Piglets obtain their first protection against Mycoplasma hyopneumoniae from their mother's Colostrum ("passive protection"). The colostrum contains antibodies against a range of infectious agents with which she has already come into contact and which provide some protection for the piglets against these diseases. In a short space of time the antibody level in the blood of the piglets derived from the colostrum decreases, eventually rendering it susceptible to infection.
During the phase of passive protection, the antibodies present may interfere with vaccine administered to the piglet so preventing antibodies being produced by the piglet itself ("active protection").
Many recent studies indicate that the risk of pigs contracting M. hyo infection increases with age. This means that whilst the risk of a piglet being infected while with its mother is very low, the likelihood of infection in the growing and finishing stage is much higher. Three to five weeks of age is therefore the optimal age for M hyo vaccination. Using a reliable vaccine, protection against the consequences of M. hyo can therefore be achieved from the beginning of the period of risk right up to the end of the finishing period. | 
