The level of immunization of children and adolescents under the Protective Vaccination Program in Ukraine is lower than in Poland, and, due to the outbreak of the war in Ukraine, many people now live in conditions that are often unsanitary. Centers for refugees are also places of increased risk of outbreaks of infectious diseases. This risk is increased by the low percentage of the vaccinated, limited access to healthcare (including diagnostics) and overcrowding. The paper presents the state of vaccination in Ukraine against poliomyelitis, measles, diphtheria, tetanus and pertussis, the most important problems in the field of infectious diseases, as well as the resulting risks and the need to prevent them.

In 2008 the WHO published a report on infectious diseases against which there is no effective treatment or vaccines and therefore – diseases able to cause pandemic. In addition, so called disease X was mentioned – potentially deadly, with no herd immunity against it, holding pandemic potential, unknown in medicine yet. In 2019 such disease X was COVID-19. There is a plausibility, that next pandemic will be induced by zoonotic RNA virus (alike SARS-CoV-2) infecting people in place of intensified human-animal contacts (like high-density animal farming) without proper legal regulations in terms of animal husbandry and high population density. Also in the past major pandemics in XX and XXI centuries were result of zoonotic transmissions (HIV/AIDS, SARS, MERS, Spanish flu, avian flu, swine flu, Ebola). The key in risk recognising is governments and international healthcare agencies’ reaction – proper countermeasures to control pandemic range should be taken. Animal trade should be legally regulated and deforestation limited. There is also an urgent need for funding R&D studies on diseases listed by the WHO.