Post exposure prophylaxis refers to preventive medical treatment started immediately after exposure to a pathogen to prevent infection. Common examples include rabies and tetanus vaccines and immunoglobulins after animal bites, and antiretroviral drugs within 72 hours of HIV exposure. Prophylactic immunization aims to establish immunity before exposure through passive transfer of antibodies or active immunization using killed, attenuated, or recombinant vaccines to stimulate antibody production and prevent disease. Active immunization is often the most effective protection against infectious diseases.

1. Post exposure prophylaxis
Aman Ullah
B.Sc. Med. Lab. Technology
M. Phil. Microbiology
Certificate in Health Professional Education
Lecturer, Department of Medical Lab. Technology
Institute of Paramedical Sciences, Khyber Medical
University, Peshawar, Pakistan

2. Definition
• Post-exposure prophylaxis or Post-exposure
prevention(PEP) is any preventive
medical treatment started immediately after
exposure to a pathogen (such as a disease-
causing virus), in order to prevent infection by
the pathogen and the development of disease

3. Common post exposure prophylaxis
Rabies
• PEP is commonly and very effectively used to
prevent the outbreak of rabies after a bite by a
rabid animal
• The treatment consists of repeated injections of
rabies vaccine and immunoglobulin
Tetanus
• Tetanus post-exposure consists of 2 to 3
injections of tetanus vaccine and tetanus
immunoglobulin

4. Common post exposure prophylaxis
HIV
• In the case of HIV exposure, post-exposure prophylaxis is a
course of antiretroviral drugs which reduces the risk of
seroconversion after events with high risk of exposure to
HIV (e.g., unprotected anal or vaginal sex, needlestick
injuries, or sharing needles)
• The CDC recommends PEP for any HIV negative person who
has recently been exposed to HIV for any reason
• To be most effective, treatment should begin within an
hour of exposure
• After 72 hours post-exposure PEP is much less effective,
and may not be effective at all
• Prophylactic treatment for HIV typically lasts four weeks

5. Common post exposure prophylaxis
Hepatitis B
• If the person exposed is an HBsAg positive source
(a known responder to HBV vaccine) then if
exposed to hepatitis B a booster dose should be
given
• If they are in the process of being vaccinated or
are a non-responder they need to have hepatitis
B immune globulin (HBIG) and the vaccine
Hepatitis C
• Neither immunoglobulin nor antiviral agents are
recommended for HCV post-exposure prophylaxis

6. Prophylactic immunization

7. Prophylactic immunization
• Prophylactic immunization refers to the artificial
establishment of specific immunity, a technique that has
significantly reduced suffering and death from a variety of
infectious diseases
• There are two types of prophylactic immunization:
1. Passive immunization, in which protection is conferred by
introducing preformed antibodies or lymphocytes from
another individual whose immune system was stimulated
by the appropriate antigen
2. Active immunization, in which protection results from the
administration of a vaccine, with dead or harmless living
forms of an organism or with an inactivated toxin, that
stimulates the immune system to produce lymphocytes
and antibodies against that organism or toxin

8. Passive Immunization
• It is sometimes the case that an infectious organism or a poisonous
substance can have such a rapid deleterious effect that the victim does
not have time to develop an immune response spontaneously
• At such times passive immunization with preformed antibodies can
provide life-saving assistance in combating the pathogen or poison
• This situation may arise in victims of poisonous snakebites or botulism, as
well as in those in whom such infections as diphtheria, tetanus, or gas
gangrene have progressed to the point at which bacterial toxins have been
absorbed into the bloodstream
• It is also the case with bites from a rabid animal, although active
immunization is begun at the same time, since the spread of the rabies
infection to the central nervous system is relatively slow

9. Active immunization
• Active immunization aims to ensure that a
sufficient supply of antibodies or T and B cells
that react against a potential infectious agent or
toxin are present in the body before infection
occurs or the toxin is encountered
• Once it has been primed, the immune system
either can prevent the pathogen from
establishing itself or can rapidly mobilize the
various protective mechanisms described above
to abort the infection or toxin in its earliest stages

10. Active immunization
• The vaccines used to provide active
immunization need not contain living
microbes
• What matters is that they include the antigens
important in evoking a protective response
and that those antigens be administered in a
harmless form sufficient in amount and
persistence to produce an immune response
similar to the natural infection

11. ACTIVE IMMUNIZATION
• Bacterial toxins, such as those that cause tetanus or
diphtheria, can be rendered harmless by treatment
with formaldehyde without affecting their ability to act
as immunogens
• These modified toxins, or toxoids, elicit effective, long-
lasting immunity against bacterial toxins
• When immunization against several antigenic
determinants is desired or the important antigenic
component is not known, it may be prudent to use the
entire microbe, which has been killed in a manner that
does not alter it significantly
• Such so-called “killed” vaccines are used to immunize
against typhoid, pertussis (whooping cough), plague,
and influenza

12. Active immunization
• In other cases, researchers have developed attenuated (i.e.,
weakened) strains of bacteria or viruses
• Attenuated vaccines cause an infection but do not produce
the full array of signs and symptoms of the disease,
because the infectious agent multiplies to only a limited
extent in the body and never reverts to the virulent form
• The use of such live microbes provides the most effective
prophylaxis of all, since they truly imitate a mild form of the
natural infection
• The vaccines for yellow fever, poliomyelitis (oral vaccine),
measles, rubella, and tuberculosis
• Although sufficiently attenuated as far as healthy persons
are concerned, live vaccines may cause the full disease in
persons who have an immune deficiency

13. Active immunization
• Recombinant DNA technology has allowed researchers to
use modified bacteria and viruses that are not harmful to
humans to immunize individuals against an antigen from a
pathogenic microorganism
• This approach involves introducing into the DNA of the
harmless microorganism a gene from a pathogenic
organism that encodes an antigen capable of eliciting a
protective immune response but not the full-blown disease
• Once inoculated into the host, the microorganism
generates the protective antigen of the pathogen and
immunizes the host
• An effective oral vaccine against cholera was developed
based on this approach

14. Active immunization
• Active immunization is often the most
effective and least costly method of protecting
against an infectious disease
• Vaccination campaigns against many diseases,
such as diphtheria, polio, and measles, have
been tremendously successful

15. Questions/Suggestions
khurramthalwi@hotamail.com