009 - Remarks on the Results which have been Obtained by the Antityphoid Inoculations and on the Methods which have been Employed in the Preparation of the Vaccine

This is another article about the typhoid fever vaccine, more reliable than the previous (008) in my opinion.

Most of the article is a detailed description of how the vaccine may be prepared and tested, which is interesting in itself somewhat; apparently it was made of somewhat-attenuated (that is, less capable of causing severe disease) Salmonella bacteria (the pathogen that causes typhoid fever), grown in culture and then killed by heating or chemical lysis.

It had to be tested for toxicity using guinea pigs—as noted in 008, it was fairly nasty stuff, probably due to all the endotoxin (a component of some bacterial outer membranes that causes immune overreaction and the resulting problems)—and then this toxicity, along with turbidity of the vaccine material, determined the dose to be given to people.

Near the beginning of the article, there are some interesting statistics. A number of British troops in India received vaccination of portions of their soldiers, and the number of cases of typhoid was observed for each. Most of the troops had at least 100 people in each group, usually many more in the unvaccinated group, so it had the potential for a decent comparison. In almost all comparisons, fewer vaccinated than unvaccinated soldiers came down with typhoid, and fewer died from it. The cases that did occur in vaccinated tended to be reported as mild.

Overall, the comparison may not be that impressive (vaccinated: 95 out of each 10000 got sick, 20 in 10000 died; compared to unvaccinated: 250 in 10000 got sick, 34 in 10000 died). But the authors point out that those that received the vaccine tended to be men who were more likely to be susceptible to typhoid in the first place: they were young and had only recently arrived in India, whereas those who were unvaccinated tended to be older and had been exposed to typhoid before, so might have developed natural immunity. In light of that, the numbers seem more impressive. But still, it was an unblinded study with uncertain diagnostic criteria, I think. Consistent with other studies of its kind, though.

Citation: Wright, A. E. & Leishman, W. B. Remarks on the Results which have been Obtained by the Antityphoid Inoculations and on the Methods which have been Employed in the Preparation of the Vaccine.Br Med J 1, 122–129 (1900).