**6. The problem of institutional trust**

Public trust in public health systems is critical, and affects the development and maintenance of individual, community and societal health and well-being. This is why health professionals, and especially politicians, need to take the concept of "institutional trust" seriously [29] if they want to improve both the commitment to health among the general population and their public health systems.

Both theoretical and empirical literature show that contemporary societies are built on very low levels of trust [30, 31]. In our societies, there are two types of trust: interpersonal and institutional. Interpersonal trust appears as the result of past interactions by which people learn to make decisions about future interactions; i.e., the individual, from his past experiences, learns whether or not to trust someone else in the future. "Institutional trust" refers to the trust placed by individuals in a system or institution such as a government, a political party, a non-governmental organization, or a particular public or private organization. Institutional trust is based on personal experiences, especially negative ones, that the person has had throughout his or her life, not so much with the institution, but with the people who represent the institution [32]. Research shows that in crisis situations, interpersonal trust tends to increase and institutional trust decreases [33].

Institutional trust is one of the most important concerns when carrying out mass vaccination campaigns [34], not so much because users distrust the public health system, but because they distrust government recommendations [35]. Maintaining institutional trust is critical for mass immunization programs against Covid-19. A clear example of this problem is the low levels of vaccination during the H1N1 pandemic; the lack of trust in the institutions involved in vaccination during the H1N1 pandemic led to an increase in vaccination skepticism. This, together with conspiracy theories, and speculation that the response to the pandemic by governments had been influenced by the commercial interests of big pharma, led to a disastrous failure in immunization levels in most countries [24]. It is clear that in the current period, both interpersonal and institutional trust have undergone changes. Studies point to an increase in interpersonal trust and a decrease in institutional trust during the Covid-19 pandemic [36]. It is necessary to increase the levels of institutional trust when vaccination processes are initiated, both at the first moment, when vaccination is restricted to risk groups, and at the second moment, when vaccines are available for the rest of the population. The recovery of institutional trust will be a key element in achieving vaccination levels that allow herd immunity.
