Prefilled syringe with sterility-preserving cap

A medicament container comprising:

• a body having an open mouth defining an axis;
• a pierceable plug engaged over and sealing the mouth;
• a ring engaged around the mouth and over the plug and formed with a hole through which an outer surface of the plug is exposed;
• a cap engageable around the mouth over the ring and plug and including
• an upper cap part,
• a lower ring part fixed around the mouth of the body, and
• a weakened zone joining the lower and upper parts together, whereby the upper part can be easily broken off the lower part at the weakened zone;
• and
• an elastomeric element fixed in the upper cap part and bearing elastically through the hole against the plug outer surface.