Influenza vaccination: from epidemiological aspects and advances in research to dissent and vaccination policies.

Influenza is a serious public health problem, since seasonal epidemics affect approximately 5-10% of the population and thus give rise to a heavy social and healthcare burden. The heavy burden of disease is due to several factors, one of which is the biological features of the pathogen. Indeed influenza viruses display high mutation rates and undergo frequent genetic reassortment. Minor variations cause seasonal epidemics and major variations, which result from the hybridization of viruses typical of different animal species, can lead to pandemics. Vaccination remains the most efficacious means of mitigating the harmful healthcare and social effects of influenza. Influenza vaccines have evolved over time in order to offer broader protection against circulating strains. Trivalent vaccines containing two A viruses and one B virus are currently available. However, given the co-circulation of both B virus lineages (B/Yamagata and B/Victoria), quadrivalent vaccines have recently been developed. The new quadrivalent vaccines constitute a great advance, in that they can offer broader strain coverage. Despite the availability of effective and safe influenza vaccines, the Italian public's trust in vaccination has declined and, in the last few years, influenza vaccination coverage rates have decreased both among the elderly and among at-risk adults. It is therefore necessary that users, in their own interests, regain trust in this important means of disease prevention. In order to mitigate the damage wreaked by influenza, it seems important to: (i) improve clinical-epidemiological and virological surveillance of the disease; (ii) promote the development of new efficacious vaccines, as has recently been done through the introduction of the quadrivalent vaccine; (iii) extend free vaccination to the entire population, as in the US and Canada; (iv) ensure that general healthcare professionals are properly informed and always updated with regard to vaccination; (v) promote public campaigns to raise the population's awareness of the importance of vaccination; (vi) inform politicians and other decision-makers of scientific results in the field of vaccination; (vii) fight the antivaccination lobbies with every available weapon.