ABSTRACT
Objectives@#The aim of this study was to assess changes in the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunoglobulin G (IgG) seroprevalence among children and adolescents in Delhi, India from January 2021 to October 2021 @*Methods@#This was a repeated cross-sectional analysis of participants aged 5 to 17 years from 2 SARS-CoV-2 seroprevalence surveys conducted in Delhi, India during January 2021 and September to October 2021. Anti-SARS-CoV-2 IgG antibodies were detected by using the VITROS assay (90% sensitivity, 100% specificity). @*Results@#The seroprevalence among 5- to 17-year-old school-age children and adolescents increased from 52.8% (95% confidence interval [CI], 51.3%−54.3%) in January 2021 to 81.8% (95% CI, 80.9%−82.6%) in September to October 2021. The assay-adjusted seroprevalence was 90.8% (95% CI, 89.8%−91.7%). Seropositivity positively correlated with participants’ age (p<0.001), but not sex (p=0.388). A signal to cut-off ratio ≥4.00, correlating with the presence of neutralization antibodies, was observed in 4,814 (57.9%) participants. @*Conclusion@#The high percentage of seroconversion among children and adolescents indicates the presence of natural infection-induced immunity from past exposure to the SARS-CoV-2 virus. However, the lack of hybrid immunity and the concomitant likelihood of lower levels of neutralization antibodies than in adults due to the absence of vaccination warrants careful monitoring and surveillance of infection risk and disease severity from newer and emergent variants.
ABSTRACT
BackgroundWe conducted a repeat serosurvey in Delhi, India to estimate the seroprevalence of SARS-CoV-2 in the general population and compare the antibody prevalence in the vaccinated and non-vaccinated groups. MethodsThis cross-sectional study was conducted from September 24 to October 14 2021 in 280 wards of Delhi among 27811 participants selected through a multistage sampling technique with housing settlement based stratification. The SARS-CoV-2 immunoglobulin (IgG) antibodies were screened with the VITROS(R) (Ortho Clinical Diagnostics, Raritan, NJ, USA) assay (90% sensitivity, 100% specificity). ResultsA total of 24895 (89.5%) samples were seropositive. The crude seroprevalence was 87.99% (95% CI 89.1, 89.8), weighted for age and sex was 88% (95% CI 87.6, 88.4), and after adjustment of assay performance was estimated as 97.5% (95% CI 97.0, 98.0). The weighted seroprevalence in the 11 districts ranged from 84.9% (South-West district) to 90.8% (East district) Females in all the age-groups (<18, 18-49 and [≥]50) had significantly higher odds of seropositivity (p<0.001). On adjusted analysis, the odds of seroconversion in the participants vaccinated with at-least one dose of either Covid-19 vaccine (Covishield/Covaxin) was more than four times compared to the unvaccinated (aRR 4.2 (3.8, 4.6)). The seroprevalence was also comparable among the complete and partially vaccinated subgroups for both vaccines (Table 4). Most (86.8%) seropositive individuals had a SARS-CoV-2 signal/cut-off [≥]4.0 except in children O_TBL View this table: org.highwire.dtl.DTLVardef@1482d5forg.highwire.dtl.DTLVardef@19ab8a1org.highwire.dtl.DTLVardef@cf675dorg.highwire.dtl.DTLVardef@8b427aorg.highwire.dtl.DTLVardef@b96a54_HPS_FORMAT_FIGEXP M_TBL O_FLOATNOTable 4.C_FLOATNO O_TABLECAPTIONVaccination status and seroprevalence of antibodies to SARS-CoV-2, Delhi, September-October 2021* C_TABLECAPTION C_TBL ConclusionsWe observed IgG antibodies against SARS-CoV-2 in most of the general population of Delhi with likely higher antibody titres in the vaccinated compared to the unvaccinated groups.
ABSTRACT
We conducted this study to estimate seroprevalence of neutralizing antibodies in the general population and to further correlate it with the IgG SARS-CoV-2 IgG levels. This present cross-sectional analysis was conducted as a sequel to a state level community-based seroepidemiological study in Delhi, India. A total of 2564 seropositive samples were selected from 25622 seropositive samples through simple random sampling. Neutralizing capacity was estimated by performing a surrogate virus neutralization test with the sVNT (GenScript) assay. Neutralizing antibody against the SARS-CoV-2 virus was operationally considered as detected when the signal inhibition was [≥]30%. A total of 2233 (87.1%, 95% C.I. 85.7, 88.3) of the 2564 SARS-CoV-2 seropositive samples had detectable neutralizing antibodies. On bi-variate analysis but not on adjusted analysis, Covid-19 vaccination showed a statistically significant association with the presence of neutralizing antibodies (p<0.001). The signal/ cut off (S/CO) of SARS-CoV-2 IgG ranged from 1.00 to 22.8 (median 11.40). In samples with S/CO [≥]4.00, the neutralizing antibodies ranged from 94.5 to 100%, while in samples with S/CO <4.00, it ranged from 52.0 to 79.2%. The neutralizing antibody seroprevalence strongly correlated with the S/CO range (r=0.62, p=0.002). In conclusion, in populations with high SARS-CoV-2 seroprevalence, neutralizing antibodies are generated in nearly 9 of 10 seropositive individuals.
ABSTRACT
IntroductionThe study objective was to determine the breakthrough infection rate of Covid-19 (SARS-CoV-2) infection in those vaccinated with either BBV152 or AZD1222 (ChAdOx1-S) vaccine among healthcare workers (HCWs). MethodsA cross-sectional analysis was conducted a medical college and hospital complex in Delhi, India through telephonic interviews among HCWs who had received at-least one dose of a Covid-19 vaccine during January to March 2021. Breakthrough infections were operationally defined as occurrence of Covid-19 infection [≥]14 days after administration of two doses of either Covid-19 vaccine. ResultsWe enrolled 325 HCWs with mean (SD) age of 29.1 (9.9) years including 211 (64.9%) males. Two seventy nine (85.8%) HCWs were fully vaccinated while 46 (14.2%) were partially vaccinated. There were 168 (51.7%) BBV152 and 157 (48.3%) AZD1222 (ChAdOx1-S) recipients. A total of 37 (11.3%, 95% C.I. 8.3, 15.3) breakthrough infections were observed in the HCWs. The median (IQR) time until incidence of Covid-19 breakthrough infection since receiving second dose of either Covid-19 vaccine was 47 (28.5, 55) days. Additionally, 20 (6.1%) non-breakthrough Covid-19 infections were recorded in the HCWs post vaccination with either a single dose of a Covid-19 vaccine or both doses but prior to a period of 14 days since administration of the second dose. Most breakthrough infection cases (94.4%) were mild and did not require supplemental oxygen therapy. HCWs without a history of natural Covid-19 infection and recovery prior to vaccination were 3.8 times more at risk to contract a Covid-19 infection or reinfection in spite of vaccination with at-least one dose of either Covid-19 vaccine. ConclusionNearly one in nine HCWs experienced a Covid-19 breakthrough infection in the present study.
