Table 6. Main Results of Included Studies Investigating SARS-CoV-2 Transmission in Close Contact Settings.
| Study ID | Type of
transmission |
Total number of
contacts |
Cycle
threshold |
Attack rates and/or secondary attack
rates (SAR) |
Notes |
|---|---|---|---|---|---|
| Abdulrahman 2020 | Community |
Eid Alfitr
Pre-: 71,553; Post-: 76,384 Ashura Pre-: 97,560; Post-: 118,548 |
Not reported |
Eid Alfitr
Pre-: 2990 (4.2%); Post-: 4987 (6.7%); p <0.001 Ashura Pre-: 3571 (3.7%); Post-: 7803 (6.6%); p <0.001 |
The rate of positive tests was significantly greater
after religious events. |
| Adamik 2020 | Household | Unclear | Not reported | Unclear: 3553 (AR 26.7%) | |
| Afonso 2021 | Household | 267 | < 25, 25–30,
or >30 |
19.9% (95% CI 15.5–25.1; 53/267) | |
| Agergaard 2020 | Household | PCR: 5
Serology: 5 |
Not reported | Index case plus 1 family member tested
positive-PCR All 5 displayed a serological SARS-CoV-2 N/S IgG response |
|
| Akaishi 2021 | Household
Community |
2179 | Not specified | 11.9% (95% CI 10.6–13.3%; 259/2179) | |
| Angulo-Bazán 2021 | Household | 52 households
(n=236 people) 4.5±2.5 members per household |
Not reported | Serology: Amongst cohabitants, SAR was
53.0% (125 cases): 77.6% of cases were symptomatic |
Convenience sampling, no component of
temporality, selection bias. |
| Armann 2021 | Local
Household |
2045 in Phase 1
1779 in Phase 2 |
N/A | Serology: 12/2045 (0.6%)
Serology: 12/1779 (0.7%) |
|
| Arnedo-Pena 2020 | Household | 745 | Not reported | 11.1% (95% CI 9.0-13.6) | |
| Atherstone 2021 | Community | 441 | Not specified | 9.3% (41/441) | |
| Baettig 2020 | Local | 55 | Not reported | Serologic attack rates: 2/55 (3.6%) | Serological testing was positive for the 2 contacts
14 days after index case |
| Baker 2020 | Nosocomial | 44 | Not reported | 3/44 (6.8%): 1 of these was also exposed to a
household member with COVID-19. |
Recall error and bias, report is limited to a single
exposure, change in mask policy partway through the exposure period |
| Bao 2020 | Community | 57 index cases
1895 exposed |
Not reported | SAR was 3.3% at the bathing pool, 20.5% in
the colleagues’ cluster and 11.8% in the family cluster. |
Delayed detection of the activity trajectory of the
primary case, reporting bias, overlap of close contacts |
| Basso 2020 | Nosocomial | 60 HCWs - ≥106
unique high-risk contacts |
Not reported | Attack rate: 0/60 (0%)
Serology: 0/60 (0%) |
Delay in diagnosing index case, recall bias |
| Bays 2020 | Nosocomial | 421 HCWs | Not reported | 8/421 (1.9%) | In all 8 cases, the staff had close contact with the
index patients without sufficient PPE. Hospital staff developing ILI symptoms were tested for SARS- CoV-2, regardless of whether they had contact with an index patient |
| Bender 2021 | Community | 280 | Not specified | 13.3% (24/180) | |
|
Bernardes-Souza
2021 |
Household | 112 | Not specified | AR 49.1% (55/112) | |
| Bhatt 2022 | Household | 487 | N/A | 49.1% (95% CI 42.9–55.3%; 239/487) | |
| Bi 2020 | Local
Household Community |
1,296 | Not reported | 98/1286 (7.6%) | |
| Bi 2021 | Household | 4534 | Not specified | 6.6% (298/4534) | |
| Bistaraki 2021 | Household
Community |
64608 | Not specified | 17.4% (95% CI 17.0–17.8; 11232/64608). | |
| Bjorkman 2021 | Local | 6408 | Not specified | AR 16.5% (1058/6408) | |
| Blaisdell 2020 | Community | 1,022 | Not reported | 1.8% of camp attendees (10 staff members
and 8 campers) |
Travel was assumed to be from home state, but
intermediate travel might have occurred |
| Böhmer 2020 | Local
Household |
241 | Not reported | 75·0% (95% CI 19·0–99·0; three of four
people) among members of a household cluster in common isolation, 10·0% (1·2–32·0; two of 20) among household contacts only together until isolation of the patient, and 5·1% (2·6–8·9; 11 of 217) among non- household, high-risk contacts. |
|
| Boscolo-Rizzo 2020 | Household | 296 | Not reported | 74/296 (25.0%, 95% CI 20.2–30.3%) | The prevalence of altered sense of smell or taste
