Mobile COVID-19 testing program in Phoenix: A retrospective ... : Medicine (original) (raw)

1. Introduction

Three years have passed since the onset of the coronavirus (COVID-19), and COVID-19 remains a global public health challenge. To date, there has been over 760 million cases and over 6.9 million deaths worldwide, with over one million deaths across in the United States alone.[1,2] In Arizona, with a population of 7.2 million, there has been over 2.5 million cases of COVID-19.[3]

During the start of the pandemic, the State of Arizona utilized various different mitigation techniques in attempts to control the spread of COVID-19. On March 11, 2020, a state of emergency was declared, and several executive orders were signed to limit crowds and gatherings. Restrictions were placed to limit capacity at restaurants and gyms, and social distancing and mask mandates were implemented.[4] While these measures proved beneficial and effective in controlling the initial surge of COVID-19 cases, as case counts started to decline, another executive order was signed in May 2020, to slowly begin reopening businesses.[5] In July 2020, some school districts resumed in-person classes.[6,7] As the State began to reopen, cases again started to climb, and by the end of the calendar year 2020, Arizona became a hotspot with 118.3 new cases per 100,000 people.[3] During this time, in December 2020, COVID-19 vaccines began to be available, offering another line of protection to individuals. As more individuals began to be fully vaccinated, social restrictions continued to relax. In May 2021, the Centers for Disease Control and Prevention (CDC) recommendations changed, allowing fully vaccinated individuals to forgo social distancing and mask use in many public settings.[8] As of June 12, 2022, the CDC recommendations for international air travel changed, and individuals, boarding a flight to the United States, regardless of vaccination status, no longer required a negative COVID-19 testing or documentation of recovering from a recent COVID-19 infection.[9]

With the continued cycles of COVID-19 cases, there must be plans and mitigation techniques in place to keep businesses and schools open. To ensure these plans and techniques are based on scientific data and evidence, we must analyze the past trends in COVID-19 cases and positivity rates.

This current study analyzes COVID-19 antigen positivity rates between December 2020 and April 2022 from a mobile testing program in the Phoenix metropolitan area. The rationale for this study is to improve our understanding of the trends in COVID-19 cases and positivity rates in the Phoenix metropolitan area and how it compares to Arizona. This data can then be used to guide public health planning and mitigation techniques to ensure businesses and schools remain open while keeping citizens safe. This knowledge can also be extrapolated to future pandemics and global public health crises.

2. Methods

A retrospective analysis of Vincere mobile COVID-19 testing in the Phoenix Metropolitan Area compared to Arizona State from December 2020 and April 2022 was performed. Inclusion criteria included positive and negative COVID-19 test counts from Vincere and Arizona State. These numbers were abstracted from data reported to the Arizona Department of Health Services (ADHS). There were no exclusion criteria.

Since this is a retrospective study of de-identified data (with no patient identifying information), including data that was made publicly available by the ADHS, this study did not require review by an institutional review board.

2.1. Vincere mobile COVID-19 testing program

During this time, Vincere partnered with the City of Phoenix to provide mobile COVID-19 testing throughout the Phoenix Metropolitan Area, with an emphasis on underserved areas. COVID-19 antigen testing was available for all individuals age 3 years and older. Testing was available up to 6 days a week, including evening and weekend hours, and individuals had the option of scheduling appointments in advance or walk-up visits. Insurance was not required, and testing was available to all individuals free of charge. During this public health emergency, any facility conducting COVID-19 testing was required to report test results (number of positive and negative tests) to the Arizona State Department of Health within 24 hours of test completion. Case counts were made publicly available on the ADHS website and daily news media updates.

2.2. COVID-19 testing

Vincere mobile COVID-19 testing was performed using the Quidel SOFIA SARS Antigen Fluorescent Immunoassay. This test utilizes an immunofluorescence-based lateral flow technology to qualitatively detect the nucleocapsid protein from SARS-CoV-2. This test received Food and Drug Administration, Emergency Use Authorization (sensitivity: 100%, specificity: 98.8%, positive predictive accuracy: 96.7%, negative predictive accuracy: 100%).[10] Nasal or nasopharyngeal swabs were collected from patients, processed on-site, and results given to the patient within 15 minutes. All tests were performed and interpreted by trained healthcare professionals, including emergency medical technicians/paramedics, medical assistants, registered nurses, physician assistants, and physicians.

