THPO and infection: Upon infection with blood-stage malaria, however, this level was slightly increased to approximately 49 at early prepatency on day 1 p.i., before it steadily dropped to approximately 27 above normalization level towards the end of the crisis on day 11 p.i. Protective vaccination did not change the constitutive expression levels of Thpo, and it also did not affect the slight, but not significant, malaria-induced increase in expression during the first day of infection.