Herd immunity is achieved when a large percentage of a population is immune to an infectious disease, providing indirect protection to those who are not immune. It works by reducing opportunities for disease transmission, eventually eliminating the disease from the community. Herd immunity can be achieved through vaccination or natural infection and depends on factors like the human population size and density, presence of animal reservoirs or insect vectors, social interactions, and access to healthcare and nutrition.

1. Presented By:
Dr.Md.Salequr Rahman
Dep. of Community Medicine

3.  Oxford Text book of public health
“ It is the relative protection of a
population group achieved by reducing or
breaking the chains of transmission of an
infectious agent because most of the population is
resistant to infection through immunization or
prior natural infection”

5. HERD STRUCTURE: (IT INCLUDES-)
 Human population
 Animal reservoir or host
 Insect vector
 Environmental factors
 Social factors

6. CONCEPTS BEHIND HERD IMMUNITY

14. MACHANISOM:
Immunization of 70-80% people
Remainder 20-30% are either cases or susceptibles
Scanty number of primary cases
Frequency of secondary case development decreases
Eventually secondary case development becomes nil

15. Tansmission block of the disease
No disease

16. HOW HERD IMMUNITY CAN BE ACHIEVED:
 Immunization
 Clinical & sub-clinical infection
 Elimination of insect vector
 Elimination of animal reservoir
 Provision of safe water supply
 Provision of sanitary disposal
of fefuse & sewage
 Provision of proper nutrition

18. FACTORS THAT AFFECT HERD IMMUNITY:
A. Demographic : large number
of births how are not prooerly
immunized
B. Health care facilities
C. Social & political factors
War
Cyclone
Famine
Economic disruption