2.3. Outcome

2.3.1. Primary outcome.

COVID-19 antigen positivity rate.

2.4. Statistical analysis

Daily aggregate total positive and negative COVID-19 antigen testing results from December 1, 2020 to April 16, 2022 was extracted, as reported to the ADHS. Weekly total case counts and positivity rates were calculated. Trends in COVID-19 case counts and positivity rates between Vincere and Arizona State were compared.

2.4.1. Data availability.

The datasets generated during and/or analyzed during the study are available from the corresponding author on reasonable request. Data counts can be publically accessed from the ADHS.[3]

3. Results

During this timeframe, a total of 72,827 COVID-19 antigen tests were performed with a total of 8666 positive tests (11.9% positivity rate). There was an increase in the number of tests between December 2020 to February 2021, and December 2021 to February 2022. Peak positivity rates were seen in January 2021 (13.96%) and January 2022 (24.84%). A small increase in the number of tests performed was also seen between August 2021 and September 2021, peaking at 11.16% at the end of August 2021. Trends in the number of COVID-19 tests performed and positivity rates are shown in Figure 1. The bar graphs indicate the number of positive COVID-19 cases (as measured by the number of positive COVID-19 tests) [blue], as a fraction of the total number of COVID-19 tests performed [orange]. The line graphs represent positivity rates. Vincere positivity rate is shown in red. Arizona State positivity rate is shown in gray.

Figure 1.:

COVID-19 cases and positivity rate of Vincere and Arizona State.

As shown, the number of COVID-19 cases (as identified as positive COVID-19 tests) from Vincere mobile testing site mirrors the ADHS data. Similar rises in COVID-19 positivity rates were seen during the fall and winter months were seen, resulting in peak positivity rates in January and February.

4. Discussion

Three years since the onset, COVID-19 remains an ongoing global public health challenge. While the world recovers from this pandemic, it is crucial to review the response to the current pandemic to plan for future pandemics and global public health crises. This retrospective study analyzes the trends and emerging patterns in COVID-19 testing and antigen positivity rates from a mobile COVID-19 testing program in the Phoenix metropolitan area, the largest city in Arizona, between December 2020 and April 2022.

There was a large increase in COVID-19 testing and positivity rates between December 2020 to February 2021 and December 2021 to February 2022. These surges and peaks mirror the ADHS data and is likely attributed to the increase in social gatherings and travel during the holiday season.[2,10–12] Close-contact environments, such as family and social gatherings, are associated with higher rates of COVID-19 transmission, with reports as high as 18.7 times higher odds of COVID-19 transmission compared to open-air environments (OR 18.7; 95% CI, 6.0–57.9).[13–16] Increased air travel, longer wait times and flight delays during the holiday season further increase risk of transmission through close contact environments. It is estimated that 1 million to 2 million people traveled each day throughout the holiday seasons, with these values peaking at the end of December and early January.[17] Many previous studies have reported that increased human mobility via air, rail, and public transit have contributed to the spread of the COVID-19 pandemic.[18–20] The decline in numbers following the holidays further support the impact of social gatherings during the holidays in COVID-19 transmission.

A slight increase in COVID-19 testing and positivity rates over baseline was also noted between August 2021 to September 2021. This is likely attributed to the start of the new school year, which typically open the first week of August in Arizona. Although masks were recommended, there were no mask mandates in most school districts.

Another significant observation from our study is the larger waves in 2021 to 2022 compared to 2020 to 2021. Various factors may have been responsible for this observation. The degree of masking was significantly lower, since the mask mandate was removed earlier in July 2021.[8] Restrictions regarding social gatherings were also relaxed, compared to the start of the pandemic. Though many schools started in-person learning later in the 2020 school year, some waited until the start of the 2021 to 2022 school year. Relaxation of social distancing norms, removal of mask mandate and return to “normalcy” likely led to increased social interactions in close proximity. Pandemic fatigue is another important factor to consider. Furthermore, with the availability of vaccines and antiviral medications, an individual’s risk tolerance changes.

