Which of the following OPV ls are usable?: (A) Only 1, (B) Only 1, 2, (C) Only 1, 2, 3, (D) Only 3, 4
Answer is B. Rules for VVM use in India Rules 1: If the inner square is lighter than the outer circle, the vaccine may be used (Vials 1, 2) Rules 2: If the inner square is the color as, or darker than, the outer circle, the vaccine must not be used (Vials 3, 4).