Long-Term Persistence of Anti-SARS-CoV-2 Antibodies in a Pediatric Population

Evaluating Immunologic and Illness Outcomes of SARS-CoV-2 Infection in Vaccinated and Unvaccinated Children Aged ≥ 5 Years, in a Multisite Longitudinal Cohort

Hybrid immunity, as a result of infection and vaccination to SARS-CoV-2, has been well studied in adults but limited evidence is available in children. We evaluated the antibody responses to primary SARS-CoV-2 infection among vaccinated and unvaccinated children aged ≥ 5 years.

METHODS

A longitudinal cohort study of children aged ≥ 5 was conducted during August 2021-August 2022, at sites in Arizona, Texas, Utah, and Florida. Children submitted weekly nasal swabs for PCR testing and provided sera 14-59 days after PCR-confirmed SARS-CoV-2 infection. Antibodies were measured by ELISA against the receptor-binding domain (RBD) and S2 domain of ancestral Spike (WA1), in addition to Omicron (BA.2) RBD, following infection in children, with and without prior monovalent ancestral mRNA COVID-19 vaccination.

RESULTS

Among the 257 participants aged 5 to 18 years, 166 (65%) had received at least two mRNA COVID-19 vaccine doses ≥ 14 days prior to infection. Of these, 53 occurred during Delta predominance, with 37 (70%) unvaccinated at the time of infection. The remaining 204 infections occurred during Omicron predominance, with 53 (26%) participants unvaccinated. After adjusting for weight, age, symptomatic infection, and gender, significantly higher mean RBD AUC values were observed among the vaccinated group compared to the unvaccinated group for both WA1 and Omicron (p < 0.0001). A smaller percentage of vaccinated children reported fever during illness, with 55 (33%) reporting fever compared to 44 (48%) unvaccinated children reporting fever (p = 0.021).

CONCLUSIONS

Children with vaccine-induced immunity at the time of SARS-CoV-2 infection had higher antibody levels during convalescence and experienced less fever compared to unvaccinated children during infection.

Deciphering the Longevity and Levels of SARS-CoV-2 Antibodies in Children: A Year-Long Study Highlighting Clinical Phenotypes and Age-Related Variations

BACKGROUND

Identifying potential factors correlated with the sustained presence of antibodies in plasma may facilitate improved retrospective diagnoses and aid in the appraisal of pertinent vaccination strategies for various demographic groups. The main objective was to describe the persistence of anti-spike IgG one year after diagnosis in children and analyse its levels in relation to epidemiological and clinical variables.

METHODS

A prospective, longitudinal, observational study was conducted in a university reference hospital in the Metropolitan Region of Barcelona (Spain) (March 2020-May 2021). This study included patients under 18 years of age with SARS-CoV-2 infection (positive PCR or antigen tests for SARS-CoV-2). Clinical and serological follow-up one year after infection was performed.

RESULTS

We included 102 patients with a median age of 8.8 years. Anti-spike IgG was positive in 98/102 (96%) 12 months after the infection. There were higher anti-spike IgG levels were noted in patients younger than 2 years (p = 0.034) and those with pneumonia (p < 0.001). A positive and significant correlation was observed between C-reactive protein at diagnosis and anti-spike IgG titre one-year after diagnosis (p = 0.027).

CONCLUSION

Anti-SARS-CoV-2 IgG antibodies were detected in almost all paediatric patients one year after infection. We also observed a positive correlation between virus-specific IgG antibody titres with SARS-CoV-2 clinical phenotype (pneumonia) and age (under 2 years old).

Pediatric antibody responses to SARS-CoV-2 after infection and vaccination in Calgary, Canada

BACKGROUND

There are few reports of longitudinal serologic responses in children following Sars-CoV-2 infection and vaccination. This study describes longitudinal SARS-CoV-2 antibody responses following infection, vaccination, or both (hybrid immunity) in a cohort of Canadian children. The objectives of our study were to compare antibody levels following SARS-CoV-2 infection, vaccination, and hybrid immunity and to examine antibody decline after final antigen exposure.

