Difference between chemoprophylaxis and vaccination

Chemoprophylaxis or chemoprevention is the administration of drugs, such as antibiotics or antimicrobials, to prevent the multiplication of pathogens in healthy individuals. Because administering drugs for preventive purposes involves risks and costs, chemoprophylaxis should be used only in specific and justified cases. Some examples of chemoprophylaxis are preventive treatments with quinine against malaria, with emetine against amebiasis (intestinal infection caused by the parasite Entamoeba histolytica), or more simply treatments with sulfa drugs or antibiotics for prophylaxis of diseases caused by streptococci causing oropharyngeal infections, scarlet fever, or meningococci in cases of meningitis.

Chemoprophylaxis, in addition, can be applied in the surgical setting with preoperative administration of antimicrobials to prevent infectious complications in the postoperative setting. The drugs administered should be active for most infectious microorganisms, and their intake should start 0 to 2 hours before surgery and continue for at least 24 hours.

Subjects who must travel to endemic areas for any reason should also receive chemoprophylaxis one to two weeks before departure, continue throughout their stay, and continue for the four weeks following the last exposure to the pathogen.

Chemoprophylaxis is divided into:

• primary, administration of drugs to people exposed to risk of infection to stop the development of the infectious process;
• secondary,administration of drugs to individuals with an infectious process already in place, but not yet clinically evident, i.e., showing no symptoms (asymptomatic).

What is the Vaccine

Vaccine is a biological preparation that aims to stimulate the immune system, with the production of antibodies, to prevent infectious diseases.  It is based on the administration of small amounts of bacteria or viruses modified and inactivated in the laboratory so that they do not cause the disease, but stimulate the immunological response. Vaccination, or immunoprophylaxis, in fact, reproduces contact with viruses and activates immunological memory so that our body recognizes the infectious agent each time it comes in contact with it and responds by producing antibodies. Some vaccines require booster shots, that is, subsequent administrations repeated several times at a distance in time. Although vaccination has a preventive action, that is, it is given before exposure to pathogens, in some cases, it can also be given after exposure, post-exposure prophylaxis. Rabies vaccination is an example of this because it is administered after the bite of animals with this disease.

Vaccines, in general, consist of:

• live attenuated microorganisms are produced with infectious agents rendered harmless by certain procedures in the laboratory, examples are vaccines effective against measles, rubella, mumps and chickenpox;
• inactivated microorganisms,prepared from viruses or bacteria killed by chemicals or heat exposure, such as those for hepatitis A, polio, and influenza;
• purified antigen vaccines, which contain only certain fragments (antigens) of the pathogen or bacterium e.g., those for anti-meningococcal disease;
• toxid vaccines, use the toxins produced by the pathogens properly purified in the laboratory and inoculated, an example are those for tetanus and diphtheria;
• recombinant protein vaccines,produced with recombinant DNA technology that uses pathogen (antigen) proteins to stimulate the immune system. The antigens are produced in the laboratory using genetic engineering techniques, and are then purified and inoculated, e.g., hepatitis B vaccines.
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Difference between chemoprevention and vaccines

In conclusion, chemoprophylaxis is the preventive action, for possible infections, carried out by administering drugs to healthy individuals, but at risk of infection (primary chemoprophylaxis) or to already infected people who have not yet developed the disease (secondary chemoprophylaxis).

The vaccine, on the other hand, is a prophylaxis based on the immune response that is activated and produces antibodies and immunological memory cells following the administration of antigens to combat infectious agents.

The immune memory remembers the encounter with a specific bacterium or virus even for many years and, in some cases, for a lifetime, protecting the person from reinfection.

Sources: ISS(Istituto Superiore di Sanità), AIFA (Agenzia Italiana del Farmaco)