Notes on a series of investigations into the methods of immunisation against diphtheria

Having in view the difficulties which arise in diphtheria immunisation, this thesis will attempt to show: - (1) a comparison between different immunising agents, especially in connection with results and reactions. (2) a consideration of questions of immunity, etc. which may arise in this investigation. (3) Any special feature of interest. Many have been noted. In most cases this will be remarked upon. (4) Any conclusions which may be drawn from this work, as to the most convenient practical means of carrying out diphtheria immunisation. The word 'practical' is of some importance, as this thesis is not intended to deal with more than this aspect of the work. The Schick Test is taken as a reliable index of immunity. There are many references in the literature to Diptheria in 'S -' individuals. Moloney and Fraser report cases which were 'S -' with less than 1/50 A.T. units per cc. of blood, but clinical workers are agreed that for their purpose it is a satisfactory test. Joe describes it as a 'satisfactory guide'. Parrish and O'Kell agree that the 'S -' state is more or less permanent. Harries22 in 1930 asserts that "no 'S -' person has ever had clinical diphtheria ". Bousfield in presenting the case for Schick testing as a routine measure describes a 'S -' state as a "training in antitoxin production ", the real basis of active immunisation. Rhoads is of the opinion that impotent toxin and bad technique is the cause of 'S -' reaction in susceptible individuals. The work of McLeod, and others, in Leeds helps to explain the discrepancies in the test, by their differentiation of the 'mitis' and 'gravis' type of organism. Parrish and Wright in 1935 report several small epidemics of diphtheria in 'S-7 individuals. The epidemics occurred in a residential school, an orthopaedic children's hospital, and a general hospital. They noted that the cases were all due to the 'gravis' type of organism. Those occurring in 'S -'s were all mild cases clinically and recovered completely without complications. (These cases were both immunised and natural 'S-'s.) In the Orthopaedic Hospital mentioned, the carrier rate for 'gravis' organ isms was 40% -- the patients here were immunised as a routine. Dudley, May and O'Flynn describe an epidemic due to the 'gravis' organism in the Greenwich Hospital School. The cases were mild and often 'unrecognisable clinically'. The school consists of 900 boys and it kept at a 90% 'S-' level. They are of the opinion that immunisation prevented an outbreak of severe diphtheria, such as has recently occurred in the North of England. It need only be said that a test which indicates that a person will only suffer from a mild disease instead of a severe one, with a high mortality rate, is of great value. One seems justified, therefore, in relying on skin tests in judging the efficacy of an immunising agent or method. In the actual employment of immunisation in a Public Health Department, toxin titration of the blood is not practicable