Demographics of study participants
A total of 2,808 out of 9,242 event attendees (30.4%) enrolled in our study. Study participants were on average 23.8 years old (± 2.7, range 19–56 years), and the majority were female (62.4%, see Table 1). 86.2% of the participants were medical students (45%) or reported to be working in the health care sector (41.2%). With mostly German residents enrolled (94.1%) only a few participants reported to be traveling from other European countries. Concerning health status, 28.1% of participants stated to have allergies, and 1.3% of individuals reported having an immune deficiency. 95 out of 2,808 individuals (3,4%) reported that they had a COVID-19 infection before the study period. 6.5% reported being active smokers. Other than that, individuals were believed to be healthy with a median BMI of 21.9 (± 2.5).
Table 1
Demographics of all study participants
Demographics
|
All responses
|
Age in years, n = 2808
|
Mean (SD)
|
23.8 (± 2.7)
|
Gender, n = 2798
|
Female
|
1747 (62.4%)
|
Male
|
1049 (37.5%)
|
Diverse
|
2 (0.1%)
|
BMI in kg/m², n = 2678
|
Mean (SD)
|
22.4 (± 3)
|
Any chronic disease, n = 2635
|
Allergies
|
741 (28.1%)
|
Others
|
187 (7.1%)
|
Immune deficiency, n = 2782
|
Immune deficiency
|
35 (1.3%)
|
Smoking, n = 2784
|
Active smoker
|
180 (6.5%)
|
Healthcare profession, n = 2735
|
Medical student
|
1231 (45%)
|
Hospital
|
702 (25.7%)
|
Doctors' office
|
112 (4.1%)
|
Nursing facility or retirement home
|
12 (0.4%)
|
Other medical field
|
302 (11%)
|
Not health care sector
|
376 (13.7%)
|
Residency, n = 2808
|
Germany
|
2633 (94.1%)
|
Abroad
|
165 (5.9%)
|
COVID-19 immunity*, n = 2808
|
Full immunity
|
2808 (100%)
|
Type of COVID-19 vaccine**, n = 2062
|
|
2x BioNTech
|
1224(59.4%)
|
2x Moderna
|
234 (11.3%)
|
2x Astra Zeneca
|
97 (4.7%)
|
1x Johnson & Johnson
|
27 (1.3%)
|
2x Any combination
|
480 (23.3%)
|
Table 1: Demographics of study participants. If not stated differently, all numbers displayed are n (%). Percentages are calculated from n responses to each question. *COVID-19 immunity (vaccination and/or prior infection) as controlled at event entrance 09/02/2021. **Displaying answers of participants that reported their full vaccine status only.
During the study period, 209 participants reported a total of 776 symptoms and 1,787 participants reported a total of 5,255 COVID-19 tests. This translated to an average reporting of 0.3 symptoms and 1.9 tests per enrolled participant. All participants filled out the demographics questionnaire and 59% of participants filled out at least one of the maximum three monthly COVID-19 exposition questionnaires. After the MG, we saw a decrease in reported tests and symptoms (Fig. 5). Participants that completed all three of the monthly questionnaires reported on average 0.3 more symptoms and 3.7 more tests than participants that only reported one of the monthly questionnaires, indicating an association between the completion of the monthly questionnaire and the overall activity of participants in the study. The in-app feedback of 41 eCOV study participants during the study period (September, October 2021) resulted in a rating of 4.2 out of 5 stars.
We detected a total of 24 PCR-confirmed COVID-19 cases and 26 probable COVID-19 cases during the entire study period. During the 14-day surveillance period (09/04/2021–09/17/2021) where COVID-19 cases could be attributable to the MG, we registered seven confirmed (PCR positive) and seven probable cases (Fig. 2). The seven confirmed COVID-19 cases per 2,808 participants translated to an estimated seven-day incidence of ~ 125 per 100,000 participants (95% CI [67.7/100,000, 223/100,000]), which was comparable to the average age-adjusted incidence in Germany during this time (calendar weeks 36 and 37: 118.3/100,000). Within the surveillance period, six probable and six confirmed COVID-19 cases were already registered in the first week, translating to an estimated seven-day incidence of ~ 213 confirmed cases per 100,000 participants (95%CI [135.8/100,000, 332.9/100,000]). In comparison, the age-adjusted incidence in Germany during this time was 131.9/100,000. During the second week of the surveillance period, one more probable and one more confirmed case was detected, translating to an estimated seven-day incidence of ~ 36 confirmed cases per 100,000 participants (95% CI [8/100,000, 104.8/100,000]). Overall, the number of weekly COVID-19 cases detected in our app varied over the study period, with some calendar weeks before and after the event (calendar weeks 34, 35, 38, 40) where we did not detect any confirmed cases and weeks where the seven-day incidence was comparable to the Germany-wide age-matched incidence (calendar weeks 36, 39, 41, 43).
Individuals classified as confirmed COVID-19 cases during the surveillance period were primarily female (85.7%, see Table 2) and on average 23.9 years old (SD ± 2.7). Four out of seven reported living outside of Germany. All confirmed cases in the surveillance period were fully vaccinated non-smokers and did not report any immune deficiencies. None of the confirmed cases were infected with COVID-19 before the study period and none of them reported any symptoms during the infection.
Table 2
Demographics by COVID-19 infection status
|
Total
n = 2808
|
No
COVID-19
n = 2794
|
Probable COVID-19
n = 7
|
Confirmed COVID-19
n = 7
|
Demographics
|
|
|
|
|
Age in years
|
|
|
|
|
Mean (SD)
|
23.8 (± 2.7)
|
23.8 (± 2.7)
|
24.9 (± 4.2)
|
23.9 (± 2.7)
|
Gender
|
|
|
|
|
Female
|
1747 (62.4%)
|
1738 (62.2%)
|
3 (42.9%)
|
6 (85.7%)
|
Male
|
1049 (37.5%)
|
1044 (37.4%)
|
4 (57.1%)
|
1 (14.3%)
|
Diverse
|
2 (0.1%)
|
2 (0.1%)
|
-
|
-
|
Risk Profile
|
|
|
|
|
BMI in kg/m²
|
|
|
|
|
Mean (SD)
|
22.4 (± 3)
|
22.4 (± 3)
|
22.1 (± 2.6)
|
21.9 (± 2.5)
|
Any chronic disease
|
|
|
|
|
Allergies
|
741 (26.4%)
|
737 (26.4%)
|
2 (28.6%)
|
2 (28.6%)
|
Others
|
187 (6.6%)
|
185 (6.6%)
|
1 (14.3%)
|
1 (14.3%)
|
Immune deficiency
|
|
|
|
|
|
35 (1.2%)
|
35 (1.3%)
|
-
|
-
|
Active smoker
|
|
|
|
|
|
180 (6.4%)
|
178 (6.4%)
|
3 (42.9%)
|
-
|
Symptoms, amount
|
|
|
|
|
Study period*
|
|
|
|
|
CLI
|
172
|
167
|
5
|
-
|
Other
|
604
|
592
|
12
|
-
|
Surveillance period**
|
|
|
|
|
CLI
|
53
|
48
|
5
|
-
|
Other
|
184
|
172
|
12
|
-
|
Table 2: Demographics by COVID-19 infection status. If not stated differently, all numbers are displayed as n (%). Percentages are calculated from n individuals in each group. CLI = Corona Like Illness defined as having fever AND/OR cough AND/OR loss of taste or smell. *Study period: 08/12/2021–10/31/2021, ** Surveillance period: 09/04/2021–09/17/2021