earlier SARS-COV-2 virus. However, there is no significant difference in overall mortality. The mutation site of S in the B.1.1.7/Alpha variant is(51): ∆69-70, ∆144, ∆145, N501Y, A570D, D614G, P681H, T716I, S982A, D1118H. Table shows that ∆69-70 is at MHC_II_beta A and MHC_I-like_Ag-recog A domains. shows that D80A is in the MHC_II_beta A domains. Most of the other mutation sites are not in the MHC-like domains. It shows that most of the mutation sites do not affect the MHC-like domain.