Dr. James Rowell, Health Officer for San Francisco, U.S A.

"Another marked peculiarity of this epidemic, was the want of prophylaxy afforded by vaccination." And further, "those vaccinated or revaccinated since the commencement of the epidemic, were apparently thereby rendered more susceptible to the disease.—From Dr. Meares' Report of the Small-pox Epidemic, in San Francisco, of 1868-9.