Another common mistake is to use the liquid part of a vaccine without first mixing it with the powder. These happen when the needle never enters the skin or enters and passes back out through the skin before injecting. When using a pistol-grip syringe care must be taken to ensure that no air bubble is present inside the syringe. If an air bubble is present not enough vaccine will be injected when the trigger is pulled. Pistol-grip syringes also need to be checked periodically to ensure that the correct dose is actually being administered.
Some vaccines only protect against a specific subtype.
However, many vaccines will either contain antigens of multiple subtypes or cross-protect against them. Pinkeye is a disease that can be caused by multiple subtypes of the bacteria Moraxella bovis. There are more than 20 subtypes of this species of bacteria. Several pinkeye vaccines contain multiple subtypes but none of them protects against all of the subtypes. When the subtype of Moraxella present on your farm is also present in the pinkeye vaccine you are using, then the vaccine is effective.