Abbreviations
BCG: Bacillus Calmette-Guérin
COVID-19: Coronavirus disease-2019
MMR: mumps-measles-rubeola
NOD: Nucleotide-binding oligomerization domain-containing protein
RT-PCR: reverse transcription polymerase chain reaction
Th: T helper-cell
TLR: Toll-like receptor
TNF-α: Tumor necrosis factor alpha