As lactating cows will also be vaccinated, that cre-ates a real concern of local authorities about the possible threatto public health. The present study investigated, using very sensi-tive and specific techniques, if vaccination of cows during lactationleads to excretion of viable RB51 vaccine strain in milk up to nineweeks post-vaccination, and concluded that the public health haz-ard associated with the consumption of milk from post-partumRB51-vaccinated cows is very low, since RB51 strain was not foundin 233 out of the 234 milk samples (99.6%).