The biallelic and monoallelic in-frame variants of IFNAR1 are mostly associated with COVID-19 (W73C, C79R, C79Y, M155I, A264T, S422R, and P335del) and encephalitis (Y215C and N44del), whereas AR loss-of-expression IFNAR1 genotypes (N29fs, V225fs, W261X, E386X, T389fs, and Y481insIHCGICFPV*) also increase susceptibility to LAV vaccines in children, particularly for the MMR and YFV vaccines. This evidence concerns the gene IFNAR1 and encephalitis.