was by far lower in subjects negative to SARS-CoV-2 compared to both positives (p < 0.001) and non- tested cases (p < 0.001). |
| Brown 2020 | Local | 21 | Not reported | Serologic attack rate: 2/21 (1%) | Social desirability bias likely |
| Burke 2020 | Household | 445 | Not reported | 0.45% (95% CI = 0.12%–1.6%) among all close
contacts, and a symptomatic secondary attack rate of 10.5% (95% CI = 2.9%–31.4%) among household members. |
2 persons who were household members of
patients with confirmed COVID-19 tested positive for SARS-CoV-2. |
| Calvani 2021 | Local
Household |
162 children
(81 SARS-CoV-2 positive and 81 Controls) 142 contacts |
Used NAAT | School contacts 40% (28/70)
Family members 30.6% (95%CI 20.2–42.5; 22/72) |
School contacts: 70 children, 219 family members |
| Canova 2020 | Nosocomial | 21 | Not reported | 0/21 (0%) | |
| Carazo 2021 | Household | 9096 | Not specified | 29.8% (2718/9096) | |
| Cariani 2020 | Nosocomial | Unclear | 33.6 to 38.03 | 182 out of 1683 (10.8%) tested positive; 27 of
whom had close contact with COVID-positive patients |
Unclear how many HCWs had close contact;
likelihood of recall bias |
| Carvalho 2022 | Household | 182 | Not specified | 52.7% (96/182) | |
| Cerami 2021 | Household | 103 | Not specified | 32% (95% CI 22%-44%; 33/103) | |
| Charlotte 2020 | Community | 27 | Not reported | 19 of 27 (70%) tested positive | High risk of selection bias: The index case-patients
were not identified. A majority of patients were not tested for SARS-CoV-2 |
| Chaw 2020 | Local
Community |
1755 | Not reported | Close contact: 52/1755 (29.6%)
Nonprimary attack rate: 2.9% (95% CI 2.2%–3.8%) |
Potential environmental factors were not
accounted for: relative household size, time spent at home with others, air ventilation, and transmission from fomites. |
| Chen 2020 | Aircraft | 335 | Not reported | 16/335 (4.8%) | Recall bias. Did not perform virus isolation and
genome sequencing of the virus, which could have provided evidence of whether viral transmission occurred during the flight. |
| Chen 2020a | Local
Household |
209 | Not reported | 0/209 (0%) | |
| Chen 2020b | Nosocomial | 105 | Not reported | Serology: 18/105 (17.1%) | |
| Chen 2020c | Local
Community Household Nosocomial |
2147 | Not reported | 110/2147 (5.12%) | |
| Cheng 2020 | Household
Nosocomial |
2761 | Not reported | 0.70% | |
| Chu 2020 | Community | 50 exposed | Not reported | None for antigen or antibody: 0/50 (0%) | Testing was biased toward contacts who knew
the case-patient personally (office co-workers) or provided direct care for the case-patient (HCP). |
| Chu 2021 | Household | 526 exposed | Not reported | 48 (9%) (CI 7-12%) | Very high risk of selection bias |
| Contejean 2020 | Nosocomial | 1344 exposed | Not reported | 373 (28%) | |
| Cordery 2021 | Local
Household |
65 | Not specified | Overall 12.3% (8/65)
Child bubble contacts 0% (0/13) School contacts 10.3% (3/29) Child household contacts 0% (0/8) Adult household contacts 26.7% (4/15) |
|
|
COVID-19 National
Emergency Response Center 2020 |
Local
Household Nosocomial |
2370 | Not reported | 13/2370 (0.6%) | There were 13 individuals who contracted COVID-
19 resulting in a secondary attack rate of 0.55% (95% CI 0.31–0.96). There were 119 household contacts, of which 9 individuals developed COVID- 19 resulting in a secondary attack rate of 7.56% (95% CI 3.7–14.26). |
| Craxford 2021 | Household | 178 | N/A | 7.2% (13/178) | |
| Danis 2020 | Local
Household |
Chalet: 16
School: 172 |
Not reported | Attack rate: 75% in chalet
Attack rate: 0% in school |
Only 73 of 172 school contacts were tested - all
tested negative |
| Dattner 2020 | Household | 3353 | Not reported | Attack rates: 25% in children and 44% adults
(45% overall) Serology: 9/714 (1.3%) |
|
| de Brito 2020 | Household | 24 exposed | Not reported | RT-PCR: 6/7 (86%); Seropositivity: 18/24 (75%) | |
| Deng 2020 | Household | 347 | Not reported | 25/347 (7.2%) | |
