Europe is experiencing a third wave of COVID-19 due to the spread of highly transmissible SARS-CoV-2 variants. A number of positive and negative factors constantly shape the rates of COVID-19 infections, hospitalization, and mortality. Among these factors, the rise in increasingly transmissible variants on one side and the effect of vaccinations on the other side create a picture deeply different from that of the first pandemic wave. Starting from the observation that in several European countries the number of COVID-19 infections in the second and third pandemic wave increased without a proportional rise in disease severity and mortality, we hypothesize the existence of an additional factor influencing SARS-CoV-2 dynamics. This factor consists of an immune defence against severe COVID-19, provided by SARS-CoV-2-specific T cells progressively developing upon natural exposure to low virus doses present in populated environments. As suggested by recent studies, low-dose viral particles entering the respiratory and intestinal tracts may be able to induce T cell memory in the absence of inflammation, potentially resulting in different degrees of immunization. In this scenario, non-pharmaceutical interventions would play a double role, one in the short term by reducing the detrimental spreading of SARS-CoV-2 particles, and one in the long term by allowing the development of a widespread (although heterogeneous and uncontrollable) form of immune protection.
【저자키워드】 COVID-19, SARS-CoV-2, protective immunity, T cell responses, facial masking, fomites, environmental exposure, memory T cells, 【초록키워드】 Inflammation, Europe, vaccination, pandemic, Mortality, severe COVID-19, Hospitalization, T cells, disease severity, Intervention, virus, immunization, immune, Spread, T cell, Viral, COVID-19 infection, SARS-CoV-2 variants, low-dose, Factors, respiratory, SARS-CoV-2-specific T cells, immune protection, Vaccinations, dose, SARS-CoV-2 dynamics, detrimental, long term, exposure to, short term, observation, Factor, COVID-19 infections, heterogeneous, intestinal tract, positive, SARS-CoV-2 particles, T cell memory, viral particle, starting, widespread, European country, resulting, provided, absence, reducing, suggested, induce, increasingly, SARS-CoV-2-specific T cell, transmissible variant, 【제목키워드】 protection,