Immunisation used for offensive and defensive purposes during the Second World War

The best defence against natural or intentional biological agents during armed conflict is usually immunisation, as with typhoid fever, but exceptional circumstances are informative. A large iatrogenic epidemic of hepatitis B occurred in 1942 due to contaminated lots of yellow fever (YF) vaccine used in the US military, even though there was no natural risk of infection. YF vaccine was intended to protect against Japanese Army's use of YF as a biowarfare agent, which did not eventuate. Salmonella typhi was used to infect German soldiers in a Paris cafe during Christmas 1941 in the knowledge that the cafe staff but not the soldiers were likely to be immunised against typhoid fever. German Army use of the Weil-Felix reaction to eliminate civilians likely to be typhus infected was subverted by Polish medical officers. They immunised civilians with locally produced Proteus antigens to create false-positive Weil-Felix reactions in order to exempt men from forced labour schemes. Immunisation against biowarfare agents has a mixed record, indicating that vaccines rarely cover well for intelligence gaps.

Automated summary

Immunisation is the best defence against biological agents in armed conflict, but there have been exceptions where vaccines were ineffective or even caused epidemics. The use of contaminated yellow fever vaccine led to a hepatitis B epidemic in the US military in 1942. German soldiers were deliberately infected with typhoid in 1941, targeting those who were unlikely to be immunised. Immunisation against biowarfare agents has had mixed results, highlighting the limitations of vaccines in addressing intelligence gaps.