| Desmet 2020 | Local | 84 | 38.8 | Attack rate: 0/84 (0%) | Ct reported for only one test result |
| Dimcheff 2020 | Community
Nosocomial Household |
1476 | Not reported | Seroprevalence 72/1476: 4.9% (95% CI,
3.8%–6.1%) |
|
| Dong 2020 | Household | 259 | Not reported | 53/259 (20.5%) | |
| Doung-ngern 2020 | Local | 211 cases plus
839 non- matched controls |
Not reported | ||
| Draper 2020 | Local
Household Nosocomial |
445 | Not reported | 4/445 (0.9%) | None of the 326 aircraft passengers or 4
healthcare workers who were being monitored close contacts became cases. |
| Dub 2020 | Local
Household |
121 | Not reported | Child index case: No positive cases
Adult index case: 8/51 (16%) Serology: 6/101 (5.9%) |
|
|
Expert Taskforce
2020 |
Local | Unclear | Not reported | Attack rate 20.4% | Attack rates were highest in 4-person cabins
(30.0%; n = 18), followed by 3-person cabins (22.0%; n = 27), 2-person cabins (20.6%; n = 491), and 1- person cabins (8%; n = 6). |
| Farronato 2021 | Household | 49 | N/A | 16.3% (8/49) | |
|
Fateh-Moghadam
2020 |
Community | 6690 | Not reported | 890/6690 (13.3%) | |
| Firestone 2020 | Local | Unclear | Not reported | 41 (80%) interviewed patients with primary
event-associated COVID-19 reported having close contact with others during their infectious period, with an average of 2.5 close contacts per patient. 36 (75%) of 48 interviewed patients with primary event-associated cases reported having close contact with persons in their household while infectious, and 17 (35%) reported having other (social/workplace) close contacts while infectious. |
|
| Fontanet 2021 | Local | 2004 | N/A | Serology: 15.3% (306/2004)
10.4% (139/1,340) - primary schools 25.1% (167/664) - high schools |
|
| Galow 2021 | Household | 248 | N/A | 34.3% (85/248) | |
|
Gamboa Moreno
2021 |
Household
Community |
Unclear | Not specified | 2.9% in preschools to 7.1% in high schools | |
| Gan 2020 | Local
Household Community |
Unclear | Not reported | Not reported | Family clusters accounted for 86.9% (914/1 050) of
cases, followed by party dinners (1.1%) |
| Gaskell 2021 | Household | 1242 | N/A | AR 64.3% (95% CI 61.6-67.0%, 799/1,242). | |
| Ge 2021 | Household
Community |
8852 | Not specified | 3.6% (95% CI 3.3%-4.0%; 327/8852) | |
| Ghinai 2020 | Community | Unclear | Not reported | Unclear | |
| Gold 2021 | Local
Household |
31 school
69 household |
Not specified | School: 48% (15/31)
Household: 26% (18/69) |
|
| Gomaa 2021 | Household | 98 | Not specified | AR 6.9% (95%CI: 5.8–8.3)
89.8% (95% CI: 82.2–94.3; 88/98) AR Serology 34.8% (95% CI: 32.2–37.4; 438/1260) |
|
| Gonçalves 2021 | Household | 271 case-
patients and 1,396 household controls |
Not specified | Not reported | |
| Gong 2020 | Household
Community |
Unclear | Not reported | Unclear | |
| Gu 2020 | Local | 14 | Not reported | RT-PCR - 3/14 (21.4%)
Serology - 2/14 (14.3%) |
|
| Hamner 2020 | Local | 60 | Not reported | Confirmed: 32/60 (53.3%)
Probable: 20/60 (33.3%) |
|
| Han 2020 | Community | 192 | Not reported | 7/192 (3.7%) | |
| Hast 2022 | Community | 628 | Not specified | 9.2% (58/628) | |
| Heavey 2020 | Local | 1155 | Not reported | 0/1155 (0%) | |
| Helsingen 2020 | Local | Training arm:
1,896 Nontraining arm: 1,868 |
Not reported | 11/1896 (0.8%) vs 27/1868 (2.4%); P=0.001 | |
| Hendrix 2020 | Local | 139 exposed | Not reported | 0% | Six close contacts of stylists A and B outside of
salon A were identified: four of stylist A and two of stylist B. All four of stylist A’s contacts later developed symptoms and had positive PCR test results for SARS-CoV-2. These contacts were stylist A’s cohabitating husband and her daughter, son-in- law, and their roommate, all of whom lived together in another household. None of stylist B’s contacts became symptomatic. |
| Hirschman 2020 | Household
Community |
58 | Not reported | 27/58 (47%) | |
| Hobbs 2020 | Local
Household Community |
397 | Not reported | Not reported | |