METHODS

The Alberta Childhood COVID-19 Cohort (AB3C) study was a prospective longitudinal cohort study conducted from July 2020 to September 2022 with repeat sampling across 5 visits. Children under 18 years of age were enrolled for serial measurement of antibody responses to SARS-CoV-2 virus vaccine and infection.

RESULTS

The final sample size was 919; participants were 50.5% female, 48.2% were > 12 years and 88.5% were white ethnicity. The median peak spike IgG level of those with only infection was not different from those with no vaccination or infection (233 AU/mL (IQR: 99-944 AU/mL) vs. 3 AU/mL (IQR: 1-5 AU/mL; P = 0.1765). Participants with infections after vaccination had higher IgG levels than those where infection preceded vaccination (median: 36,660 (IQR: 22,084 - 40,000 AU/mL) vs. 17,461 AU/mL (IQR: 10,617 - 33,212 AU/mL); P < 0.0001). In a linear mixed methods model, children with infection-only had low levels of antibody that stayed stable over the study duration without further antigen exposures. Those with infection after vaccination had the slowest rate of antibody decline over time at 4% (95%CI: 2-5%) per week, compared with children where infection preceded vaccine 7% (95%CI: 6-8%) per week.

CONCLUSIONS

Children with hybrid immunity conferred through vaccination (2 + doses) followed by a SARS-CoV-2 infection had the highest and longest lasting antibody levels, compared to children who had an infection followed by vaccination, vaccination-only, or infection-only. The longer-term clinical importance of these findings, related to prevention of repeated infections and severe outcomes and need for further vaccine doses, is not yet known.

SARS-CoV-2 Antibody Kinetics in Unvaccinated Hospitalized Children With COVID-19

BACKGROUND

Antibody levels decline a few months post-acute COVID-19, but humoral memory persists in adults. Age and disease severity may affect antibody responses. This study aims to evaluate the presence and durability of antibody responses in children with COVID-19.

METHODS

A prospective, single-center study, involving unvaccinated children 0-16 years of age who were hospitalized with COVID-19 between October 2020 and December 2021, was conducted. Serological testing for anti-Spike severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG and neutralizing antibodies was performed at diagnosis and at 1-, 3-, 6- and 12-months post-infection.

RESULTS

A total of 65 immunocompetent children were enrolled [mean age (±SD): 6.7 (±6.4) years; males: 56.9%]. At 3 months, 40/44 (91%) children were seropositive; seropositivity persisted in 22/26 (85%) children at 6 months and in 10/12 (83%) children at 12 months. There was no evidence that age was modifying the prediction of variance of SARS-CoV-2 IgG levels. In contrast, SARS-CoV-2 IgG levels varied with time and disease severity. The association with time was non-linear, so that with increasing time there was a significant reduction in SARS-CoV-2 IgG levels [coef, 0.044 (95% confidence interval {CI}: 0.061-0.028), P < 0.001]. For each increment of time, the higher disease severity group was associated with 0.9 lower SARS-CoV-2 IgG levels. Everyone varied from the average effect of time with an SD of 0.01, suggesting that individuals may have different trajectories across time.

CONCLUSION

Disease severity, but not age, influences antibody titers among children hospitalized with COVID-19. SARS-CoV-2 infection induces durable seroconversion in these children with detectable IgG levels at 1 year after infection.

SARS-CoV-2 Seroepidemiology and Antibody Levels in Children during BA.5 Predominance Period

