THE NEW VACCINATION
By HARLEY WILLIAMS
THE announcement this week that the Ministry of Health has sanctioned the experimental use of the new anti-tuberculosis vaccine known as B.C.G. is an event of very considerable importance. Protection against tuberculosis is something long and urgently desired ; to a limited degree it has now been achieved, thanks to the discovery of vaccination with B.C.G. This method is at least thirty years old. It is, beyond doubt, effective. It is safe. Yet only now is it to be used on any large scale in this country. The reasons for this apparent time-lag are part of the general mystery of tuberculosis.
It is nearly half a century since two French scientists, Albert Calmette and Camille Guerin, discovered purely by accident, and began to grow in their laboratory a special strain or family of the tubercle bacillus. That tough and tenacious organism is the cause of tuberculosis, and its deadly characteristics were even in tow well understood. But the new family of microbes which these two French workers isolated for the first time turned out to possess some very different biological qualities. True, it looked like the orthodox tubercle bacillus which caused the deaths of millions ; yet when injected into an animal it produced no serious effects. It was living, but it was harmless. After an enormous number of sub-cultivations over many years Calmette and Guerin became satisfied that their new strain of the tubercle bacillus was, so to speak, permanently tamed. Its behaviour had become fixed. It could not revert to its primitive power of causing disease. To use a rough, but not inaccurate, comparison, it was the relationship between the'jungle lion and the domestic cat. After many generations of growth, this new family of microbes had grown quite harmless like the cat. They named it Bacillus Calmette-Guerin, or B.C.G., and its numerous and beneficent progeny is growing upon slices of suitably prepared potato in laboratories all over the world.
As soon as the harmlessness of B.C.G. became established, Cal- mette hoped that it might be used to fortify human beings against tuberculosis in the same way as vaccination with cowpox arms the body against the more serious risk of smallpox. The theory of vaccination of course is to give a dose of a mild infection in order to stimulate the body to manufacture protective substances against a more serious infection. Edward Jenner first exploited the idea a hundred and fifty years ago, and the word vaccination was originally used to describe this employment for preventive purposes of a disease peculiar to the cow. But the meaning has been extended to cover any method of protection using artificial means to induce the body to manufacture its own anti-bodies. Besides smallpox the idea has been used successfully in diphtheria and typhoid. Calmette attempted vaccination against tuberculosis with B.C.G., and his attempt has succeeded. He proved that B.C.G. confers on the human system an artificially acquired resistance to tuberculosis. It is not certain how long this protection can last, but at least its duration is sufficient to be very beneficial to those who are liable to the disease.
For more than a quarter of a century B.C.G. has been used in France, in South America, and upon a great scale in Scandinavia. The injection is simple, the protective effect takes place without disturbance and we can determine when it has been established. It is in Scandinavia that the active centre of B.C.G. development has taken place in the last ten or fifteen years. From Copenhagen supplies of the vaccine will come for use in this country. Physicians of the highest standing in Norway, Denmark and Sweden regard this method like missioners, and in various parts of Eastern Europe and in India the World Health Organisation is sponsoring the use of B.C.G. Thus the safety of the • method is established beyond reasonable doubt. In Britain and the United States the Health Authorities have been more cautious in sponsoring it, and it has been difficult, at least since 1939, for a medical practitioner in this country to get supplies of the vaccine. But now an official distribu- tion of B.C.G. is to begin, and it will be available for extended use among specially exposed classes of the community.
For the present, and for certain definite reasons, B.C.G. is not to
be generally administered. For this limitation there is sound justifi- cation. In a large number of healthy people mild infections with the tubercle bacillus have already taken place. In modern cities the disease is so widespread that it is easy for the individual to be mildly infected without any knowledge of the fact or any ill effects, and the majority of adults in Britain have received in this way some natural protection against tuberculosis. This protection varies in degree and intensity. Isolated hill-dwellers may never encounter the infection ; crowded urban conditions on the other hand arc very favourable to it. It would be very desirable if we could in some way relate danger and defence, and see that the individual received just enough infection to give him protection, but not enough to give him the disease. For the present that is impracticable, at least by natural means. The trouble is that we can never be quite sure how and when this automatic protection is to develop in any person's life. Provided the infection occurs gradually and in small amounts, the body will be able to handle it with case and safety. It is the violent assault, the overwhelming Blitzkrieg, that is the cause of disaster. To prevent this, B.C.G. will help us.
Now there are certain family and occupational situations which greatly increase the risk of this degree of overwhelming infection with the organism of tuberculosis, and it is in them that B.C.G. finds its unique opening. Take the medical student, for instance. At a susceptible age, he is liable to come in contact with tuberculous infection from hospital patients to a very much greater degree than he has ever done in his home or at school. The same with hospital nurses. The greatest risk of all is to a child or adolescent in a house- hold where there is a case of active tuberculosis. In such situations B.C.G. will give artificial protection just for the period when it is most needed. Where the infection has previously taken place, B.C.G. will not be needed, and fortunately we have a simple test which can be used to select those who require vaccination and leave those for whom environment has already taken the matter in hand.
B.C.G. vaccination is thus a method of choice for a particular situation, and not a preventive measure which shottld be used for everyone. It would be quite impracticable to employ it in this highly urbanised country on any general scale. Some day in the future it may be possible to set up a universal system of anti- tuberculosis vaccination ; but for us that day is not yet. The control of tuberculosis will still depend very largely upon general measures of hygiene, upon satisfactory nutrition, and what is generally under- stood by the term "a good standard of living."
Yet B.C.G. is a very great advance. It may inaugurate something like a revolution in our method of handling a disease which still kills seventy or eighty of our people every day in the year. Tubercu- losis is the greatest challenge to preventive hygiene, and we cannot afford to overlook any means that will help us to control it, even though, like B.C.G., it is a specific method of particular value, and not a preventive agent of general application.
Albert Calmette is dead, but I imagine that the man who repre- sents the third letter of B.C.G.—the distinguished bacteriologist, Camille Guerin, who, now an old man, still lives and works in his laboratory in Paris, will be proud that, after so many disappoint- ments, his method of vaccination is to be employed in England as it has long been in his own country, Latin Europe and Scandinavia.
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