| Hoehl 2021 | Local
Community |
825 children and
372 staff: 7,366 buccal mucosa swabs and 5,907 anal swabs |
Not reported | 0% viral shedding in children; 2/372
(0.5%) shedding for staff. No inapparent transmissions were observed |
Study was conducted in the summer of 2020, when
activity of other respiratory pathogens was also low |
| Hong 2020 | Household | 431 tests | Not reported | 0/13 (0%) | Index cases had lived with their family members
without personal protections for a total of 258 person-days. |
| Hsu 2021 | Household | 145 | Not specified | 46.2% (47/145) | |
| Hu 2020 | Community | 72093 | Not specified | 0.32% (95%CI 0.29% –0.37%; 234/72093) | |
| Hu 2021 | Household
Community |
15648 | Not reported | 471/15648 (3%) | |
| Hu 2021 | Local | 5622 | Not specified | 0.6% (95% CI 0.43 - 0.84%; 34/5622) | |
| Hua 2020 | Household | 835 | Not reported | 151/835 (18.1%) | |
| Huang 2020 | Household
Community |
22 | Not reported | 7/22 (31.8%) | |
| Huang 2020a | Local
Household Community Nosocomial |
3795 | Not reported | 32/3795 (0.84%) | |
| Huang 2021 | Nosocomial | 211 | Not specified | 3.8% (8/211) | |
| Islam 2020 | Household
Local Community Nosocomial |
391 | Not reported | The overall secondary clinical attack rate was
4.08 (95% CI 1.95-6.20) |
|
| Jashaninejad 2021 | Household | 989 | Not specified | 31.7% (95% CI: 28.8-34.7) | |
| Jeewandara 2021 | Household
Community |
1093 | Not specified | 7.8% (85/1093) - PCR
1.7% (7/439) - antibodies |
|
| Jia 2020 | Household | Unclear | Not reported | Attack rate 44/583 (7.6%) | |
| Jiang 2020 | Household
Community |
300 | Not reported | 6/300 (2%) | |
| Jing 2020 | Household | Unclear | Not reported | Household contacts 13·2%
Non-household contacts 2·4% |
The risk of household infection was significantly
higher in the older age group (≥60 years) |
| Jing 2020a | Household
Community |
Unclear | Not reported | Close contacts 17.1% to 19%
Family members 46.1% to 49.6% |
|
| Jones 2021 | Local | 128 | Not reported | 6/128 (4.7%) | |
| Jordan 2022 | Local | 253 | Not specified | 4.7% (12/253) | |
| Kang 2020 | Local | 5517 | Not reported | 96/5517 (1.7%) | |
| Kant 2020 | Local
Community Nosocomial |
Not reported | Not reported | Not reported | No details on number of contacts for index case |
|
Karumanagoundar
2021 |
Household
Community |
15702 | Not specified | 4% (599/14 002) | |
| Katlama 2022 | Household | 255 | N/A | 37.3% (95%CI 31.3–43.5%; 95/255) | |
| Kawasuji 2020 | Nosocomial | 105 | Not reported | 14/105 (1.33%) | |
| Khanh 2020 | Community | 217 | Not reported | 16/217 (7.4%) | |
| Kim 2020 | Household | 207 | 17.7 to 30 | 1/207 (0.5%) | |
| Kim 2020a | Household
Community |
4 | 18.7 to 32.1 | N/A | |
| Kim 2020b | Nosocomial | 3,091 respiratory
samples from 2,924 individuals |
Not reported | 3/290 (1%) | |
| Kim 2021 | Local | 8 | N/A | 0% RT-PCR
0% Serology |
Tests for anti-SARS-CoV-2 antibodies were
performed on quarantined HCWs on the 52nd day from exposure. All serologic test results, including FIA IgM and IgG and ELISA total antibody, were negative. |
| Kitahara 2022 | Household
Community |
114 | Not specified | 15% (17/114) | |
| Klompas 2021 | Nosocomial | 1457 | Not specified | 2.6% (38/1457) | |
| Kolodziej 2022 | Household | 241 | Not specified | 64.3% (155/241) | SAR for household was 75/85 (88.6%) |
| Koureas 2021 | Household | 286 | Not specified | 38.6% (95% CI: 32.50–45.01%) | |
| Kumar 2021 | Community | 822 | Not reported | 144/822 17.5%) | Spread of infection within the state was significantly
higher from symptomatic cases, p=0.02 |
| Kuwelker 2021 | Household | 179 | N/A | 45% | The elderly (>60 years old) had a significantly
higher attack rate (72%) than adults< 60years old (46%, p=0·045) |
| Kuwelker 2021 | Household | 291 | N/A | AR 45% (95% CI 38–53) | |
| Kwok 2020 | Local
Household |
206 | Not reported | 24/206 (11.7%) | |
| Ladhani 2020 | Nosocomial | 254 | Not reported | Unclear: 53/254 (21%) tested positive. | Staff working across different care homes (14/27,
