Pandemics have always played a relevant role in human history, affecting daily life as health, demographic, economicand social levels. Before the emergence of SARS-CoV-2, people had to face a large number of pandemics. The retrospective of the last century tells us about 6 pandemics. The first pandemic began in 1916 and caused Encephalitis lethargica, an infectious disease that affected around 5 million people. We are also aware of four influenza pandemics: in 1918, 1957, 1968 and 1977. The last three took place in the era of modern virology and have been best described. All 4 have been informally identified, based on their presumed places of origin, as Spanish, Asian, Hong Kong and Russian flu respectively. The death toll from all these infections is approaching 100 million people. Much attention is paid to pandemics caused by the influenza virus, but we should not overlook the fact that for more than half a century, mankind has been struggling with the human immunodeficiency virus. In that time, the disease has not been conquered, although antiretroviral therapy has slowed the progression of the disease.In total, HIV/AIDS has killed more than 35,000,000 people to date and continues to claim victims every day until a solution is found to eradicate the infection. The experience of the last century, but also that of the current century is a warning sign for the future generations. What we can see is that the frequency of pandemics increases from year to year, while the resistance of the medical system not being sufficient to neutralize the consequences. We will probably have to face new infectious diseases more and more often, and they will take on more and more common dimensions. Events of the past and present lead us to be prepared for the unpredictable. Each of us must be aware that quarantine, hand washing, wearing masks or public education will not solve the problem. The key to solving it is vaccination. As long as we do not realize this, the battle between humans and microorganisms will be ongoing.