Yes, a multi-dose vial can become contaminated. Bacteria can enter during handling or repeated access. Preservatives help limit bacterial growth, but they do not provide complete protection. A sealed cap also cannot establish sterility if the product’s manufacturing quality or packaging integrity is uncertain. CDC
Two reactions from the same vial raise concern, but they do not prove that the batch contained bacteria. Injection-site irritation and inflammation can resemble infection. A clinician needs to assess the affected areas rather than relying on forum experiences.
Do not inject more from the suspected vial. Contact a clinician promptly, and retain its packaging and batch details for review. CDC guidance recommends discarding medication whenever sterility is compromised or questionable. Do not try to make it safe by heating or filtering it yourself. CDC
Painful, hot, swollen skin needs urgent assessment, particularly if redness is spreading or there is discharge. Seek emergency care if you also develop shaking chills, a rapid heartbeat or breathing, faintness, or confusion. These can indicate serious complications. Redness may be less obvious on darker skin. NHS
For prescribed multi-dose medication, use a new sterile needle and syringe every time, follow the storage instructions, and record the first puncture date. CDC guidance generally specifies disposal within 28 days after first puncture, unless the manufacturer provides a different interval, and never beyond the original expiry date. CDC
Previous trouble-free injections do not rule out contamination or an infection now. Getting the current reactions examined is the priority.