52%) had a 3.0-fold (95% CI, 1.9–4.8; P<0.001) higher risk of SARS-CoV-2 positivity than staff working in single care homes (39/227, 17%). |
| Ladhani 2020a | Nosocomial | Residents: 264
Staff members: 254 |
Not specified | Unclear: 105/264 (53%) residents tested
positive |
Infectious virus recovery in asymptomatic staff and
residents emphasises their likely importance as silent reservoirs and transmitters of infection and explains the failure of infection control measures which have been largely based on identification of symptomatic individuals. |
| Laws 2020 | Household | 188 | Not reported | 55/188 (29.3%) | |
| Laws 2021 | Household | 188 | Not specified | 29.3% (55/188); | |
| Laxminarayan 2020 | Local
Household Community |
575,071 | Not reported | 10.7% (10.5 to 10.9%) for high-risk contacts
4.7% (4.6 to 4.8%) for low-risk contacts 79.3% (52.9 to 97.0%) for high-risk travel exposure |
|
| Lee 2020 | Household | 12 | Not reported | 0/12 (0%) | |
| Lee 2020a | Household | 23 | Not reported | 1/23 (4.4%) | |
| Lewis 2020 | Household | 188 | Not reported | RT-PCR: 55/188 (29%)
Serology: 8/52 (15%) |
|
| Li 2020 | Household | 5 | 19.66 to 26.16 | 4/5 (80%) | |
| Li 2020a | Household
Nosocomial |
7 | Not reported | 7/7 (100%) | During January 14–22, the authors report that
index patient had close contact with 7 persons |
| Li 2020b | Household | 14 | Not reported | 14/14 (100%) | |
| Li 2020c | Household | Unclear | Not reported | Unclear | In COFs, the transmission rates of respiratory
droplets in secondary and non-infected patients were 11.9 % and 66.7 %, respectively, while the transmission rates of respiratory droplets with close contacts were 88.1 % and 33.3 %, respectively. In SOFs, the proportion of respiratory droplet and respiratory droplet transmission with close contacts was 40 % and 60 %, respectively |
| Li 2020d | Household | 392 | Not reported | 64/392 (16.3%) | |
| Li 2021a | Household | 52822 | Not specified | 16·0% (15·7–16·3; 8447/52822) | |
| Li 2021b | Household
Community |
2382 | Not specified | 6.50% | |
| Lin 2021 | Household | 5 | Not specified | PCR 80%
Serology 80% |
|
| Liu 2020 | Household | 7 | Not reported | 4/7 (57.1%) | |
| Liu 2020a | Nosocomial | 30 | Not reported | N/A | |
| Liu 2020b | Household
Community Nosocomial |
11580 | Not reported | 515/11580 (4.4%) | |
| Liu 2020c | Unclear | 1150 | Not reported | 47/1150 (4.1%) | The 16 confirmed cases who had previously been
asymptomatic accounted for 236 close contacts, with a second attack rate of 9.7%, while the remaining 131 asymptomatic carriers accounted for 914 close contacts, with a second attack rate of 2.6% (p<0.001) |
| Liu 2021 | Household | 50 | Not specified | 34% (95% CI: 22%–48%; 17/50) | |
| López 2020 | Local
Household |
285 | Not reported | Facility SAR: 22/101 (21.8%)
Overall SAR: 38/184 (20.7%) |
Variation in hygiene procedures across 3 facilities.
Facility A required daily temperature and symptom screening for the 12 staff members and children and more frequent cleaning and disinfection; staff members were required to wear masks. Facility B: temperatures of the five staff members and children were checked daily, and more frequent cleaning was conducted; only staff members were required to wear masks. Facility C: 84 staff members and children check their temperature and monitor their symptoms daily; masks were not required for staff members or children. |
| López 2021 | Household | 229 | Not specified | 53.7% (123/229) | |
| Lopez Bernal 2020 | Household
Community |
472 | Not reported | 37% (95% CI 31-43%) | |
| Lopez Bernal 2022 | Household | 472 | Not specified | 37% (95% confidence interval (CI): 31–43) | |
| Lucey 2020 | Nosocomial | Not specified | N/A | Not reported | |
| Luo 2020 | Community | 243 | Not reported | 12/243 (4.9%) | No viral genetic sequence data were available
