Douglas Wixted

Background: Surveillance estimates of SARS-CoV-2 infections over time have relied on mandatory clinician and laboratory reporting. These estimates increasingly underestimated true viral incidence due to asymptomatic infections, variable access to testing, and self-administered diagnostics. To overcome these limitations, the North Carolina Department of Health and Human Services partnered with academic researchers to conduct three concurrent population-based longitudinal cohort studies in three distinct North Carolina counties to offer more accurate estimates of the incidence, prevalence, and vaccination rates for SARS-CoV-2. Methods: We enrolled and followed adult residents of three North Carolina counties from August 2020-February 2022. Demographic and health information was collected in biweekly surveys. Nasal swabs were collected biweekly and tested for SARS-CoV-2 using PCR testing. Blood samples were collected monthly and tested for antibodies to the SARS-CoV-2 nucleocapsid and spike proteins. We calculated monthly seroprevalence, sero-incidence, PCR test positivity, and vaccination uptake. Results: We enrolled 646 participants. Routine blood samples and nasal swab samples were contributed by 639 and 642 participants, respectively. By February 2022, 98% (95% CI: 97.4–98.2) had antibodies to the SARS-CoV-2 spike protein, and 13% (95% CI: 12.4–14.2) had antibodies to the nucleocapsid protein, indicating viral exposure. PCR testing detected infection among 14% (95% CI: 13.1–15.0) of participants, but cumulative PCR test positivity was only 1.3% (95% CI: 1.2–1.4). Over half of PCR-detected infections were asymptomatic. By February 2022, 97% of participants had completed the primary vaccine series, and 52% had received a booster dose. Conclusions: Nearly all participants had anti-SARS-CoV-2 antibodies by the end of follow-up, primarily through vaccination. The incidence of PCR-detected infections was similar to antibody testing, but PCR test positivity substantially underestimated incident infections. These findings emphasize the importance of prospective infection monitoring via antibody testing in a comprehensive approach to tracking viral infections in the community setting.

Many studies identified factors associated with vaccination intention and hesitancy, but factors associated with vaccination promptness and the effect of vaccination intention on vaccination promptness are unknown. This study identified factors associated with COVID-19 vaccination promptness and evaluated the role of vaccination intention on vaccination promptness in 1223 participants in a community-based longitudinal cohort study (June 2020 to December 2021). Participants answered questions regarding COVID-19 vaccination intention, vaccination status, and reasons for not receiving a vaccine. The association of baseline vaccine hesitancy with vaccination was assessed by the Kaplan–Meier survival analysis. Follow-up analyses tested the importance of other variables predicting vaccination using the Cox proportional hazards model. Older age was associated with shorter time to vaccination (HR = 1.76 [1.37–2.25] 85-year-old versus 65-year-old). Lower education levels (HR = 0.80 [0.69–0.92]), household incomes (HR = 0.84 [0.72–0.98]), and baseline vaccination intention of ‘No’ (HR = 0.16 [0.11–0.23]) were associated with longer times to vaccination. The most common reasons for not being vaccinated (N = 58) were vaccine safety concerns (n = 33), side effects (n = 28), and vaccine effectiveness (n = 25). Vaccination campaigns that target populations prone to hesitancy and address vaccine safety and effectiveness could be helpful in future vaccination rollouts.

Background: Mitigation behaviors reduce the incidence of COVID-19 infection. Determining characteristics of groups defined by mitigation behaviors compliance may be useful to inform targeted public health policies and interventions. This study aimed to identify groups of individuals according to self-reported compliance with COVID-19 mitigation behaviors, define compliance class characteristics, and explore associations between compliance classes and important study and public health outcomes. Methods and findings: We studied 1,410 participants in the Cabarrus County COVID-19 Prevalence and Immunity longitudinal cohort study (June 2020 to December 2021) who were asked 10 questions regarding compliance with recommended COVID-19 mitigation behaviors. By Latent Class Analysis, 1,381 participants were categorized into 3 classes (most [49.4%], moderately [45.0%], and least [5.6%] compliant). Compared with the most compliant class, the least and moderately compliant classes were younger (mean = 61.9 v. 59.0 v. 53.8 years), had fewer medical conditions per individual (1.37 v. 1.08 v. 0.77), and differed in Hispanic ethnicity (6.2% v. 2.8% v. 9.1%) and COVID-19 vaccine intention (65.8% v. 59.8% v. 35.1%). Compared to the most compliant class, the least compliant class had fewer women (54.6% v. 76.3%), fewer insured individuals (92.2% v. 97.4%), and more withdrew from study participation early (28.6% v. 16.0%). Relative to the most compliant class, the least compliant class had a higher likelihood of COVID-19 infection (OR = 2.08 [95% CI 1.13, 3.85]), lower rate of COVID-19 vaccination (72.6% v. 95.1%), and longer time to 50% COVID-19 vaccination following eligibility (8–9 vs 16 days). Conclusions: Classes defined by mitigation behaviors compliance had distinct characteristics, including age, sex, medical history, and ethnicity, and were associated with important study and public health outcomes. Targeted public health policies and interventions according to the compliance group characteristics may be of value in current and future pandemic responses to increase compliance.

The Coronavirus Disease 2019 (COVID-19) pandemic forced researchers to reconsider in-person assessments due to transmission risk. We conducted a pilot study to evaluate the feasibility of using the Tasso-SST (Tasso, Inc, Seattle, Washington) device for blood self-collection for use in SARS-CoV-2 antibody testing in an ongoing COVID-19 prevalence and immunity research study. 100 participants were recruited between January and March 2021 from a previously identified sub-cohort of the Cabarrus County COVID-19 Prevalence and Immunity (C3PI) Study who were under-going bimonthly COVID-19 antibody testing. Participants were given a Tasso-SST kit and asked to self-collect blood during a scheduled visit where trained laboratory personnel performed routine phlebotomy. All participants completed an after-visit survey about their experience. Overall, 70.0% of participants were able to collect an adequate sample for testing using the device. Among those with an adequate sample, there was a high concordance in results between the Tasso-SST and phlebotomy blood collection methods (Cohen’s kappa coefficient = 0.88, Interclass correlation coefficient 0.98 [0.97, 0.99], p < 0.0001). The device received a high-level (90.0%) of acceptance among all participants. Overall, the Tasso-SST could prove to be a valuable tool for seroprevalence testing. However, future studies in larger, diverse populations over longer periods may provide a better understanding of device usability and acceptance among older participants and those with comorbidities in various use scenarios.