The article “a” is used before abbreviations

冠詞の”a”について

◎ The article “a” is used before abbreviations that start with a consonant sound. For example,

-> a BAC of 0.2 g/dL
-> a URI recommended vaccination

In the second example, the first letter of the abbreviation URI makes a “you” sound, which is a consonant sound. Therefore, the article “a” is used even though the letter “u” a vowel.