from these cases to prove linkage; and some of the secondary and tertiary cases could have been exposed to unknown infections, especially asymptomatic ones, before or after the bus trips. |
| Luo 2020a | Household
Community Nosocomial |
3410 | Not reported | 127/3410 (3.7%) | |
| Lyngse 2020 | Household | 2226 | Not reported | 371/2226 (16.7%) | |
| Ma 2020 | Unclear | 1665 | Not reported | 10/1/1665 (0.6%) | Only close contacts who fell ill were tested (n=10) |
| Macartney 2020 | Local | 633 | Not reported | 18/633 (1.2%)
Serologic attack rates: 8/171 (4.8%) |
|
| Malheiro 2020 | Household | 1627 | Not reported | Overall AR 154/1627 (9.5%) | |
| Maltezou 2020 | Household | Unclear | <25 (28.1%)
25-30 (26.8%) >30 (45.1%) |
Median attack rate 40% (range: 11.1%–100%)
per family. |
|
| Maltezou 2020a | Household | Unclear | Not reported | Median attack rate: 60% (range: 33.4%-100%) | Adults were more likely to develop a severe clinical
course compared to children (8.8% versus 0%, p- value=0.021) |
| Mao 2020 | Household
Local |
Unclear | Not reported | 6.10% | Average attack rate was 8.54% (1.02–100%) |
| Martínez-Baz 2022 | Household
Community |
59900 | Not specified | 34.9% (20905/59900) | |
|
Martinez-Fierro
2020 |
Unclear | 81 | Not reported | 34/81 (42%)
Serologic attack rates: 13/87 (14.9%) |
16% of contact showed positive serology after >2
weeks |
| McLean 2022 | Household | 404 | Not specified | 49% (198/404) | |
|
Mercado-Reyes
2022 |
Household | 17863 | N/A | AR Serology 32.3% (5811/17,863) | |
| Metlay 2021 | Household | 17917 | Not specified | 10.1% (1809/17 917) | |
| Meylan 2021 | Nosocomial | 1874 | N/A | AR Serology 10.0% (95%CI 8.7% to 11.5%;
188/1874) |
|
| Miller 2021 | Household | 431 | <20 to 40 | PCR 21.1% (91/431)
Serology 46.9% (180/431) |
|
| Montecucco 2021 | Local | 346 | Not specified | 9.8% (34/346) | |
| Mponponsuo 2020 | Nosocomial | 38 | N/A | 0/38 (0%) | |
| Musa 2021 | Household | 793 | Not specified | 17% (95%CI 14–21) | |
| Ng 2020 | Household
Local Community |
13026 | Not reported | 188/7770 (2.4%)
Household: 5·9% Work contacts: 1.3% Social contacts: 1.3% Serology: 44/1150 (3.8%) |
Serology results were positive for 29 (5·5%) of
524 household contacts, six (2·9%) of 207 work contacts, and nine (2·1%) of 419 social contacts. |
| Ng 2021 | Household | 848 | Not specified | 55% (466/848) | |
| Ning 2020 | Household
Local Community |
Unclear | Not reported | Imported cases: 69/3435 (0.8%)
Local cases: 31/3666 (2.0%) |
|
| Njuguna 2020 | Local | 98 | Not reported | Attack rate 57% to 82% | |
| Nsekuye 2021 | Local
Household Community |
1035 | Not specified | 3.5% (36/1035) | |
| Ogata 2021 | Household | 496 | Not specified | 25.2% (21.6–29.2; 125/496) | |
| Ogawa 2020 | Nosocomial | 30 PCR/serology | 33.53 to
36.83 |
0/15 (0%) for both PCR and serology | |
| Paireau 2022 | Household
Local Nosocomial |
6028 | Not reported | 248/6028 (4.1%) | Family contacts, index case was 60-74, or older
than 75 years old were significantly associated with increased odds of transmission. The proportion of nosocomial transmission was significantly higher than in contact tracing (14% vs 3%, p<0.001) |
| Pang 2022 | Local | 164 | Not specified | 9.8% (16/164) | |
| Park 2020 | Local
Household Community |
328 | 17.7 to 35 | 22/328 (6.7%) | |
| Park 2020a | Household
Non- household |
59,073 | Not reported | Household contacts: 11.8% (95% CI 11.2%–
12.4%) Non-household contacts: 1.9% (95% CI 1.8%–2.0%) |
|
| Park 2020b | Local
Household |
441 | Not reported | Attack rate 43.5% (95% CI 36.9%–50.4%)
Secondary attack rate 16.2% (95% CI 11.6%– 22.0%) |
|
| Passarelli 2020 | Nosocomial | 6 | Not reported | 2/6 (33.3%) | |
| Patel 2020 | Household | 185 | Not reported | 79/185 (43%) | Contacts not reported as tested |
| Pavli 2020 | Aircraft | 891 | Not reported | 5/891 (0.6%) | |
| Petersen 2021 | Household | 584 | N/A | 19.2% (11/584) | |
| Pett 2021 | Household
Community |
392 | Not specified | 3.3% (13/392) | |
| Phiriyasart 2020 | Household | 471 | Not reported | 27/471 (5.7%) | |
