The magnitude and the quality of humoral responses against SARS-CoV-2 have been associated with clinical outcome. Although the elicitation of humoral responses against different
viral proteins is rapid and occurs in most infected individuals, its magnitude is highly variable among them and positively correlates with
COVID-19 disease severity. This rapid response is characterized by the almost concomitant appearance of virus-specific
IgG,
IgA and
IgM antibodies that contain
neutralizing antibodies directed against different
epitopes of the Spike
glycoprotein. Of particularly interest, the
antibodies against domain of the Spike that interacts with the cellular receptor ACE2, known as the receptor binding domain (RBD), are present in most infected individuals and are block viral entry and infectivity. Such
neutralizing antibodies protect different animal species when administered before virus exposure; therefore, its elicitation is the main target of current
vaccine approaches and their clinical use as recombinant
monoclonal antibodies (mAbs) is being explored. Yet, little information exists on the duration of humoral responses during natural
infection. This is a key issue that will impact the management of the pandemic and determine the utility of seroconversion studies and the level of herd immunity. Certainly, several cases of
reinfection have been reported, suggesting that immunity could be transient, as reported for other coronaviruses. In summary, although the kinetics of the generation of
antibodies against SASR-CoV-2 and their protective activity have been clearly defined, their role in
COVID-19 pathogenesis and the length of these responses are still open questions.