Baseline positivity rates at our mobile testing site appear slightly higher than Arizona State rates, which may be attributed to the program’s focus on underserved populations. These testing sites targeted underserved and low-income areas which often have a higher number of Latino and African American populations, which have been reported to be disproportionately impacted by the pandemic. In a study by Rodriguez-Diaz et al, communities with high Latino populations (≥17.8% of the population) have significantly higher rates of COVID-19 compared to communities with lower Hispanic populations (<17.8% of the population) in both the Northeast (adjusted relative risk: 1.42; 95% CI 1.11–1.84) and Midwest US (adjusted relative risk: 1.70; 95% CI 1.57–1.85).[21] Despite availability of vaccines against COVID-19, the underserved and low-income areas have lower vaccination rates compared to high-income areas.[22]

During the COVID-19 waves however, the positivity rates at Vincere mobile testing site was slightly lower than the ADHS reported values. This may be attributed to the fact that the COVID-19 testing at our mobile site was available at zero-cost to all individuals (not all sites offered free testing). Since testing was offered at zero cost to the individual, people may have been more likely to get tested following exposure or symptoms. Many individuals may have also utilized the COVID-19 testing site prior to social gatherings and travel.

The results of this study yielded trends and patterns which are beneficial in public health planning and mitigation. Despite this, there are several limitations to note. This study abstracted data from case counts that were reported to Arizona Department Health Services. Despite the public health emergency mandatory reporting, there may be errors in reporting or missed reporting. The patient population between Vincere mobile program and Arizona State also differed. Vincere mobile site was from the Phoenix metropolitan area, which is the largest city in Arizona and the fourth largest city in the United States, and therefore, may not be representative of overall global trend of the pandemic. The mobile testing sites were selected to assist underserved communities, which had predominantly Latino and African American populations and low-income populations. Vincere program only tested individuals age 3 years and up, while Arizona State data would include case counts from inpatient and outpatient facilities which tested pediatric patients under the age of 3 years. Lastly, the Quidel Sofia Antigen test does not differentiate between the initial SARS-CoV and the novel SARS-CoV-2; however, as per the CDC, there are no current active cases of SARS-CoV.

The results of this study are thought provoking and hypothesis generating, but ongoing and further studies as well as application of public health programs among rural and remote areas are required. Improved reporting and studies of COVID-19 epidemiology in rural areas and in racial minorities will help assess the full impact of COVID-19 pandemic and to provide healthcare access to those needing it the most.

5. Conclusion

Cyclical trends in COVID-19 cases and positivity rates can be observed. COVID-19 cases and positivity rates increase during times of large gatherings (such as school) and holidays. Cases have also been higher following the removal of mask mandates and social gathering restrictions. The patterns and trends in COVID-19 cases and positivity rates, as observed in this study, are beneficial in planning and mitigation efforts to ensure public health safety while the nation continues to remain open while at the same time planning for future global public health crises.

Acknowledgments

We would like to thank the City of Phoenix for their partnership in the COVID-19 mobile testing project. Thank-you also to all the individuals who help at the sites each day, from operational logistics to performing and processing the tests.

Author contributions

Conceptualization: Vershalee Shukla, Pablo Prichard, Christine Lau.

Data curation: Pravneet Chadha, Hurshneet Chadha, Vershalee Shukla, Pablo Prichard, Christine Lau.

Formal analysis: Pravneet Chadha, Hurshneet Chadha, Vershalee Shukla, Pablo Prichard, Christine Lau

Funding acquisition: Vershalee Shukla, Pablo Prichard.

Investigation: Vershalee Shukla, Pablo Prichard, Christine Lau.

Methodology: Vershalee Shukla, Pablo Prichard, Christine Lau.

Project administration: Vershalee Shukla, Pablo Prichard, Christine Lau.

Resources: Vershalee Shukla, Pablo Prichard, Christine Lau.

Software: Vershalee Shukla, Pablo Prichard, Christine Lau.

Supervision: Vershalee Shukla, Pablo Prichard, Christine Lau.