| Poletti 2020 | Unclear | 2484 | Not reported | 2824/5484 (51.5%) | |
| Powell 2022 | Local | 183 | Not specified | 8.2% (15/183) | |
| Pung 2020 | Local
Community |
425 | Not reported | 36/425 (8.5%) | |
| Pung 2020a | Household | Unclear | Not reported | 43/875 (4.9%) | |
| Qian 2020 | Local
Household Community |
Not reported | Not reported | Not reported | Home‐based outbreaks were the dominant
category (254 of 318 outbreaks; 79.9%), followed by transport‐based outbreaks (108; 34.0%) |
| Ratovoson 2022 | Household | 179 | Not specified | 31.3% (56/179) | |
| Ravindran 2020 | Local | Not reported | Not reported | Attack rate 61% to 77% | All attendees participated in activities resulting
in potential exposure, such as shaking hands, kissing, dancing, sharing drinks and sharing shisha (smoking water pipes). |
| Razvi 2020 | Nosocomial | 2521 | Not reported | Serologic attack rate 19.4% | |
| Reukers 2021 | Household | 187 | Not specified | 43% (95% CI, 33%–53%) | |
|
Robles Pellitero
2021 |
Household | Not specified | Not specified | 29.8% (SAR/family) | |
| Rosenberg 2020 | Household | 498 | Not reported | 286/498 (57%) | |
| Roxby 2020 | Nosocomial | 142 | Not reported | Attack rate in 1st round: 5/142 (3.5%) | One additional positive test result was reported for
an asymptomatic resident who had negative test results on the first round. |
| Sakamoto 2022 | Nosocomial | 517 | Not specified | 8.1% (42/517) | |
| Sang 2020 | Household | 6 | Not reported | 4/6 (66.7%) | |
| Sarti 2021 | Local | 5 | Not specified | 80% (4/5) | |
| Satter 2022 | Local
Household |
684 | Not specified | RT-PCR 13% (87/684) | |
| Schoeps 2021 | Local | 14591 (13,005
PCR-tested) |
Not specified | 1.51 (95% CI 1.30–1.73) | |
| Schumacher 2021 | Local | Quarantine
phase: 757 tests Match phase: 1167 tests |
Unclear | Quarantine phase AR: 3.6%
Match phase AR: 4.2% Serology: 1.1% |
|
| Schwierzeck 2020 | Nosocomial | 48 | 16.03 to 32.98 | 9/48 (18.8%) | Ct values of symptomatic cases were significantly
lower compared to asymptomatic cases 22.55 vs 29.94, p<0.007 (approximately 200-fold higher viral load) |
| Semakula 2021 | Household
Community |
11809 | Not specified | Overall 1.77% (95% CI 1.55% to 2.02%;
209/11809) SAR of households 2.93% (95% CI 1.85% to 4.60%) |
|
| Shah 2020 | Household | 386 | Not reported | 34/386 (8.8%) | |
| Shah 2021 | Household | 287 | Not specified | 1.7% (95%CI 0.7–4%) | |
| Shen 2020 | Household
Community |
480 | Not reported | Close contact: 2/7 (29%)
Casual contact: 3/473 (0.6%) |
|
| Sikkema 2020 | Nosocomial | 1796 | Not
specified. WGS for Ct <32 |
Attack rate 96/1796 (5%) | 46 (92%) of 50 sequences from health-care workers
in the study were grouped in three clusters. Ten (100%) of 10 sequences from patients in the study grouped into the same three clusters: |
| Son 2020 | Household | 3223 | Not reported | 8.2% (95% CI, 4.7 to 12.9) | |
| Song 2020 | Household | 20 | Not reported | 16/20 (80%) | |
| Sordo 2022 | Household | 659 | Not specified | 22.5% (148/659). | |
|
Soriano-Arandes
2021 |
Household | 283 | Not specified | 59% (167/283) | |
| Speake 2020 | Aircraft | 111 | Not reported | 11/111 (9.9%) | |
| Stein-Zamir 2020 | Local | 1312 | Not reported | Attack rate 178/1312 (13.6%) | |
| Stich 2021 | Household | 1,220 | Not specified | RT-PCR 32.8% (400/1220)
Serology 36.1% (393/1,090) |
|
| Sugano 2020 | Local | 72 | Not reported | 23/72 (31.9%) | |
| Sun 2020 | Household | Unclear | Not reported | 34.43% | |
| Sun 2021 | Household | 50 | Not specified | 14.0% (7/50) | |
| Sundar 2021 | Household
Community |
496 | Not specified | 16.7% (83/496) | |
| Tadesse 2021 | Household | 40 households | N/A | AR 3.5% (95% CI: 3.2%-3.8%) | |
| Tanaka 2021 | Household | 687 | Not specified | 28.2% (194/687) | |
| Tanaka 2022 | Household | 101 households
with 477 individuals |
Not specified | 77.0% (95% CI: 69.4-84.6%) | |
| Taylor 2020 | Nosocomial | 600 | Not reported | Resident attack rate: 137/259 (52.9%) 1st round
