About these surveys
CDC is working with industrial laboratories to conduct large-scale geographic seroprevalence surveys to estimate the share of people that have been beforehand contaminated with SARS-CoV-2, the virus that causes COVID-19 illness. The technique entails working with state, native, territorial, educational, and industrial companions to raised perceive COVID-19 in the US utilizing serology (antibody) testing for surveillance (“seroprevalence surveys” or “serosurveys”). For the surveys, de-identified scientific blood samples are examined for antibodies to SARS-CoV-2.
Preliminary Ten-Web site Industrial Laboratory Seroprevalence Survey
The industrial laboratory seroprevalence survey used blood samples collected from 10 US websites throughout March to July 2020. These websites have been Connecticut, Louisiana, Minnesota, Missouri, New York Metropolis, Philadelphia, San Francisco, South Florida, Utah, and Western Washington State. The survey included blood specimens examined for causes unrelated to COVID-19, resembling for routine medical care or a sick go to. CDC examined about 1,800 samples collected from every of those 10 websites, roughly each 3–4 weeks.
Nationwide Industrial Laboratory Seroprevalence Survey
In July 2020, CDC expanded the seroprevalence survey to incorporate industrial laboratories throughout 50 US states, Washington, DC, and Puerto Rico. The survey makes use of blood samples submitted to industrial laboratories for causes unrelated to COVID-19, resembling routine medical care or a sick go to.
This survey goals to gather 50,000 blood samples each 2 weeks for a complete of greater than 1.2 million samples till August 2021. Seroprevalence estimates for each sexes and particular age teams may not be out there for some websites as a result of too few blood samples have been collected. The outcomes of the nationwide survey can’t be in contrast straight with outcomes from the preliminary 10-site industrial laboratory seroprevalence survey as a result of the laboratories from which samples have been collected are totally different, the SARS-CoV-2 serology assessments utilized in every research differ, and the geographic distribution of the 2 research populations modified. Researchers are investigating what proportion of blood specimens examined have antibodies in opposition to SARS-CoV-2, how this varies throughout geographic areas and age teams, and whether or not the share of SARS-CoV-2 infections has modified over time in the course of the survey.
Weighted seroprevalence estimates with 95% confidence intervals are calculated for every website each 2 weeks. Seroprevalence estimates are adjusted (weighted) to match age and intercourse distribution to the pattern inhabitants inside every website after which standardized to the age and intercourse distribution obtained from the American Group Surveyexterior icon inhabitants information for every website. This method accounts for a number of sources of variability together with biases in pattern assortment, the demographics of every website, and accuracy of various serology assessments (i.e., sensitivity and specificity). This variability is reported as 95% confidence intervals.