Herd Immunity And Cold Chain – This book covers the entire syllabus of “Community Health Nursing” prescribed by the Universities of Bangladesh- for Basic and diploma nursing students. We tried to accommodate latest information and topics.
This book is examination friendly setup according to the teachers’ lectures and examination’s questions. At the end of the book previous university questions are given. We hope in touch with the book students’ knowledge will be upgraded and flourished. The unique way of presentation may make your reading of the book a pleasurable experience.
Herd Immunity And Cold Chain
Herd immunity:
It mean a level of immunity of a group of people or a community to a particular disease. It implies group protection beyond that afforded by the protection of immunized individuals or in other ward one gets the benefit of an immunization programme without being immunized by
belonging to a group who were immunized.
Examples:
- If 80 to 90% population of a community have been immunized against a particular disease, rest of the population (10-20%) enjoy the immunization without being immunized.
Herd immunity production/ Elements contribute to herd immunity:
- Occurrence of infection in the Herd :
Clinical infection Sub clinical infection.
- Immunization of herd:
- Herd structure: It includes.
✓ Host population of the same species.
✓ Presence with distribution of animal host.
✓Insects’ vectors.
✓Environmental and social factors that be favour or inhibit the spread of infection from host to host.
Merits or importance:
a) If 80 to 90% population of a community have been immunized against a particular disease, rest of the population (10-20%) enjoy the immunization without being immunized.
b) Herd immunity provides an immunological barrier to the spread of disease [the ongoing EPI. programme is keeping up the herd immunity at a very high level]
c) If the herd immunity is sufficiently high, the occurrence of an epidemic is highly Unlikely.
d ) Some disease can be eradicated by herd immunity e.g. diphtheria, poliomyelitis.
e) Herd immunity does not protect the individuals in case of tetanus
Influencing factors of herd structure:
➤ Population mobility
➤ New births,
➤ Deaths.
Milestones in vaccination:
- Small pox vaccine 1798
- Rabies vaccine 1885
- Cholera vaccine 1892
- Toxin/antitoxin immunization against diphtheria. 1913.
- BCG-1923
- Pertussis-1923
- DT-1923
- TT-1927
- Influenza vaccine -1937
- Yellow fever -1937 (17D) Salk’s Polio vaccine -1954
- Sabin live OPV-1957
- Measles vaccine – 1960
- Rubella vaccine – 1962
- Hepatitis-B vaccine-1975
Cold chain system
The cold chain is a system of storage & transport of vaccine at optimum temperature from the manufacturer to the actual vaccination site.
The system is as follows:
Procurement of vaccine by the air
↓
Airport
↓
By vehicle
↓
EPI headquarter cold room
↓
By vehicle (in cold boxes)
↓
District ILR & deep freeze
↓
By vehicle (in cold box)
↓
Thana & ILR refrigerator (1 month)
↓
Vaccine carrier
↓
Field level (8 hours storage)
↓
Ice vaccine pack
↓
Use of vaccine.
Cold chain equipment:
■ Walk in cold chain room (WIC):
- Located at regional level.
- Store vaccine up to 3 months.
- Serve 4-5 districts.
■ Deep freezers & ice lined refrigerators (ILR’S) To make ice parks
- To store opv and measles vaccine
- District & WIC location
■ Small deep freezers & ILR
- PHCs
- Urban FPC
- Post-partum center
a) To prepare frozen ice packs with are used in cold boxes with vaccine carriers.
■ Cold boxes: Keep vaccine cold up to 1 week
■ Vaccine carriers: Keep vaccine safe up to 3 days
■ Day carriers safe few hours.
■ Ice packs
Importance of cold chain
- To maintain potency of vaccine.
- For the storage of vaccine.
- For the transportation of vaccine at low temperature
Risk of cold chain failure
- Is greater in sub center& village level.
- For this reason vaccine is not stored at the subcenter level & must be supplied in the dayof use.
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