Against which long-term immunity is not developed.

Long-term immunity may not be developed against some diseases. First of all, the flu. We cannot get the flu once and develop immunity. The same goes for the flu vaccine. It doesn’t work for a long time. But the flu is not the only disease to which long-term immunity is not developed. The cholera vaccine works for 3 to 6 months. Therefore, it is carried out before traveling to regions of the world where the risk of contracting cholera is very high. But after a while, it is necessary to re-vaccinate.