This is a SARS-CoV-2 seroepidemiological study in a pediatric population (0-16 years) during the BA.5 Omicron predominance period in the Athens metropolitan area. Serum samples were tested for SARS-CoV-2 nucleocapsid antibodies (Abs-N), representing natural infection during three periods of BA.5 predominance: 1 May 2022-31 August 2022 (period A), 1 September 2022-31 December 2022 (period B), and July 2023 (period C). Εpidemiological data were also collected. Additionally, in period C, Abs-N-seronegative samples were tested for SARS-CoV-2 spike antibodies (Abs-S). A total of 878 children were tested (males: 52.6%), with a median age (IQR) of 96 (36-156) months; the number of cases of seropositivity during the three periods were as follows: A: 292/417 (70%), B: 288/356 (80.9%), and C: 89/105 (84.8%), with p < 0.001. SARS-CoV-2 seropositivity increased from period A to C for children 0-1 year (p = 0.044), >1-4 years (p = 0.028), and >6-12 years (p = 0.003). Children > 6-12 years had the highest seropositivity rates in all periods (A: 77.3%, B: 91.4%, and C: 95.8%). A significant correlation of monthly median Abs-N titers with monthly seropositivity rates was detected (rs: 0.812, p = 0.008). During period C, 12/105 (11.4%) Abs-S-seropositive and Abs-N-seronegative samples were detected and total seropositivity was estimated at 96.2% (101/105). The findings of this study indicate a high SARS-CoV-2 exposure rate of children during the BA.5 predominance period and suggest that in future seroepidemiological studies, both antibodies should be tested in Abs-N-seronegative populations.

Exploring the long-term seroprevalence of SARS-CoV-2 antibodies in infants born to women with clinical or laboratory-confirmed COVID-19

INTRODUCTION

Infants are at a higher risk of severe illness with COVID-19 infection compared to older children. While COVID-19 vaccination is not recommended for young infants, they can acquire maternally-derived anti-SARS-CoV-2 antibodies passively through the placenta and breastmilk. We described the persistence of infection-induced maternal antibodies in infant circulation at 9-12 months of age.

METHODOLOGY

This was a cross-sectional study nested within the INTERCOVID multinational cohort study. For each COVID positive pregnant woman, two unmatched consecutive COVID negative pregnant women were enrolled between April and September 2020. Women with a positive PCR test, radiographic signs consistent with COVID-19, or at least 2 predefined symptoms of COVID-19 were considered as COVID positive. For this nested cross-sectional study, all COVID positive and either one of the COVID negative participants recruited from the Aga Khan University, Pakistan were approached 9-12 months after delivery, and maternal and infant sera were collected for antibody detection.

RESULTS

Altogether, 83 mothers provided consent, of whom 32 (38.6 %) were COVID positive and 51 (61.4 %) were COVID negative during pregnancy. Anti-SARS-CoV-2 antibodies were present in 13 (41 %) infants born to COVID positive and 19 (39 %) infants born to COVID negative mothers (p = 0.87). The presence of reactive antibodies in infants at follow-up was associated with maternal antibodies at follow-up (OR:9.50, 95 % CI:2.03-44.42; p = 0.004). COVID infection occurred in 3 (6 %) infants born to COVID negative mothers while no infant born to a COVID positive mother had a history of infection (p = 0.27).

CONCLUSION

The presence of reactive anti-SARS-CoV-2 antibodies in infants at 9-12 months of age is associated with maternal seropositivity 9-12 months after delivery rather than maternal infection during pregnancy. Further studies are required to validate these findings and assess whether passive immunity in infants is protective against COVID-19 infection.

SARS-CoV-2 Seroprevalence in a Berlin Kindergarten Environment: A Cross-Sectional Study, September 2021

SARS-CoV-2 serology may be helpful to retrospectively understand infection dynamics in specific settings including kindergartens. We assessed SARS-CoV-2 seroprevalence in individuals connected to kindergartens in Berlin, Germany in September 2021. Children, staff, and household members from 12 randomly selected kindergartens were interviewed on COVID-19 history and sociodemographic parameters. Blood samples were collected on filter paper. SARS-CoV-2 anti-S and anti-N antibodies were assessed using Roche Elecsys. We assessed seroprevalence and the proportion of so far unrecognized SARS-CoV-2 infections. We included 277 participants, comprising 48 (17.3%) kindergarten children, 37 (13.4%) staff, and 192 (69.3%) household members. SARS-CoV-2 antibodies were present in 65.0%, and 52.7% of all participants were vaccinated. Evidence of previous infection was observed in 16.7% of kindergarten children, 16.2% of staff, and 10.4% of household members. Undiagnosed infections were observed in 12.5%, 5.4%, and 3.6%, respectively. Preceding infections were associated with facemask neglect. In conclusion, two-thirds of our cohort were SARS-CoV-2 seroreactive in September 2021, largely as a result of vaccination in adults. Kindergarten children showed the highest proportion of non-vaccine-induced seropositivity and an increased proportion of previously unrecognized SARS-CoV-2 infection. Silent infections in pre-school children need to be considered when interpreting SARS-CoV-2 infections in the kindergarten context.