Validation: Vershalee Shukla, Pablo Prichard, Christine Lau.

Visualization: Vershalee Shukla, Pablo Prichard, Christine Lau.

Writing – original draft: Pravneet Chadha, Hurshneet Chadha, Vershalee Shukla, Pablo Prichard, Christine Lau.

Writing – review & editing: Pravneet Chadha, Hurshneet Chadha, Vershalee Shukla, Pablo Prichard, Christine Lau.

Abbreviations:

ADHS

Arizona Department of Health Services

CDC

Centers for Disease Control and Prevention

COVID-19

coronavirus 2019

References

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[3]. AZDHS | COVID-19 Dashboards. Arizona Department of Health Services. [cited April 23, 2023]. Available at: https://www.azdhs.gov/covid19/data/index.php.

[4]. Gallaway MS, Rigler J, Robinson S, et al. Trends in COVID-19 incidence after implementation of mitigation measures—Arizona, January 22-August 7, 2020. MMWR Morb Mortal Wkly Rep. 2020;69:1460–3.

[5]. Office of Governor Doug Ducey | Executive Orders. Office of the Arizona Governor. [cited January 18, 2021]. Available at: https://azgovernor.gov/executive-orders.

[6]. Ducey D. Executive Order 2020-51: “Arizona Open for Learning”. State of Arizona. 2020. Available at: https://azgovernor.gov/executive-orders.

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[10]. Quidel. Sofia SARS Antigen FIA. Product specifications. [cited May 4, 2022]. Available at: https://www.quidel.com/immunoassays/rapid-sars-tests/sofia-sars-antigen-fia.

[11]. Lau CSM, Shu S, Mayer J, et al. COVID-19 trends in the Phoenix metropolitan area from a mobile testing program: last quarter of 2020. J Community Health. 2021;46:1078–82.

[12]. Lau CSM, Johns J, Merlene S, et al. Trends in COVID-19 testing and positivity rates from a mobile testing program in the Phoenix metropolitan area. J Community Health. 2021;46:1221–5.

[13]. Nishiura H, Oshitani H, Kobayashi T, et al. Closed environments facilitate secondary transmission of coronavirus disease 2019 (COVID-19). medRxiv. 2020;2020.02.28.20029272.

[14]. Leclerc QJ, Fuller NM, Knight LE, et al. What settings have been linked to SARS-CoV-2 transmission clusters? Wellcome Open Res. 2020 [cited January 9, 2021];5:83. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7327724/.

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[16]. Sassano M, McKee M, Ricciardi W, et al. Transmission of SARS-CoV-2 and other infections at large sports gatherings: a surprising gap in our knowledge. Front Med. 2020 [cited January 9, 2021];7:277. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7273227/.

[17]. Transportation Security Administration. TSA checkpoint travel numbers (current year(s) versus prior year/same weekday) | Transportation Security Administration. [cited January 22, 2021]. Available at: https://www.tsa.gov/coronavirus/passenger-throughput.

[18]. Lau H, Khosrawipour V, Kocbach P, et al. The association between international and domestic air traffic and the coronavirus (COVID-19) outbreak. J Microbiol Immunol Infect. 2020;53:467–72.

[19]. Hu M, Lin H, Wang J, et al. Risk of coronavirus disease 2019 transmission in train passengers: an epidemiological and modeling study. Clin Infect Dis. 2021;72:604–10.

[20]. Mo B, Feng K, Shen Y, et al. Modeling epidemic spreading through public transit using time-varying encounter network. Transp Res Part C Emerg Technol. 2021;122:102893.

[21]. Rodriguez-Diaz CE, Guilamo-Ramos V, Mena L, et al. Risk for COVID-19 infection and death among Latinos in the United States: examining heterogeneity in transmission dynamics. Ann Epidemiol. 2020;52:46–53.e2.

[22]. Maricopa County | Maricopa County COVID-19 Data. [cited May 4, 2021]. Available at: https://www.maricopa.gov/5671/Public-Vaccine-Data.

Keywords:

Arizona; COVID-19; mobile testing; Phoenix; SARS-CoV-2