During a recent smallpox outbreak in Madras, India, 1,100 people who had been in contact with smallpox infection were given oral doses of a new drug methisazone ( N-methylisatin β-thiosemicarbazone).1 Only three cases of smallpox occurred in this group; all three were mild, although two patients had not received a full dosage of the drug. Another group of 1,126 smallpox contacts were vaccinated but did not receive methisazone. Among these, 78 cases of smallpox developed, 12 of them fatal. These results are indeed significant, indicating that a synthetic drug can protect against a virus capable of producing lethal disease. This drug may become an important means of protection against smallpox. Further, it seems likely that chemotherapy may be used successfully in the fight against other viral diseases.
Vaccination alone after contact with a smallpox patient often proves ineffective, especially if done during the period of incubation—even during the first days
ANTIVIRAL CHEMOTHERAPY IN PREVENTION OF SMALLPOX. JAMA. 1964;187(2):145-146. doi:10.1001/jama.1964.03060150069023