Distinct T cell polyfunctional profile in SARS-CoV-2 seronegative children associated with endemic human coronavirus cross-reactivity

SARS-CoV-2 infection in children typically results in asymptomatic or mild disease. There is a paucity of studies on SARS-CoV-2 antiviral immunity in African children. We investigated SARS-CoV-2-specific T cell responses in 71 unvaccinated asymptomatic South African children who were seropositive or seronegative for SARS-CoV-2. SARS-CoV-2-specific CD4+ T cell responses were detectable in 83% of seropositive and 60% of seronegative children. Although the magnitude of the CD4+ T cell response did not differ significantly between the two groups, their functional profiles were distinct, with SARS-CoV-2 seropositive children exhibiting a higher proportion of polyfunctional T cells compared to their seronegative counterparts. The frequency of SARS-CoV-2-specific CD4+ T cells in seronegative children was associated with the endemic human coronavirus (HCoV) HKU1 IgG response. Overall, the presence of SARS-CoV-2-responding T cells in seronegative children may result from cross-reactivity to endemic coronaviruses and could contribute to the relative protection from disease observed in SARS-CoV-2-infected children.

An exploratory study of children with caries and its relationship to SARS-CoV-2

This exploratory study investigated whether children with dental decay were more likely to have COVID-19 than those without caries. The children underwent dental inspection and blood collection for detection of SARS-CoV-2 antibodies. Fifty-four children aged 6 to 9 years participated in the survey, which was conducted between March and June 2020 in the municipality of Ipojuca, Pernambuco, Brazil. The diagnosis of caries was performed using the dmft and DMFT indices. Parents reported signs and symptoms of sickness in their children during this period. The serology test aimed to verify the immune response of the children to coronavirus by detecting IgM/IgG antibodies. Statistical analyses were performed at P < 0.05. The majority of the children presented caries (68.5%). Of the nine children who tested positive for COVID-19 (16.7%), eight presented IgG antibodies to the virus, and only one had IgG and IgM antibodies to SARS-CoV2. Children who tested positive for SARS-CoV-2 had a higher percentage of caries lesions than those who tested negative for SARS-CoV-2 (77.8% vs 65.9%), but this difference was not statistically significant.

Persistent humoral immune response in youth throughout the COVID-19 pandemic: prospective school-based cohort study

Understanding the development of humoral immune responses of children and adolescents to SARS-CoV-2 is essential for designing effective public health measures. Here we examine the changes of humoral immune response in school-aged children and adolescents during the COVID-19 pandemic (June 2020 to July 2022), with a specific interest in the Omicron variant (beginning of 2022). In our study "Ciao Corona", we assess in each of the five testing rounds between 1874 and 2500 children and adolescents from 55 schools in the canton of Zurich with a particular focus on a longitudinal cohort (n=751). By July 2022, 96.9% (95% credible interval 95.3-98.1%) of children and adolescents have SARS-CoV-2 anti-spike IgG (S-IgG) antibodies. Those with hybrid immunity or vaccination have higher S-IgG titres and stronger neutralising responses against Wildtype, Delta and Omicron BA.1 variants compared to those infected but unvaccinated. S-IgG persist over 18 months in 93% of children and adolescents. During the study period one adolescent was hospitalised for less than 24 hours possibly related to an acute SARS-CoV-2 infection. These findings show that the Omicron wave and the rollout of vaccines boosted S-IgG titres and neutralising capacity. Trial registration number: NCT04448717. https://clinicaltrials.gov/ct2/show/NCT04448717 .

