Long-Term Persistence of IgG Antibodies in recovered COVID-19 individuals at 18 months and the impact of two-dose BNT162b2 (Pfizer-BioNTech) mRNA vaccination on the antibody response (preprint)

This era of emerging variants needs a thorough evaluation of data on the long-term efficacy of immune responses in vaccinated as well as recovered individuals, to understand the overall evolution of the pandemic. In this study, we aimed to assess the dynamics of IgG titers over 18 months in 34 patients from the Umbria region in Italy, who had a documented history of COVID-19 infection in March 2020, and then compared the impact of two-dose BNT162b2 (Pfizer-BioNTech) vaccination on the antibody titers of these patients with the ones who did not receive any dose of vaccine. This is the longest observation (March 2020-September 2021) for the presence of antibodies against SARS-CoV-2 in recovered individuals along with the impact of 2 dose-BNT162b2 vaccination on the titers. Fixed-effect regression models were used for statistical analysis which could be also used to predict future titer trends. At 18 months, 97% participants tested positive for anti-NCP hinting towards the persistence of infection-induced immunity even for the vaccinated individuals. Our study findings demonstrate that while double dose vaccination boosted the IgG titers in recovered individuals 161 times, this boost was relatively short-lived. The unvaccinated recovered individuals, in contrast, continued to show a steady decline but detectable antibody levels. Further studies are required to re-evaluate the timing and dose regimen of vaccines for an adequate immune response in recovered individuals.

Longitudinal observation of antibody responses after SARS-CoV-2 infection at 14 months (preprint)

A better understanding regarding antibody responses against SARS-CoV-2 after natural infection could provide valuable insights into the future implementation of vaccination policies. In this study, we aimed to assess the dynamics of IgG antibody titers in recovered COVID-19 patients over 14 months after mild and moderately severe infection using two FDA-approved immunoassays against SARS-CoV-2 Nucleocapsid protein (NCP)and anti-spike-receptor binding domain (S-RBD) through sequential serological tests at different time points. The demographics and clinical profile, that might be associated with the magnitude and longevity of antibody response were also analyzed. Our results suggest antibody persistency in 31 out of 32 (96.8%) subjects at 14 months post-infection. A significant positive association was observed between disease severity and anti-S-RBD IgG titers at 14 months. Patients who reported a loss of smell and taste during the clinical course of the disease also developed significantly better antibody titers. Patients who were seronegative for anti-NCP IgG (n=7) at 10 months, were found to be seropositive for anti-S-RBD IgG at 12,13 and 14 months emphasizing on higher false-negative rate for N protein-based antibody assays when compared with the anti-S-RBD assays. This study calls for prioritizing vaccination for “naive” individuals (with no previous history of COVID-19 infection) and recovered but antibody-negative individuals instead of “vaccination for all”. This strategy would be helpful in low-resource settings and areas experiencing vaccine shortages by saving time, effort, and assets that could be sourced for the vulnerable populations.

Neutralizing antibody responses 10 months after mild and moderately-severe SARS-CoV-2 infection (preprint)

Improved understanding of immunity offered by the antibodies developed against SARS-CoV-2 is critical. Our study aimed at longitudinal analysis of presence and persistence of neutralizing antibodies over ten months in mild and moderately-severe COVID-19 recovered patients using two immunoassays. Article Summary Line Neutralizing IgG antibody persistency was demonstrated in 63.3% of the subjects (19 out of 30) at ten months post-infection with zero re-infections.

Antibody persistency and dynamic trend after SARS-CoV-2 infection over 8 months (preprint)

Abstract: An improved understanding of the immunity offered by the antibodies developed against SARS-CoV-2 is critical for the development of diagnostic tests and vaccines. Our study aimed at the longitudinal analysis of antibody persistence and its dynamic trend over a period of eight months in a group of COVID-19 recovered patients who tested positive by real-time quantitative PCR for SARS-CoV-2 in the period between the 18th and 30th of March, 2020. The subjects were divided into two groups based on disease severity: mild and moderately-severe. The MAGLUMI 2019-nCoV lgM/lgG chemiluminescent analytical system (CLIA) assay was used to analyse the antibody titres. Robust IgG antibody persistency was demonstrated in 76.7 % of the subjects (23 out of 30) at eight months post infection. The results of this study highlight an important point in terms of the association between humoral immune response and disease severity. Patients who might have experienced a relatively moderate-severe infection may develop a robust immunity that could persist for a longer duration.

A comprehensive analysis of recovered COVID-19 patients and dynamic trend in antibodies over 3 months using ELISA and CLIA methods. (preprint)

Background: Since the Coronavirus disease-2019 outbreak, most studies have focused on etiopathogenic aspects and treatment strategies. Acquired immunity still remains a dilemma. The aim of our study included a comprehensive analysis of patient characteristics, evaluation of antibody response, and its trend over a period of three months in recovered patients. Methods: Monocentric investigator-initiated pilot longitudinal observational study conducted by the Association Naso Sano, on a cohort of 30 COVID recovered patients based in the Umbria region, followed up from April to June 2020 for baseline blood counts, IgM and IgG trends using two different serological assays-ELISA and CLIA. The demographics, blood group, co-morbidities and treatment modalities were recorded from each patient along with an analysis of clinical profile, dates concerning symptom onset, first positive and two consecutive negative swabs using an online questionnaire followed by serological testing. Descriptive and Bivariate (Pearson correlation coefficient) statistics were conducted to detect statistically significant correlations. Findings: The study involved 30 patients with a M:F ratio of 0.57 and a distribution of mild (67%), moderate (30%) and critical (3%). Majority of the patients were healthcare workers (40%) and the mean viral shedding duration was 20.13 +/- 6.17 days. The IgG levels offered long-standing protection as long as 3 months in some cases. A statistically significant, directly proportional correlation (Pearson) exists between ELISA and CLIA values for IgM. Some patients also expressed titers lower than the detection threshold and therefore a positive RT-PCR test does not necessarily guarantee a high IgG response in the recovery period. Interpretation: The data presented in our study provides a relative long-term analysis and possible explanation regarding the protection developed by patients recovered from COVID-19.