Where does mastitis vaccination fit in modern herd health programmes?

Mastitis vaccination increasingly supplements established udder health programmes, but its value depends on the pathogen, the outcome being measured and the herd context. This article explains the immunological rationale for vaccination and translates evidence on Escherichia coli and Staphylococcus aureus into practical veterinary decision-making. For Escherichia coli , the primary expectation is most often mitigation of disease severity, milk loss and adverse outcomes, rather than complete prevention of clinical mastitis. For Staphylococcus aureus , vaccination may moderately reduce new intramammary infections and shorten infection duration, but responses are herd-specific and depend heavily on transmission control and cow-related factors, including parity. Vaccines are specific, preventive and time-limited. They should therefore be introduced only after pathogen diagnosis, baseline key-performance indicators and management weaknesses have been defined. Their benefits are greatest when vaccination is integrated alongside hygiene, milking management, dry cow management measures, monitoring, treatment and culling strategies.