Table 3.
COVID-19 infections in respondents enrolled in 2019–2021.
| Description of Participants/Respondents | Respondents/Total Participants or Respondents (N/N; %) | IgG-Positive Respondents (N/N; %) | IgG-Negative Respondents (N/N; %) |
|---|---|---|---|
| Participants | |||
| All participants, 2019–2021 | 310 (100) | 70/310 (22.5) | 240/310 (77.5) |
| Available for phone survey | 251/310 (81) | ||
| Agreed to answer (respondents) | 238/310 (77) | 59/310 (19) | 179/310 (58) |
| Refused to answer | 13/310 (4) | ||
| Unavailable for phone survey | 59/310 (19) | ||
| Respondents | |||
| Symptoms and severity of respiratory disorders | 238 (100) | ||
| Any symptoms reported | 93/238 (39) | 30/59 (37) | 63/179 (35) |
| No symptoms reported | 145/238 (61) | 40/59 (63) | 105/179 (65) |
| COVID-19 verified by PCR | 85/93 (91) | 30/93 (32) | 55/93 (59) |
| Severity of respiratory disorders | |||
| Mild | 44/93 (47) | 15/30 (50) | 28/63 (44) |
| Medium (cough, cold, and fever) | 38/93 (41) | 12/30(40) | 26/63 (41) |
| Severe (hospitalization) | 11/93 (12) | 3/30 (10) | 9/63 (14) |
| Vaccination status | 238 (100) | 59 (100) | 179 (100) |
| Vaccinated (from September 2020 to October 2021) | 137/238 (58) | 33/59 (56) | 104/179 (58) |
| Not vaccinated | 97/238 (40) | 25/59 (42) | 72/179 (40) |
| Cannot answer | 4/238 (2) | 1/59 (2) | 3/179 (2) |
| Brand of vaccine in respondents who were able to answer | 119 (100) | ||
| Gam-COVID-Vac (Sputnik V) | 103/119 (87) | ||
| Other vaccines: | 16/119 (13) | ||
| CoviVac | 7/119 (6) | ||
| EpiVacCorona | 5/119 (4) | ||
| Sputnik Lite | 4/119 (3) | ||
| Vaccinated before enrolment, IgG-status (Gam-COVID-Vac, N = 13; CoviVac, N = 1) | 14/238 (6) | 9/14 (64) | 5/14 (36) |
| Days from vaccination to the enrollment visit | 9–151 * | 117–169 * | |
| COVID-19 disease status | 238 (100) | 59 (100) | 179 (100) |
| COVID-19 verified with PCR-tests | 94/238 (40) | 27/59 (46) | 66/179 (37) |
| Not verified | 144/238 (60) | 31/59 (54) | 113/179 (63) |
| IgG-positive respondents who were able to recall the date of respiratory disorders | 59 (100) | ||
| Reported a relapse of respiratory disorders after the enrollment visit during 10–629 days of follow-up | 12/59 (20) ** | ||
| Reported a respiratory disorder before the enrollment visit during 27–476 of days follow-up | 21/59 (36) | ||
| COVID-19 verified by PCR-tests | 16/21(76) | ||
| No respiratory disorders reported | 26/59 (44) | ||
| Asymptomatic | 2/21 (10) | ||
| Mild | 10/21(48) | ||
| Medium (cough, cold, and fever) | 8/21 (38) | ||
| Severe (hospitalization) | 1/21 (5) | ||
| Severity grade of respiratory disorders after the enrollment visit in IgG -positive respondents who were able to answer | 12 (100) | ||
| COVID-19 verified by PCR-tests | 12/12 (100) | ||
| Asymptomatic | 1/12(8) | ||
| Mild | 6/12 (50) | ||
| Medium (cough, cold, and fever) | 4/12 (33) | ||
| Severe (hospitalization) | 1/12 (8) | ||
| All vaccinated respondents | 137 (100) | ||
| Vaccinated respondents who were able to recall the date of respiratory disorders | 118/137 (86) | ||
| Respondents with reported respiratory disorders before vaccination | 39/118 (33) | ||
| Respondents with reported relapse of COVID-19 in vaccinated subjects verified by PCR-tests (from 92 to 183 days after the vaccination; mean 152 days) | 3/79 (4) ** | 1/3 (33.3) | 2/3 (66.7) |
| Severity grade of relapse respiratory disorders in vaccinated respondents | |||
| Mild | 2/79 (3) | ||
| Medium (cough, cold, and fever) | 1/79 (1) | ||
| Severe (hospitalization) | - | ||
(Bold) Differences in days from vaccination to the enrollment visit * t-test, p < 0.05. A relapse of respiratory disorders after the enrollment visit during ** Odds ratio = 5.4 (CI: 1.4–19.8, p = 0.01) for IgG-positive respondents with reported relapse of respiratory disorders versus vaccinated respondents who reported relapse of COVID-19.