Durability of Humoral Immune Responses to SARS-CoV-2 in Citizens of Ariano Irpino (Campania, Italy): A Longitudinal Observational Study With an 11.5-Month Follow-Up

Abstract

As of November 17, 2021, SARS-CoV-2 (Severe Acute Respiratory Syndrome CoronaVirus 2), the causative agent of COVID-19 (COronaVIrus Disease 19), has infected ~250 million people worldwide, causing around five million deaths. Titers of anti-SARS-CoV-2 neutralizing antibodies were relatively stable for at least 9 months in a population-based study conducted in Wuhan, China, both in symptomatic and in asymptomatic individuals. In the mass screening campaign conducted in the town of Ariano Irpino (Avellino, Italy) in May, 2020, 5.7% (95% CI: 5.3-6-1) of the 13,444 asymptomatic citizens screened were positive for anti-nucleocapsid antibodies against SARS-CoV-2. Among these, 422 citizens were re-tested for anti SARS-CoV-2 antibodies in January, 2021 and/or in April, 2021 and enrolled in this longitudinal observational study. Median (interquartile range) age of the study cohort was 46 years (29–59), with 47 (11.1%) participants of minor age, while 217 (51.4%) participants were females. There was no evidence of re-infection in any of the subjects included. Presence of anti-nuclear antibodies antibodies (Elecysis, Roche) was reported in 95.7 and 93.7% of evaluable participants in January and April, 2021. Multiple logistic regression analysis used to explore associations between age, sex and seroprevalence showed that adults vs. minors had significantly lower odds of having anti-S1 antibodies (Biorad) both in January, 2021 and in April, 2021. Our findings showed that antibodies remained detectable at least 11.5 months after infection in >90% of never symptomatic cases. Further investigation is required to establish duration of immunity against SARS-CoV-2.

Risk of SARS-CoV-2 Reinfection 18 Months After Primary Infection: Population-Level Observational Study

“…This study confirms and expands previous findings reporting a low risk of SARS-CoV-2 reinfection, and a very low risk of severe or lethal COVID-19 for those who recovered from primary infection ( 3 , 12 , 13 ), suggesting that the protection conferred by the natural immunity lasts beyond 12 months. Although the marked increase of the reinfection rates during the Omicron wave is concerning, the risk of a secondary severe disease or death remained close to zero.…”

Risk of reinfection and disease afterSARS‐CoV‐2 primary infection: Meta‐analysis

“…Of the 3282 papers initially retrieved, we included 91 cohort studies evaluating the onset of reinfection, severe and very severe/lethal COVID‐19 among 15,034,624 previously infected subjects (Figure 1), either among health care workers (27 publications; n = 37,598 2,8,9,15,17,24,36,38,42–59 ) or in the general population (67 publications; n = 14,997,026 3–7,10,12,16–23,25–27,43,49,60–106 ).…”

“…As shown in Table S1, most of the included studies ( n = 43) were carried out in Europe, 2,4–10,12,15,17,18,21,24,26,36,38,44,46–51,58,66,69,71,72,75,81,85–88,91–93,95,99,102 24 in the USA, 20,22,23,25,42,43,57,59,63,67,77,79,82–84,89,90,97,98,103,105–107 18 in Asia 3,16,19,27,45,52–54,56,60,62,64,65,70,73,74,100,101 and the remaining six in South America or South Africa 61,68,80,94,96,104 . The mean age of the participants ranged from 15 to 87 years, and the average follow‐up ranged from 29 to 371 days.…”

“…Overall, a total of 158,478 reinfections were recorded among the 15,034,624 subjects with a previous infection, 2–10,12,13,15–27,36,38,42–107 corresponding to a pooled rate of 0.97% (95% CI: 0.71%–1.27%—Table 1; Figure 2). The summary rate of reinfection rose to 1.07% (95% CI: 0.73%–1.46%) when only the 69 datasets with a more conservative time lag of ≥90 days between the two episodes were considered 3–6,8–10,12,18–23,25,26,36,42–44,46–50,52–56,59,61–65,67–69,72–84,86,87,89,91–96,98,101,103,105–107 and it slightly varied by reinfection definition criteria (0.93% vs 1.01% when considering studies with high vs low risk of misclassification). The risk of reinfection was higher among health care workers as compared to the general population (1.20% vs 0.90), and among females (0.79% vs 0.55% among males), although these estimates showed largely overlapping confidence intervals.…”

“…In the 59 available datasets, 2,3,5,6,10,16–22,25–27,36,44,46–59,63–67,69,71–74,79,82,84–87,90,93–95,99–104 a total of 1380 severe COVID‐19 diseases were diagnosed among 5,006,604 subjects with a previous infection, corresponding to a pooled rate of 0.02% (95% CI: 0.00%–0.04%—Table 1). This rate did not substantially vary when only the studies with longer time lag were considered, while it increased—still, however, remaining below 0.1%—when only the studies that used CDC criteria to define reinfections were included (summary rate 0.07%; 0.04%–0.10%).…”