When a disease causing micro–organism enters the body, the immune system is stimulated to fight the invader. The fighter cells produce antibodies to neutralize the invasion. If the individual’s immune mechanism is compromised by poor nutrition or environmental hygiene, or drug abuse, the body takes a longer time to marshal its response.
Vaccines are injections that contain small amounts of bacteria or virus, with the harmful elements removed. Bacteria causes diseases such as diphtheria, pertussis and tetanus, while viruses lead to polio, hepatitis, rubella, measles, mumps, chicken pox and rabies. When vaccines are injected, they artificially stimulate the body to produce antibodies. Consequently, when the real invader enters, the system is already geared to recognize the enemy and antibodies are promptly released to do battle.
The organism is killed or kept alive depending on the specific vaccine requirement. For instance, vaccines like oral polio, rubella, measles and mumps utilize the live but weakened (attenuated) virus. The rabies and the Salk polio vaccine utilize the ‘Killed’ virus which undergoes treatment with heat and drugs. Although dead, the parasite still stimulates an antibody response.
The tetanus vaccine utilizes the toxin excreted from the bacteria. The hepatitis B vaccine uses a new technology called ‘Recombinant DNA technology’. Here, the genetic information of the virus that causes this disease is isolated. This reveals the mechanism by which the hepatitis B surface antigen is manufactured. When injected into someone, it produces antibodies that fight the virus.
Meanwhile, the animal or human cells, used to ‘Culture’ the parasite are generally derived from three sources. They could be ‘Human diploid cells’ derived, for instance, from the lung of a human fetus. Or they could be ‘ Vero cells’ from the kidneys of the African green monkey, or primary chick embryosis cells. Once obtained from the original host, a ‘Cell line’ is developed and maintained in the laboratory and there is no need to go back to the original host.
The only exception, however, is in the case of the live (oral) polio vaccine. Every bulk batch of the polio vaccine requires a return to the monkey host for obtaining fresh cells. A vaccine has a shelf life of up to three years, provided it is consistently maintained at a stable refrigeration temperature of 2 to 8 degrees Centigrade.
The main concerns about the vaccine manufacturing process focus on the instability of the micro–organism, impurity in the ‘Cell line’ and the toxicity of the purification and stabilizing agents. The latter include chemicals and heavy metals like mercury. The live polio vaccine, for instance, is highly sensitive to unstable temperature and is exposed to contamination if the vial is opened and left unutilized for several hours by health workers.
Several Western scientists have expressed concern about the use of primate tissue in vaccine manufacturing, and have urged that a “Serious effort” be made to stop its use. Last year, Western newspapers had reported the possibility of an experimental oral polio vaccine used in Africa in the 1950s being contaminated with the HIV virus present in the monkey cells used in the manufacturing process. This they said, could have led to the virus jumping species and finding a new host in humans.