Seroprevalence of SARS-CoV-2 Infection in the Colombo Municipality Region, Sri Lanka

Abstract

Background: As the Municipality Council area in Colombo (CMC) experienced the highest number of cases until the end of January 2021, in Sri Lanka, we carried out a serosurvey prior to initiation of the vaccination program to understand the extent of the SARS-CoV-2 outbreak.Methods: SARS-CoV-2 seropositivity was determined in 2,547 individuals between the ages of 10–86 years, by the Wantai total antibody ELISA. We also compared seroprevalence using the haemagglutination test (HAT) to evaluate its usefulness in carrying out serosurveys.Results: The overall seropositivity rate was 24.46%, while seropositivity by HAT was 18.90%. Although The SARS-CoV-2 infection detection rates by PCR were highest in the population between the ages of 20–60 years of age, there was no statistically significant difference in the seropositivity rates in different age groups. For instance, although the seropositivity rate was highest in the 10–20 age group (34.03%), the PCR positivity rate was 9.80%. Differences in the PCR positivity rates and seropositivity rates were also seen in 60–70-year-olds (8.90 vs. 30.4%) and in individuals >70 years (4.10 vs. 1.20%). The seropositivity rate of the females was 29.70% (290/976), which was significantly higher (p < 0.002) than in males 21.2% (333/1,571).Conclusions: A high seroprevalence rate (24.5%) was seen in all age groups in the CMC suggesting that a high level of transmission was seen during this time. The higher PCR positivity rates between the ages of 20–60 are likely to be due to increased testing carried out in the working population. Therefore, the PCR positivity rates, appear to underestimate the true extent of the outbreak and the age groups which were infected.

Sensitivity and specificity of two WHO approved SARS-CoV2 antigen assays in detecting patients with SARS-CoV2 infection

“…The Wantai ELISA assay was shown to have a sensitivity of 98% [ 11 ]. It was also found to be 100% specific when tested in over 100 serum samples obtained in year 2018, in Sri Lankan individuals [ 12 ]. The assay was carried out and results were interpreted according to manufacturers’ instructions.…”

The magnitude and cross reactivity of SARS-CoV-2 specific antibody responses in vaccinated and unvaccinated Sri Lankan children and association with nutrition status

“…The HAT was carried out as previously described using the BA.2.75 and XBB.1.5 versions of the IH4-RBD reagents with additional mutations in the RBD (Y365F, T392W and V395I) [22, 23]. The assays were carried out and interpreted as previously described by us and these assays have been used previously in serosurveys carried out in the Colombo district in Sri Lanka [16, 24]. The HAT assays were performed with sera at 1:40 and 1:80 dilutions, to determine presence of RBD-specific antibodies.…”

“…SARS-COV-2 specific total antibody (IgM, IgG and IgA) responses were evaluated using the Wantai SARS-CoV-2 Ab ELISA (Beijing Wantai Biological Pharmacy Enterprise, China) as previously described. This assay has been used in carrying out serosurveys for SARS-CoV-2 previously in Sri Lanka, in the Colombo district [16]. This assay was shown to have a sensitivity of 98% [17] and was found to be 100% specific in serum samples obtained in 2018, in Sri Lankan individuals.…”

Severe Acute Respiratory Syndrome Coronavirus 2 Infections in Children

“…These studies show that SARS-CoV-2 infections in children have been frequently underdiagnosed. 12 , 13 , 14 Many of these studies conducted in different countries before 15 , 16 , 17 , 18 and after vaccine availability 19 showed a lower number of infection-derived SARS-CoV-2 antibody detection in children compared to adults. However, country and regional study differences conducted at varying timepoints during the pandemic have reported mixed results.…”