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SARS-CoV-2 Seroprevalence and Symptom Onset in Culturally Linked Orthodox Jewish Communities Across Multiple Regions in the United States

Our take —

This cross-sectional study examined the seroprevalence and symptom onset of SARS-CoV-2 infection among Orthodox Jewish communities in 5 US states. They found high prevalence of reported symptoms (61.0%) and high seroprevalence overall (30.1%) using antibody testing. Symptom onset was most frequent in March 2020, generally between March 9 and 31. The study’s primary limitation was the use of antibody testing which only reflects ever having been infected, and not whether onset of presumed COVID-19 symptoms actually corresponded to SARS-CoV-2 infection. Therefore, these estimates may not accurately reflect incident disease over the entire study period, but rather history of an illness and a SARS-CoV-2 infection. Further, estimates may under or overrepresent individuals based on infection severity or presumption, or community sub-group and thus should be interpreted with these caveats.

Study design

Cross Sectional

Study population and setting

The objective of this cross-sectional study was to understand the signs and symptoms, and seroprevalence, of SARS-CoV-2 in a cultural community with reported high rates of infection across 5 states in the US: New York, New Jersey, Connecticut, California, and Michigan. Participants were recruited in partnership with local non-profit and social service organizations serving Orthodox Jewish people 18 years and older. In the first stage of recruitment, which aimed to determine self-reported symptoms and infection, 12,626 individuals began the survey, 9,507 completed the it (75.3% completion) and 603 had obtained a positive PCR test (6.6%) during their illness. In the second stage of recruitment, a subset totaling 6,665 adults (70.1% response rate) had antibody testing following survey completion. Of the 6,665 in the antibody cohort, 422 (6.4%) obtained a positive PCR test during their illness and 2004 (30.1%) had a positive antibody test at the time of the study. The survey included patient demographics, symptoms of COVID-19, date of symptom onset, and whether they had been tested for SARS-CoV-2 by nasal swab.

Summary of Main Findings

In the full survey cohort, 61.0% (N=5803) of people in the survey cohort reported symptoms at any point in the study. The earliest date of symptom onset with a positive nasal swab test was on February 8, 2020 in Michigan. The median and mode dates of symptom onset occurred within the same 1-week period from March 13 to 20 across all sites. In the antibody cohort (N=6,665 individuals), 2004 individuals tested positive via antibody test (30.1%). The highest seroprevalence was in New Jersey (32.5%, N=1080), followed by New York (30.5%, N=671). As in the full cohort, most individuals within the antibody cohort reported symptom onset between March 9 and March 31, though the earliest reported date with an eventual positive antibody test was in New Jersey on December 18, 2019.

Study Strengths

The study’s main strength was the large number of Orthodox Jewish people who participated in the study, allowing the researchers to examine geographic differences and describe the temporal trends in symptom onset across multiple states. They additionally noted that the date of median and mode onset were approximately 7 to 10 days following a major Jewish festival (Purim) across all sites. They also were able to accurately describe prior infection using seroprevalence measures with their antibody testing.


The primary limitation was that the researchers only had cross-sectional data available to them reflecting ever-infection through antibody testing, and then self-reported symptoms. For instance, for individuals reporting very early symptom onset in December and January, it was not possible to determine if this was SARS-CoV-2 infection or an unrelated respiratory illness and they later became infected with SARS-CoV-2 which was then captured by the antibody test. Additionally, the study only included cases of disease where participants could participate in the community, as opposed to hospital-based data collection. Therefore, it may not have reflected cases of severe disease. There also may have been volunteer bias, with individuals suspecting they had SARS-CoV-2 being more likely to participate than others, which would inflate their estimate of seroprevalence. Additionally, the population was largely Ashkenazi Jewish with limited racial diversity, thereby reflecting primarily white Orthodox Jewish people and not Orthodox Jewish people of color.

Value added

The study is the largest to date of a tight-knit religious and cultural community that experienced high prevalence of COVID-19 during the pandemic.

This review was posted on: 5 April 2021