Immunity is an important topic of Community Medicine.

1. Immunity

2. Immunity
Immunity is the ability of the body
to recognize ,destroy and eliminate
antigenic material
(e.g.bacteria,virus etc.) foreign to
its own .

17. Antigen
An antigen is a substance protein or
polysaccharide in nature which
when introduced into the body is
capable of inducing an immune
response leading to formation of
antibody with which it reacts
specifically .

18. Antibody
Antibodies are immunoglobulin that
react specifically with the antigens
that stimulate their production.
Antibodies are- IgG,IgM,IgD,IgA,IgE.

55. ADVERSE EVENTS
FOLLOWING
IMMUNIZATION
Vaccines used in national immunization
programmes are extremely safe and
effective. However, no immune response is
entirely free from the risk of adverse
reactions or remote sequelae.

56. COMMON, MINOR VACCINE
REACTIONS
 Local reaction
 (pain, swelling, redness)
 Irritability, malaise and
 non-specific symptoms, fever
 gastrointestinal upset
 Keloid (thickened scar tissue) from the BCG lesion
is more common among asian and african
populations.

57. Contraindications to vaccines
Vaccine Contraindications
All An anaphylactic reaction• following a
previous dose of a particular vaccine
is a true contraindication to further
immunization with the antigen
concerned and a subsequent dose
should not be given, OR, Current
serious illness
Live vaccines (MMR,
BCG, ;Yellow fever)
Pregnancy.
Radiation therapy (i.e. total-body
radiation).
Yellow fever Egg allergy.
Immunodeficiency (froll) medication,
disease or symptomatic HIV infection

58. CONTD.
Vaccine Contraindications
BCG Symptomatic HIV infection
Pertussis-containing Anaphylactic reaction to a previous
dose

74. Herd immunity
 Herd immunity (or community immunity) describes a
type of immunity that occurs when the vaccination of a
portion of population (or herd) provides protection to
unprotected individuals.
Herd immunity theory proposes that in diseases passed
from individual to individual, it is difficult to maintain a
chain of infection when large numbers of a population are
immune.
The higher the number of immune individuals, the lower
the likelihood that a susceptible person will come in
contact with an infectious agent .

75. Herd immunity provides an immunological barrier to the
spread of disease in the human herd. For example, when an
infectious disease is introduced into a "virgin" population,
that is, population with a very low or no immunity, the
attack and case fatality rates tend to be very high involving
practically all susceptibles as it had happened in the very
severe measles epidemic in the Faroe islands, in 1854,
where the population had no previous experience of
measles. The epidemic wave declined with a build-up of
herd immunity following natural infection.
Elements which contribute to herd immunity are
(a) occurrence of clinical and subclinical infection in the
herd,
(b) immunization of the herd, and
(c) herd structure.

76. Studies have shown that it is neither possible nor necessary to
achieve 100 per cent herd immunity in a population to halt an epidemic
or control disease. as for example, eradication of smallpox.
Herd immunity may be determined by serological surveys