With the present annual average of 200,000 reported cases and 5,200 deaths—a death for every 39 cases reported—whooping cough warrants the concerted attention of clinicians and health officers. Its prevalence depends on the high index of communicability and the profuse dissemination of pertussis bacilli before cardinal clinical symptoms are well established. With quarantine so frequently delayed until the contagious period has nearly passed, new cases are inevitable. As pertussis is fatal only during the first few years of life, preventive inoculations should be undertaken as early as active immunization is likely to result.
Since 1916 Danish investigators have used a pertussis vaccine which contains 10,000,000,000 bacilli per cubic centimeter. Although their total dose of 2.2 cc. failed to prevent the disease, "fewer whooping cough deaths occurred when the inoculations were completed before the disease broke out."1
To increase the dose appreciably without risk and possibly to enhance its potency,