Chandrika 14 -20 April 2012. English version of Malayalam article
Of Micro-organisms and Men: Immunity and Vaccines
The best laid schemes of mice and men-
Often go awry
John Steinbeck. 1937
There are billions of micro-organisms in our environment. Some have a symbiotic relationship with us, meaning that the relationship between man and the micro-organism are mutually beneficial. Thus there are bacteria resident in our gut, that eats some of the food we have eaten, but in return they make useful vitamins for us to absorb and use. If we kill these harmless or good bacteria, two consequences follow. The first relates to losing out on the benefits provided by the bacteria like the vitamins produced. The other more dangerous, relates to the replacement bacteria. If we kill the bacteria in our gut with a powerful antibiotic, then other bacteria will replace them and these may be harmful bacteria and they will certainly be antibiotic resistant. This replacement phenomenon occurs sometimes even if we use vaccines to eliminate resident micro-organisms.
Not all micro-organisms are good for man. Some produce disease and death. Some harmless bacteria may themselves become harmful to us when our resistance is lowered. Thus Staphylococcus epidermidis is part of human skin flora but in people with catheters (like patients undergoing dialysis) this can produce lethal disease. It is important to hold this complexity at the back of our minds when we consider vaccines and immunity.
How vaccines work
If a child gets a disease like chicken-pox he will get a little fever and a couple of boils and after a few days he will recover. The reason for his recovery is that the body recognizes this new viral invasion and produces antibodies against the virus. Once produced, the antibodies eliminate the chicken pox virus. And after this the person will never ever get chicken pox, because he is now immune. Not only that, women who have had chicken pox pass on some of these antibodies to their babies and their babies are protected by this immunity got from mothers (called passive immunity) for 3 to 9 months. During this period, if the child comes across infection, they may get a very mild type of infection that goes unnoticed. With this mild infection, the child develops active immunity that lasts a life time.
If we kill the virus and inject its protein into the skin, the dead virus cannot produce infection. However the body may take up the viral protein and make antibodies as if this were a real infection. This is the principle behind vaccines. It has been a major advancement in our battle against disease.
Evaluating Costs and Benefits
Vaccines against deadly diseases like small pox that spread easily in the community are a good idea but there is no meaning in making vaccines against every mild disease. This can do harm in a number of ways.
1. The vaccine may be associated with side effects more harmful than the disease. The Pentavalent vaccine seems to fall in this category but this has been discussed else where in this magazine.
2. The replacement organisms that take the place of the eliminated bacteria or virus may in fact be more lethal than the original organism. An example of this is seen when they used the 7 valent pneumococcal vaccine in the West. The new strains (that replaced the old vaccine strains) were more harmful and more antibiotic resistant.
3. The cost: benefit ratio of the vaccine. This is a crucial factor especially when considering vaccines for minor diseases, because the vaccine has to be given to everyone in the community to prevent a disease which may have affected only one or two persons. The cost of treating the mild disease in these two must be compared to the cost of giving the vaccine to every one in the community. Often investing in other programmes will save many more lives than spending money on vaccine against minor diseases.
Hypersensitivity and the Pentavalent Vaccine
In this context it is pertinent to discuss the Pentavalent vaccine being pushed by vaccine manufacturers and some international organisations. The vaccine is known to have caused deaths in Sri Lanka, Bhutan and Pakistan. No other cause for the deaths were found on investigation, and according to the WHO’s Brighton criteria, this makes vaccine the probable cause of death. Many persons have received the vaccine with no harmful effects. The reactions appear to be a hypersensitivity reaction in some persons. This is why the National Technical Advisory Group on Immunization (NTAAGI) insisted that before it is introduced in the country we must look for side effects and deaths in a limited area.
An example of a drug that causes hypersensitivity reaction and deaths is Penicillin injections. This is why doctors test for sensitivity to penicillin every time before giving it. There is however no test for sensitivity to Pentavalent vaccine and so if Pentavalent vaccine cause hypersensitivity in some – it cannot be used in the national immunization programme because every child is at risk of death from undetected hypersensitivity.
Puliyel is member of the Government of India’s
National Technical Advisory Group on Immunization