What is an important step when preparing vials for injection?

Wiping the vial stopper with an alcohol swab is crucial in the preparation of vials for injection. This step helps to reduce the risk of contamination by disinfecting the rubber stopper, which is the point where the needle enters the vial. Since the stopper can harbor bacteria or other pathogens from handling, ensuring that it is cleaned with an alcohol swab before accessing the vial minimizes the chance of introducing contaminants into the solution during the injection process.

Other options presented do not align with standard protocols for injection preparation. Exposing vials to light can potentially degrade certain medications, heating the solution may alter its properties and efficacy, and using repeated needle access without proper cleaning can increase the risk of contamination. Therefore, wiping the vial stopper is the most essential step in ensuring sterility and safety when preparing for injections.