The Detection of SARS-CoV-2 Antibodies in an Exposed Human Population Is Biased by the Immunoassay Used: Implications in Serosurveillance

The presence of SARS-CoV-2 antibodies was examined over 7 months in a population of essential service workers exposed during the first epidemic wave in Madrid (Spain). Results obtained with different serological assays were compared. Firstly, serum samples obtained in April 2020 were analyzed using eleven SARS-CoV-2 antibody detection methods, including seven ELISAs, two CLIAs and two LFAs. While all of the ELISA tests and the Roche eCLIA method showed good performance, it was poorer for the Abbott CLIA and LFA tests. Sera from 115 workers with serologically positive results in April were collected 2 and 7 months after the first sampling and were analyzed using five of the tests previously assessed. The results showed that while some ELISA tests consistently detected the presence of anti-SARS-CoV-2 antibodies even 7 months after first detection, other methods, such as the Abbott CLIA test, showed an important reduction in sensitivity for these mature antibodies. The sensitivity increased after establishing new cut-off values, calculated taking into account both recent and old infections, suggesting that an adjustment of assay parameters may improve the detection of individuals exposed to the infection.

Behavior of immunoglobulin G antibodies for SARS-COV-2 in Mexican pediatric patients with comorbidities: a prospective comparative cohort study

Background

More than two years after the pandemic of COVID-19 caused by the severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) there is a great lack of information. The presence of immunoglobulin G (IgG) have been related with disease severity. Patients with comorbidities could develop more severe infection; however, the evaluation of the humoral response in pediatric population are needed especially in patients with comorbidities. Our aim was to describe the behavior of IgG in pediatric patients and to know if there is a difference between patients with comorbidities.

Methods

A prospective comparative cohort study was carried out in a single center from June 2020 to January 2021, with a follow-up of 6 months. The study included all the subjects with confirmatory test for SARS-CoV-2 from 1 month to 17 years 11 months, the follow-up of the disease's evolution and measurement of IgG antibodies was collected. We obtained the clinical data, and comorbidities like arterial hypertension, diabetes, obesity, and cancer, the initial symptoms were recorded as well as the evolution regarding the severity of COVID-19 and the need for hospitalization, intensive care unit or mechanical ventilation. The follow up was carried out through medical consultation with an appointment every month that included direct interrogation, examination, and peripheral blood collection for the IgG quantification. The antibodies detection was done through peripheral blood and chemiluminescence microparticle immunoassay.

Results

A total of 237 patients with positive polymerase chain reaction (PCR) for SARS-COV-2 were included, of which 147 presented IgG antibodies (62%), 112 (76%) without comorbidity and 35 (24%) with comorbidities, by the sixth month only 2.7% continue with positive antibody measurements. Patients with comorbidities reach higher IgG levels than patients without comorbidities the basal titters were: 5.17 for patients without comorbidities vs. 6.96 for the group with comorbidities (P<0.001).

Conclusions

We found an association between the presence of comorbidities and high levels of IgG units in pediatric patients with COVID-19. Additionally, patients with more severe course of the disease have higher levels of IgG and by the third month less than 35% have immunity.

Prevalence and risk factor for long COVID in children and adolescents: A meta-analysis and systematic review

BACKGROUND

Millions of COVID-19 pediatric survivors are facing the risk of long COVID after recovery from acute COVID-19. The primary objective of this study was to systematically review the available literature and determine the pooled prevalence of, and risk factors for long COVID among the pediatric survivors.

METHODS

Studies that assessed the prevalence of, or risk factors associated with long COVID among pediatric COVID-19 survivors were systematically searched in PubMed, Embase, and Cochrane Library up to December 11th, 2022. Random effects model was performed to estimate the pooled prevalence of long COVID among pediatric COVID-19 patients. Subgroup analyses and meta-regression on the estimated prevalence of long COVID were performed by stratification with follow-up duration, mean age, sex ratio, percentage of multisystem inflammatory syndrome, hospitalization rate at baseline, and percentage of severe illness.

