The resistance of the body to the effects of pathogenic organisms is called immunity. It is an important defence mechanism of the body to fight against several diseases.
This immunity in the body is of two types:
(i) Active Immunity:
It develops as a result of the contact of an individual with pathogenic organisms or their products. These stimulate the body to produce antibodies in response to antigens i.e. foreign substances. The immunity may be acquired either through the infection of a pathogen or administration of a vaccine. Active immunity takes a few weeks to a few months to develop, but persists for a long time.
The immunity produced through vaccination is specific for a particular disease. For example, the immunity established against chicken pox or mealsles is not effective against cholera or tuberculosis,
(ii) Passive Immunity:
It is produced when antibodies formed in one human being are transferred to another. It may be acquired through transmission of maternal antibodies to the fetus through the placenta, for example for chicken pox, mealsles, diphtheria, polio tetanus.
Injection of antiserum i.e. blood plasma containing antibodies prepared against a specific disease e.g. tetanus, diphtheria or rabies also develops passive immunity in the body. The transfer of lymphocytes also gives passive cellular immunity against viruses, bacteria, fungi and some protozoa.
This passive immunity is rapidly established but last for a short while. Passive immunization has therefore limited utility as compared to active immunization and is used mainly as a short term preventive measure.
Reduced immunity of the body results in high susceptibility to infection and may lead to a number of disorders or diseases. These immune deficiencies may arise due to some genetic defects in the body.
They may also be acquired as a consequence of malnutrition, metabolic abnormalities, exposure to X-rays, toxic effects of drugs or pathogenic organisms recognizing the potential of immunisation as a low cost efficient technology for child survival and prevention of disability, the government has started the expanded programme on immunisation in 1978 with the objective of reducing the morbidity, mortality and disability due to diphtheria, whooping cough, tetanus and tuberculosis by making free vaccination services available to all eligible children and expectant mothers.
Polio vaccine was included in the programme during 1979-80 and tetanus in 1980- 81. BCG was brought in 1981-82 and mealsles vaccine was initiated in 1985-86. But the Universal Immunisation Programme was launched in 1985 as a part of over all national strategy to bring down infant and material mortality in the country by providing immunization to all infants against six preventable diseases and pregnant women against tetanus.
In 1986 the Universal Immunisation Programme was named as one of the Technology Missions and the following objectives were spelt out:
(i) To cover all pregnant women against tetanus and at least 85% of all infants against six vaccines of preventable diseases by March 1990.
(ii) To increase production, upgrade testing facilities and develop the means, support and distribution of vaccines at the required low temperatures to maintain their potency.
(iii) To achieve self-sufficiency in vaccine production and manufacture of cold chain equipment.
In the pursuance of the World Health Assembly resolution of 1988, in addition to the administration of routine Oral Polio Vaccine through the Universal Immunisation Programme, the Pulse Polio Immunisation Programme was launched in 1995-96 to cover all children below the age of 3 years.
With the implementation of all these immunization programmes the infant mortality for the country as a whole has reduced. It was also estimated that vaccine preventable diseases were responsible for about one-fourth of the total infant deaths. While the plasmodium falciparum which is responsible for spreading more lethal form of malaria showed an upward trend during 1970s and thereafter.
The multidrug resistant strain of the disease also threatens to pose serious problems due to inadequate coverage of the programme and back of coordination between public and private health care systems. Now it is proposed to intensify the efforts for the full containment of the disease.
Accordingly, major focus is being given to insecticidal spraying for vector control in areas having more than 2/1000 cases reported. In the remaining areas, focal spraying and effective case surveillance is being taken up. These efforts are being developed with training of workers and encouraging community participation, along with decentralization of drug distribution and fever treatment etc.
The areas identified as more unalterable to malaria are largely tribal, difficult, and remote and forested inaccessible areas. The high transmission areas are the North Eastern States and tribal areas of Andhra Pradesh, Chhattisgarh, Jharkhand, and Madhya Pradesh. In 1977 the modified plan of operation was launched with the immediate objectives to prevent deaths and reduce morbidity due to malaria. This programme was integrated with primary health care delivery system.