015 - The duration of immune bodies in the blood after antityphoid inoculation

An important question in the effectiveness of vaccines is how long immunity from them lasts. Depending on the stimulus, the immune system may remember and recognize a pathogen pretty much forever after it is exposed once, but sometimes immunity wanes or even disappears completely, such that an individual can be reinfected with the same pathogen.

The following study is on the antityphoid fever vaccine of the day, how long antibodies from it last after a person is vaccinated. A.E. Wright had previously reported observing people retain some immunity even after two years, and another had claimed to see some immunity after four or even six years in some people.

So the author in this study set out to do a more systematic study, using 24 subjects. Antibodies were measured a) by agglutination, that is, the ability to make bacteria clump together by binding to them, and b) by bactericidal activity.

The results were not great: antibody levels were highest one month after inoculation, but fell off such that after a year, about 80% of the subjects showed no more antibody activity of either type. So the author recommended yearly re-immunization for those at risk for typhoid. Useful if one is in a high-risk area, but not something to give to the general public in a generally typhoid-free area. Good to know though.

Citation: Wollstein, M. The duration of immune bodies in the blood after antityphoid inoculation. J Exp Med 16, 315–324 (1912).