RESULTS

Based on 40 studies with 12,424 individuals, the pooled prevalence of any long COVID was 23.36 % ([95 % CI 15.27-32.53]). The generalized symptom (19.57 %, [95 % CI 9.85-31.52]) was reported most commonly, followed by respiratory (14.76 %, [95 % CI 7.22-24.27]), neurologic (13.51 %, [95 % CI 6.52-22.40]), and psychiatric (12.30 %, [95% CI 5.38-21.37]). Dyspnea (22.75 %, [95% CI 9.38-39.54]), fatigue (20.22 %, [95% CI 9.19-34.09]), and headache (15.88 %, [95 % CI 6.85-27.57]) were most widely reported specific symptoms. The prevalence of any symptom during 3-6, 6-12, and> 12 months were 26.41 % ([95 % CI 14.33-40.59]), 20.64 % ([95 % CI 17.06-24.46]), and 14.89 % ([95 % CI 6.09-26.51]), respectively. Individuals with aged over ten years, multisystem inflammatory syndrome, or had severe clinical symptoms exhibited higher prevalence of long COVID in multi-systems. Factors such as older age, female, poor physical or mental health, or had severe infection or more symptoms were more likely to have long COVID in pediatric survivors.

CONCLUSIONS

Nearly one quarter of pediatric survivors suffered multisystem long COVID, even at 1 year after infection. Ongoing monitoring, comprehensive prevention and intervention is warranted for pediatric survivors, especially for individuals with high risk factors.

Quantitative Antibody Levels Against SARS-CoV-2 Spike Protein in COVID-19 and Multisystem Inflammatory Syndrome in Children

The majority of children with coronavirus diseases 2019 (COVID-19) are asymptomatic or develop mild symptoms, and a small number of patients require hospitalization. Multisystem inflammatory syndrome in children (MIS-C) is one of the most severe clinical courses of COVID-19 and is suggested to be a hyperinflammatory condition. This study aimed to compare quantitative antibody levels against SARS-CoV-2 spike protein in children with COVID-19 and MIS-C. Blood samples from 75 patients [n = 36 (48%) with mild/asymptomatic (group 1), n = 22 (29.3%) with moderate-to-severe SARS-CoV-2 infection (group 2) and n = 17 (22.6%) patients with MIS-C (group 3)] were analyzed 3 months after COVID-19. The majority of the children with asymptomatic/mild COVID-19 symptoms (80.6%), moderate/severe disease (90.9%), and MIS-C (82.4%) had detectable IgG antibodies to SARS-CoV-2 spike protein (p = 0.567). The mean antibody value against SARS-CoV-2 spike protein was 321.9 ± 411.6 in group 1, 274 ± 261 in group 2, and 220 ± 299 in group 3, respectively (p > 0.05). Patients diagnosed with COVID-19 (asymptomatic/mild+moderate/severe) and those with MIS-C were also compared; the antibody positivity rates [COVID-19 group: 85.5%, MIS-C group: 82.4%, (p = 0.833)] and mean antibody values [COVID-19 group: 303.9 ± 360.3, MIS-C group: 220 ± 299, (p > 0.05)] were similar in both groups. In conclusion, the majority of children with COVID-19 and MIS-C developed a detectable antibody level against SARS-CoV-2 spike protein 3 months after COVID-19. Quantitative antibody levels were similar in both asymptomatic/mild disease, moderate/severe disease, and MIS-C group. Long-term studies evaluating antibody responses in children with COVID-19 and MIS-C are needed for more accurate vaccine schedules.

Longitudinal survey of humoral and cellular response to SARS-CoV-2 infection in children

Background

Methods

Results

Conclusions

Antibody Responses to SARS-CoV-2 in Children With COVID-19

BACKGROUND

The immunologic features of children with coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are not clearly delineated. This study was conducted to evaluate SARS-CoV-2-specific antibody responses in children with COVID-19.

METHODS

The levels of anti-spike (S) IgG, anti-SARS-CoV-2 IgG, and neutralizing antibody (NAb) were measured during various time points in children <19 years of age with COVID-19 in South Korea from February 2020 to September 2020.

