The phrase "petrovac injection c'est quoi" translates from French to English as "Petrovac injection, what is it?" Petrovac is a small coastal town in Montenegro and unrelated to a medical injection. The likely intended word is "Petrovac" used in a medical context, possibly referring to a product or injection called "Tetvac" or "Tetravac." Tetvac or Tetravac injection is a vaccine containing tetanus toxoid and other components such as diphtheria, pertussis (whooping cough), and poliovirus antigens. This injection is a preventive vaccine used to protect against tetanus and other diseases. It is not a treatment but a vaccine to trigger the immune system to produce protective antibodies. Side effects can include mild discomfort, redness at the injection site, or low fever. In French, "injection, c'est quoi?" means "injection, what is it?" An injection is the administration of medication or vaccine via a needle directly into the body, such as intramuscular or subcutaneous injection. In summary:

• Petrovac is a place, not an injection.
• The similar-sounding "Tetvac" or "Tetravac" is a vaccine injection protecting against tetanus and other diseases.
• An injection is a method of delivering medication or vaccines by needle, commonly used in medical treatment and prevention.

Thus, "Petrovac injection c'est quoi?" likely refers to understanding what an injection related to tetanus or similar vaccines is. The injection helps prevent infectious diseases by stimulating immunity.