HCW Attack rate: 114/341 (33.4%) |
|
| Teherani 2020 | Household | 144 | Not reported | 67/144 (46.5%) | Of the total number of household contacts, at least
29 (20%) had known SARS-CoV2 testing. Child-to-adult transmission was suspected in 7/67 cases (10.5%). |
| Thangaraj 2020 | Community | 26 | Not reported | 17/26 (65.4%) | |
| Torres 2020 | Community | 1244 | N/A | Overall serologic attack rate: 139/1244
(11.2%) |
|
| Tsang 2022 | Household
Community |
3158 | Not specified | 3.5% (95%CI 2.9–4.3) | |
| Tshokey 2020 | Local
Community |
1618 | Not reported | 14/1618 (0.9%) | SAR: High-risk contacts was 9.0% (7/75), and that
among the primary contacts was 0.6% (7/1,095), and none (0/448) among the secondary contacts. |
| Tsushita 2022 | Local | 23 | Not specified | 69.6% (16/23) | |
| van der Hoek 2020 | Household | 174 | 25.1 to 35.1 | 47/174 (27%)
Serology on day 3 - family members: 43/148 (29.1%) |
|
| Vičar 2021 | Household | 226 | Not specified | 22.6% (51/226) | |
| Wang 2020 | Nosocomial
Household |
43 | Not reported | 10/43 (23.3%) | |
| Wang 2020a | Household | 155 | Not reported | 47/155 (30%) | |
| Wang 2020b | Household | 335 | Not reported | 77/335 (23%) | |
| Wee 2020 | Nosocomial | 298 | Not reported | 1/298 (0.3%) | |
| Wendt 2020 | Nosocomial | 254 | Not reported | 0/254 (0%)
Serologic attack rates 0/23 (0%) |
|
| White 2022a | Local | 485 | Not specified | 4.1% (20/485) | |
| White 2022b | Local | 859 | Not specified | 7% (60/859) | |
| Wiens 2021 | Household | 435 households | N/A | AR 38.5% (32.1 - 46.8) | |
| Wolf 2020 | Household | 4 | Not reported | 3/4 (75%) | 7-month-old female who was breastfed, was
asymptomatic throughout the observation period and never developed fevers or any other symptoms, despite continuous exposure to her parents and siblings. She remained SARS-CoV-2 PCR-negative in repeat testing of pharyngeal swab and stool specimens over the entire observation period. |
| Wong 2020 | Nosocomial | 76 tests were
performed on 52 contacts |
Not reported | 0/52 (0%) | Findings suggest that SARS-CoV-2 is not spread
by an airborne route. Ct value for throat and tracheal aspirate of index case were 22.8 and 26.1 respectively. |
| Wood 2021 | Household | Not reported | Not reported | Not reported | |
| Wu 2020 | Household
Local Community |
2994 | Not reported | 71/2994 (2.4%) | |
| Wu 2020a | Household | 148 | Not reported | 48/148 (32.4%) | |
| Wu 2021 | Local
Household Community |
4214 | Not specified | 3.3% (140/4214) | |
| Xie 2020 | Household | 56 | Not reported | 0/56 (0%) | |
| Xie 2021 | Household | 79 | Not specified | 67.1% (53/79) | |
| Xin 2020 | Household | 187 | Not reported | 19/187 (17.9%) | |
| Yang 2020 | Household
Local |
1296 | Not reported | 0/1296 (0%)
Serologic attack rates: 0/20 (0%) |
Viral cultures of 4 specimens with Ct <30 were
negative. |
| Yau 2020 | Nosocomial | 330 | Not reported | 22/330 (6.7%) | |
| Ye 2020 | Local
Community |
1293 | Not reported | 39/1,293 (3.02%) | |
| Yi 2021 | Household | 475 | <37 | 42.9% (204/475) | |
| Yoon 2020 | Local | 190 | N/A | 0/190 (0%) | |
| Yousaf 2020 | Household | 198 | Not reported | 47/198 (23.7%) | |
| Yu 2020 | Household | 1587 | Not reported | 150/1587 (9.5%) | |
| Yung 2020 | Household | 213 | Not reported | Attack rate 6.1% | |
| Zhang 2020 | Aircraft | 4492 | Not reported | Attack rate 161/4492 (3.6%) | The authors report attack rate of 0.14% based on
94 flights (n=14 505); however, only 4492 people were screened. |
| Zhang 2020a | Household
Local Community |
369 | Not reported | 12/369 (3.3%, 95% CI 1.9%–5.6%) | |
| Zhang 2020b | Household | 10 | Not reported | 0/10 (0%)
Serologic attack rates: 0/10 (0%) |
|
| Zhang 2020c | Local
Household |
93 | Not reported | 5/93 (5.4%) | |
| Zhang 2020d | Local | 8437 | Not reported | 25/8437 (0.3%) | |
| Zhang 2021 | Local
Household |
178 | ≤38 | 7.3% (13/178) | |
| Zhuang 2020 | Household
Community |
8363 | Not reported | 239/8363 (2.9%) |