RESULTS

One hundred sixty-five blood samples from 114 children with COVID-19 (43.9% asymptomatic and 56.1% mildly symptomatic) were analyzed. In both asymptomatic and mildly symptomatic children, the positive rates of anti-S IgG, anti-SARS-CoV-2 IgG, and NAb were low within 7 days after onset, but they soon reached 100% 14 to <28 days after onset. In symptomatic children, the geometric mean titers (GMTs) of antibodies were all below the positive cutoff during the first 2 weeks from onset and peaked at 28 to <56 days (5.6 for anti-S IgG, 383.6 for anti-SARS-CoV-2 IgG, and 55.0 for NAb, P < .001, respectively). Antibody levels remained detectable up to 3 months after infection. The antibody GMTs during the period 14 to <56 days after symptom onset were highest in children aged 0-4 years.

CONCLUSIONS

These results collectively present the humoral immune responses during SARS-CoV-2 infection in children. A further longitudinal study is needed to thoroughly understand the immune system and for effective vaccine development in children during the COVID-19 pandemic.

Immunology of SARS-CoV-2 infection in children

Children and adolescents exhibit a broad range of clinical outcomes from SARS-CoV-2 infection, with the majority having minimal to mild symptoms. Additionally, some succumb to a severe hyperinflammatory post-infectious complication called multisystem inflammatory syndrome in children (MIS-C), predominantly affecting previously healthy individuals. Studies characterizing the immunological differences associated with these clinical outcomes have identified pathways important for host immunity to SARS-CoV-2 and innate modulators of disease severity. In this Review, we delineate the immunological mechanisms underlying the spectrum of pediatric immune response to SARS-CoV-2 infection in comparison with that of adults.

The antibody response to SARS-CoV-2 infection persists over at least 8 months in symptomatic patients

Background

Persistence of antibodies to SARS-CoV-2 viral infection may depend on several factors and may be related to the severity of disease or to the different symptoms.

Methods

We evaluated the antibody response to SARS-CoV-2 in personnel from 9 healthcare facilities and an international medical school and its association with individuals’ characteristics and COVID-19 symptoms in an observational cohort study. We enrolled 4735 subjects (corresponding to 80% of all personnel) for three time points over a period of 8–10 months. For each participant, we determined the rate of antibody increase or decrease over time in relation to 93 features analyzed in univariate and multivariate analyses through a machine learning approach.

Results

Here we show in individuals positive for IgG (≥12 AU/mL) at the beginning of the study an increase [p = 0.0002] in antibody response in paucisymptomatic or symptomatic subjects, particularly with loss of taste or smell (anosmia/dysgeusia: OR 2.75, 95% CI 1.753 – 4.301), in a multivariate logistic regression analysis in the first three months. The antibody response persists for at least 8–10 months.

Conclusions

SARS-CoV-2 infection induces a long lasting antibody response that increases in the first months, particularly in individuals with anosmia/dysgeusia. This may be linked to the lingering of SARS-CoV-2 in the olfactory bulb.

Levi and Ubaldi et al. evaluate SARS-CoV-2 seroprevalence in a cohort of 4735 healthcare workers in northern Italy. In seropositive individuals, they show that antibodies are maintained over a period of 8 to 10 months and associate changes in antibody levels over this period with symptoms and specific subgroups of participants.

SARS-CoV-2 infection activates the body’s immune system to fight off infection. This immune response results in the production of proteins in the blood that target the virus called antibodies. The extent and duration of this antibody response may be associated with the type of symptoms the infected person is experiencing. Here, we analyzed SARS-CoV-2 antibody levels in individuals with asymptomatic, mild symptomatic (paucisymptomatic) and symptomatic disease in relation to the type of symptoms. We find that the antibody response is higher in people with symptoms and increases in the first three months, particularly in individuals with loss of smell or taste. In all people with SARS-CoV-2 antibodies at the start of the study, levels in the blood last for at least 8–10 months. Hence, SARS-CoV-2 infection is characterized by a long lasting antibody response which may protect from subsequent infections.