Which of the following must be avoided when preparing vaccines for administration?

When preparing vaccines for administration, it is crucial to ensure the safety and efficacy of the vaccination process. Reusing syringes without changing the needles is a practice that must be avoided. This is because reusing syringes can increase the risk of infection and contamination, as well as lead to improper dosing and potential adverse reactions. Each vaccine dose must be handled with a new, sterile syringe and needle to maintain aseptic conditions and ensure patient safety.

In contrast, checking expiration dates and using aseptic techniques are essential components of proper vaccine preparation. Expired vaccines may not provide the intended immunological response and could cause harm, while aseptic techniques are vital in preventing contamination of the vaccine and maintaining sterility during administration. Mixing different vaccines in a single syringe is not recommended either, as it can create interactions or inactivate certain vaccines, impacting their effectiveness. Thus, proper vaccine administration protocols are crucial for public health and safety.