20 babies got admitted into a hospital in Nigeria with neonatal tetanus. Mothers of six of them have been vaccinated with at least two doses of the vaccine during pregnancy. All mothers and babies, including the unvaccinated ones, had the antibodies at a much higher than the protective level (0.07 IU/ml and above). Mortality rate among unvaccinated was 43%. Mortality rate among vaccinated was 50%.
However, there also exists a study proving that 2-3 vaccines during pregnancy significantly reduce the incidence of neonatal tetanus. On the other hand, vaccination increased mortality from other causes by 18%.
A similar case in Nigeria in 1981. Also a case of lymphoma remission after contracting measles had been documented in 1949 in Cuba.