The coronavirus disease 2019 (COVID-19) pandemic has made it necessary to prioritize decision-making on crucial measures, such as contact tracing, testing, and vaccination. In the US, there is significant heterogeneity with respect to these mitigating measures.

Younger individuals, racial and ethnic minorities, individuals with lower socioeconomic statuses, and certain occupational groups all show lower uptakes. Many studies have focused on risk factors associated with severe COVID-19 disease, but there is a lack of research on assessing relative population risks regarding the acquisition of the disease.

A new study has been posted on the medRxiv* preprint server that analyzes risk factors for acquiring COVID-19 in a large, prospective cohort of adult residents in the Boston metropolitan area.

Background

Researchers have been able to compare confirmed COVID-19 incidence by geography, age, and racial/ethnic groups, by means of polymerase chain reaction (PCR) test results. However, inference related to the risk of different populations acquiring infection is difficult, owing to variable access to testing, during the pandemic.

Further, close to half of the COVID-19 cases are asymptomatic, thereby not prompting PCR testing. Local and national testing trends are also difficult to estimate owing to a lack of granularity of testing details, e.g., employment status, household composition, and medical comorbidities.

Unbiased seroprevalence monitoring could help in obtaining better estimates of the proportion of individuals who had not yet been exposed to infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and those not yet vaccinated. This group could be assumed to be at the greatest risk of infection. To inform risk mitigation measures, researchers of the current study examined the risks associated with the incidence of SARS-CoV-2 infection in a cohort of adults in a major US metropolitan area.

A new study

A cohort of 150,000 adults who lived within a 45-mile radius of Boston were eligible to enroll in the Test Boston Study and they were presented with the option of participating in a longitudinal panel with a follow-up at six months. The cohort was demographically representative of the general population of Massachusetts based on age, gender, and race/ethnicity.

Baseline surveys and follow-up questionnaires were completed by participants. The follow-ups were aimed at gathering additional information on new COVID-like symptoms, testing, and history of any vaccination that occurred in the prior 30 days. Self-collection test kits were shipped directly to the participant’s home. The sample size was determined to enable researchers to estimate an overall seroprevalence of COVID–19 infection of 5% or higher. It also aided in the estimation of the seroprevalence of COVID–19 infection by age groups, gender, and ethnicity with high accuracy.

Main results

Researchers stated that between October 2020 and January 2021, they enrolled 10,289 adults, and the characteristics of the sample were reflective of Massachusetts census data. 567 individuals, or 5.5% of participants, presented evidence of current or prior SARS-CoV-2 infection. By June 15, 2021, this number increased to 13.4%. Scientists were able to document some racial heterogeneities as well. Black non-Hispanic participants had a 2.2 fold greater risk of acquiring COVID-19, compared to white participants. In the case of Hispanic participants, the risk was 1.5 fold greater, compared to their white counterparts.

Younger adults (18-29 years of age), those who lived with other adults, and children, and those who worked outside their homes, were perceived to be at an elevated risk of acquiring COVID-19. Socioeconomic status was also observed to play an important role. Individuals in the second and third lowest disadvantaged neighborhood communities were associated with a higher risk of SARS-CoV-2 infection. Surprisingly, individuals with medical risk factors for severe COVID-19 disease were observed to be at a reduced risk of SARS-CoV-2 acquisition.

Concluding remarks

The results documented in this study show that socioeconomic status and race/ethnicity are not the only risk factors for the severity of COVID-19 disease, but are also the biggest determinants of acquisition of SARS-CoV-2 infection. Scientists stated that this disparity is significantly underestimated if based on PCR data alone. This was clearly demonstrated by the discrepancy in serology vs. PCR detection for non-white study participants.

Surprisingly, comorbidities and older age were associated with a lower risk of acquisition of COVID-19, despite being the factors that increase the risk of severe disease. This finding suggests the importance of behavior modifications that individuals might be undertaking.

Taken together, the findings highlight the need for risk mitigation programs aimed at overcoming the challenges of structural racism, which should help in better management of the current and future pandemics.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Dr. Priyom Bose

Priyom holds a Ph.D. in Plant Biology and Biotechnology from the University of Madras, India. She is an active researcher and an experienced science writer. Priyom has also co-authored several original research articles that have been published in reputed peer-reviewed journals. She is also an avid reader and an amateur photographer.