Effectiveness of Interventions for Controlling COVID-19 Transmission between Construction Workers and Their Close Contacts

The insufficiency of continued nonpharmaceutical interventions (NPIs) and ongoing vaccination programs continues to pose
challenges in recovering from the COVID-19 pandemic. Before herd immunity, controlling at-risk and vulnerable groups in combination
with vaccination plans is strongly recommended. The construction industry is especially vulnerable to the negative impacts of COVID-19 as
illustrated by frequent relevant clusters globally and given the manual labor performed by construction workers in close physical proximity,
which increases the likelihood of exposure. To gain insights into the transmission dynamics of COVID-19 to inform the establishment
of effective and targeted NPIs in the construction industry, a dual-community model was developed that includes the susceptible–exposed–
infectious/asymptomatic–hospitalized–recovered–pathogen (SEI/AHR-P) model for construction workers and the susceptible–exposed–
infectious/asymptomatic–hospitalized–recovered (SEI/AHR) model for their close contacts. The results of our sensitivity analysis corroborate
previous findings that close contacts are significant participants in the spread of the infection. However, the contributions of indirect transmission pathways at a construction site were found to be weak, suggesting the need for further study given conflicting results in other
research. Based on the parameters identified as significant in the sensitivity analyses, 28 NPI scenarios were devised to analyze the total
attack rate (TAR) and duration of an outbreak (DO). The scenario in which exposed individuals are controlled in terms of close contacts
performs best, reducing the TAR with 25% absolute efficiency (AE) and decreasing the DO in the whole population by 1.8 days. In addition
to NPIs, both construction workers and their close contacts are suggested to get vaccinated. Vaccination of all construction workers would
lead to a lower TAR compared to vaccination of only 15% of both construction workers and their close contacts. Vaccination of all construction workers along with at least 67% of their close contacts can extinguish an ongoing wave.