Preprint Review Version 1 Preserved in Portico This version is not peer-reviewed

SARS-CoV-2 - The Role of Natural Immunity: A Narrative Review

Version 1 : Received: 25 September 2022 / Approved: 28 September 2022 / Online: 28 September 2022 (03:38:36 CEST)

A peer-reviewed article of this Preprint also exists.

Diani, S.; Leonardi, E.; Cavezzi, A.; Ferrari, S.; Iacono, O.; Limoli, A.; Bouslenko, Z.; Natalini, D.; Conti, S.; Mantovani, M.; Tramonte, S.; Donzelli, A.; Serravalle, E. SARS-CoV-2—The Role of Natural Immunity: A Narrative Review. J. Clin. Med. 2022, 11, 6272. Diani, S.; Leonardi, E.; Cavezzi, A.; Ferrari, S.; Iacono, O.; Limoli, A.; Bouslenko, Z.; Natalini, D.; Conti, S.; Mantovani, M.; Tramonte, S.; Donzelli, A.; Serravalle, E. SARS-CoV-2—The Role of Natural Immunity: A Narrative Review. J. Clin. Med. 2022, 11, 6272.

Abstract

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. Aims: This narrative review analyzes the literature about: 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) comparisons between vaccinated and unvaccinated in the possible reinfections; g) the role of hybrid immunity; h) the effectiveness of natural and vaccine-induced immunity against Omicron variant; i) comparative incidence of adverse effects after vaccination in recovered individuals vs. COVID-19-naïve subjects. 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. Results: nearly 900 studies were collected and 238 pertinent articles were included. It was highlighted that the vast majority of individuals after 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. Vaccine-induced immunity was shown to decay faster than natural immunity. 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. Conclusions: this 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. Vaccination of the unvaccinated COVID-19-recovered subjects may not be indicated. Further research is needed in order to: a) measure the durability of immunity over time; b) evaluate both the impacts of Omicron-5 on vaccinated and healed subjects and of hybrid immunity.

Keywords

COVID-19; Sars-CoV-2; Natural immunity; Cellular immunity; Vaccine-induced immunity; Hybrid immunity; Cross-reactivity; Omicron

Subject

Medicine and Pharmacology, Immunology and Allergy

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