<prompt> A PHC medical officer wants to give pulse polio immunization. The following finding in the Vaccine Vial Monitor VVM indicates that the vaccine should not be used:Inner square is white, outer circle is blueInner square is blue but lighter than outer circleInner square matches the color of the outer circleInner square is lighter than outer circle  <response>: c. Inner square matches the color of the outer circleRef: Nelsons 20e p 1561, Ghai 8e p 190-194Interpretation of the color change of VVM is as follows:Inner square is white, or lighter than outer circle: If the expiry date has not passed, vaccine can be usedInner square matches color of outer circle or is darker than outer circle: Vaccine should be discarded, regardless of the expiry date. 