Il Rischio Di Reinfezione Da Sars-Cov-2 E Le Implicazioni Per La Diagnostica

ABSTRACT

One of the most interesting aspects of the COVID-19 pandemic is that a variable percentage of patients (from 2% to 69%) could have a repeated positivity following hospital discharge or even several weeks after clinical recovery (1). There are multiple reasons why a positive result to SARS-CoV-2, usually ascertained by RT-PCR, may be detected again, including reinfection, disease reactivation, prolonged viral shedding or false positive results (1-2). Since the beginning of the pandemic, several authors have reported the possibility of reinfection by SARS-CoV-2 or reactivation of a latent infection, calling for urgent attention from researchers, as well as public health policymakers. In our study we estimate incidence rate of 3.5% of reinfection in the Province of Modena in the first 6 months of 2021. Reinfection rates according to vaccinated or non-vaccinated subjects were 0.6% vs 1.1% (p<0.0001). Multiple questions regarding reinfection associated with SARS-CoV-2 are still ongoing. What is the pathophysiological mechanism for reinfection? Who are the subjects with a higher risk of reinfection? What is the clinical burden for reinfected patients? Reinfection with the SARS-CoV-2 virus can be mainly attributed to two phenomena decay of the immune response and viral mutations that favor the appearance of new variants (3-5). Currently, there are discordant rates of reinfection reported in SRs (ranging from 0-50%), which could partially be explained by the heterogeneous adopted definitions of reinfection. Today, there is still no universal agreement on the determination of the correct time period between positive results for SARS-CoV-2 for the definition of reinfection, although the definition provided by CDC is the most accredited (https//www.cdc.gov/ coronavirus/2019-ncov/php/invest-criteria.html). It has been pointed out that the severity of reinfection depends on the individual immune response, as well as both the viral load and the SARS-CoV-2 variants causing the reinfection. New virus variants could evade immune responses acquired in subjects with infections from previous variants or reduce the capacity for neutralization by polyclonal antibodies (4). This issue suggests the need to increase the current knowledge about the degree of protection provided against SARS-CoV-2, leading the development of vaccines and the creation and implementation of appropriate interventional strategies. Because COVID-19 is a relatively new disease, several aspects of its progression and long-term health effects are unknown, one of the aspects that have become more relevant as time goes by is the impact that reinfections. There is a real, albeit rare risk of SARS-CoV-2 reinfection. Nevertheless, a standardized approach to identify and report reinfection cases should be developed.