Lessons learned from Covid-19 outbreak

Covid-19 is a disease caused by the SARS-CoV-2 virus and, for the past two and a half years, has been driving a worldwide pandemic. The pandemic has a broad spectrum of effects ranging from increased patient morbidity and mortality to impacting the global economy. The primary determinant in reducing this impact has been the rapid development of vaccines. Before vaccination was available the only way to cope with Covid-19 was social restrictions intended to limit the transmission of SARS-CoV-2. These was found to be associated with decreased rates of other communicable diseases. Accordingly, after easing social restrictions (e.g. mask mandates) infection Incidence Rates (IRs) were rebounding. However, the social distancing created a unique opportunity for us to reveal the potential causal association between respiratory viruses and other pathogens, e.g., community acquired alveolar pneumonia (CAAP). Following the reemergence of respiratory viruses, we could show that certain respiratory viruses: influenza A, RSV, HMPV, and PFV, but not adenovirus or rhinovirus, were strongly associated with CAAP in young children.

One of the main issues of concern for human health, is to identify novel correlates of protection (COPs) against symptomatic SARS-CoV-2 infection in vaccinated individuals. To tackle this question a multicenter prospective cohort study was conducted to assesses the association between different serological profiles, neutralization assays and risk for SARS-CoV-2 infection, comparing those vaccinated with three doses of Pfizer-BioNTech vaccine to those who received the fourth dose. The fourth dose of the vaccine elicited a significant rise in antibody binding and neutralizing titers to multiple variants including omicron. Nevertheless, in healthy adults, receiving three or four doses of vaccine, combinations of baseline IgA and IgG antibody levels to SARS-CoV-2 variant of concerns are associated with protection from symptomatic infection. On the other hand, we identified a subpopulation of healthy adult individuals with low-baseline levels of antibodies against SARS-CoV-2, which are at an increased risk for SARS-CoV-2 infection despite receiving three or four doses of the Pfizer-BioNTech vaccine.