Air sampling to recover variola virus in the environment of a smallpox hospital.

The view is widely held that variola is highly infectious, and it was therefore thought of interest to obtain precise information on the amount of virus disseminated in the air by smallpox patients at various stages of their illness. To this end, measured samples of air in and around the smallpox wards of the Infectious Diseases Hospital, Madras, were tested for the presence of variola virus. Surprisingly, virus was recovered on one occasion only by the air sampling device used.

The use of vaccinia hyperimmune gamma-globulin in the prophylaxis of smallpox.

This paper records an attempt to assess the prophylactic value of immune gamma-globulin, prepared from the serum of recently vaccinated adults, in the protection of close contacts of smallpox in Madras. The results serve to confirm findings of a previous study made in Madras in 1953, and show that the incidence of smallpox in close contacts given immune gamma-globulin prophylactically was about a quarter of that in the control contacts who received no such passive immunization-a statistically significant difference. Because of the limited supply of immune gamma-globulin, it is likely that its prophylactic use will be restricted to those especially at risk, for example, close unvaccinated family contacts, newborn infants and pregnant women.

Comparison of dried vaccine with fresh Indian buffalo-calf lymph in revaccination against smallpox.

It was known that the liquid glycerinated buffalo-calf lymph issued for routine use in smallpox vaccination in Madras gave a high take rate in primary vaccination but that successful takes on revaccination amounted to less than 10%. In the course of studies on smallpox carried out in Madras, it was therefore decided to compare a potent freeze-dried English vaccine with the current Madras lymph by revaccinations carried out on persons admitted to the Madras Infectious Diseases Hospital for ailments other than smallpox. The take rate of the freeze-dried preparation in these tests was 63% as against 27% for the liquid preparation.

Studies on the virus content of mouth washings in the acute phase of smallpox.

Epidemiological observations suggest that smallpox is not highly infectious in the febrile pre-eruptive period of illness. As virus is first discharged by most patients from lesions in the mouth or upper respiratory passages, mouth washings or garglings from smallpox patients in the acute stage of the disease were examined for virus. Only five specimens were obtained in the first two days of illness but no virus was recovered from them.

Studies of smallpox antibody levels of sera from samples of the vaccinated adult population of Madras.

In view of the endemicity of smallpox in Madras and the poor take rate on revaccination with the lymph in current use, it was felt that the immunity of the general adult population might be relatively low. In an attempt to obtain some measure of this, sera were obtained from over 300 adults in Madras for the estimation of serum antibody. The results of neutralization tests against variola virus made on these sera showed that about 10% of those who had good scars from infant vaccination showed little or no antibody.

Laboratory and vaccination studies with dried smallpox vaccines.

In a vaccination and laboratory study, two dried smallpox vaccines (designated P and Q) were tested at intervals of 4, 8, 16, and 32 weeks after storage at both 37 degrees C and 45 degrees C. Vaccine P was also tested after 64 weeks at these temperatures and gave 100% successful vaccination rates after all periods of storage at both temperatures. Vaccine Q deteriorated within four weeks, rapidly at 45 degrees C and less rapidly, but very substantially, at 37 degrees C.