Pig farming is a crucial industry worldwide, as pork has become the most consumed meat globally. With the high levels of productivity required by modern pigs, the emergence of new diseases, and the existence of increasingly large and dynamic farms, herd immunity has become an essential aspect of pig production. Herd immunity refers to the resistance of a group of individuals to the invasion and spread of an infectious agent, and it can be measured as the proportion of resistant individuals in the population.
The proportion of resistant individuals in the population is determined by the exposure status before the entry of the specific agent (vaccine or natural infection) and movements in the population (births, deaths, discards, or introductions). Vaccinating more individuals reduces the proportion of susceptible pigs on the farm, and consequently, the number of individuals that can be infected and become infectious.
The goal of disease eradication remains important, although it is rarely achieved. However, trying to eliminate disease can reduce its transmission and frequency, and often its severity. Vaccines play a vital role in improving herd immunity on pig farms. Zimmerman et al. (2012) emphasized that a good vaccination program must begin by defining two crucial aspects: identifying the particular disease risks in a pig farm and considering the effect of maternal immunity and the age of the pigs at the time of vaccination.
In conclusion, herd immunity on pig farms is essential for the industry's sustainability and profitability. Vaccination programs, biosecurity measures, and disease control strategies are essential tools to improve herd immunity and reduce the impact of diseases on pig production.