![]() ![]() ![]() ![]() Already in the first part of 2021 the presence of antibodies for at least 8 months was clear. The studies about natural immunity after COVID-19 infection begun in 2020, and showed a variable duration lasting immunity. Further research is needed in order to: (a) measure the durability of immunity over time (b) evaluate both the impacts of Omicron BA.5 on vaccinated and healed subjects and the role of hybrid immunity. Consequently, vaccination of the unvaccinated COVID-19-recovered subjects may not be indicated. Conclusions: this extensive narrative review regarding a vast number of articles highlighted the valuable protection induced by the natural immunity after COVID-19, which seems comparable or superior to the one induced by anti-SARS-CoV-2 vaccination. In general, the severity of the symptoms of reinfection is significantly lower than in the primary infection, with a lower degree of hospitalizations (0.06%) and an extremely low mortality. Vaccine-induced immunity was shown to decay faster than natural immunity. It was highlighted that the vast majority of the individuals after suffering from COVID-19 develop a natural immunity both of cell-mediated and humoral type, which is effective over time and provides protection against both reinfection and serious illness. Results: nearly 900 studies were collected, and 246 pertinent articles were included. Material and Methods: through multiple search engines we investigated COVID-19 literature related to the aims of the review, published since April 2020 through July 2022, including also the previous articles pertinent to the investigated topics. Aims: This narrative review analyzes the literature regarding these two immunitary processes and more specifically: (a) the duration of natural immunity (b) cellular immunity (c) cross-reactivity (d) the duration of post-vaccination immune protection (e) the probability of reinfection and its clinical manifestations in the recovered patients (f) the comparisons between vaccinated and unvaccinated as to the possible reinfections (g) the role of hybrid immunity (h) the effectiveness of natural and vaccine-induced immunity against Omicron variant (i) the comparative incidence of adverse effects after vaccination in recovered individuals vs. Background: Both natural immunity and vaccine-induced immunity to COVID-19 may be useful to reduce the mortality/morbidity of this disease, but still a lot of controversy exists. ![]()
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December 2022
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