Table 3. Definitions and descriptions of close contacts.
| Study ID | Definitions of close contacts | Definition of other contacts | Contact duration & proximity |
|---|---|---|---|
| Abdulrahman 2020 | Not defined | Not reported | Not reported |
| Adamik 2020 | Not defined | Other cases in each of the infected households were
regarded as secondary cases |
Not reported |
| Agergaard 2020 | Not defined | Not reported | 2 weeks |
| Angulo-Bazán 2020 | Not defined | Not reported | Not reported |
| Armann 2020 | Not defined | Not reported | Not reported |
| Arnedo-Pena 2020 |
Close contacts living in the same household of the index case and no other
sources of transmission apart from the index case could be found. |
Closed contacts from work, social events, relatives live
in other household were excluded and index cases live alone. |
Not reported |
| Baker 2020 | Not defined | Not reported | Median cumulative time spent with the patient 45 mins
(10–720 mins) |
| Baettig 2020 |
Close contact: Less than 2 m for more than 15 min in the last 48 hours before
onset symptom of the COVID-19 positive index patient. |
Not reported | <2m for >15 mins 48 hours before onset symptom of the
COVID-19 positive index patient |
| Bao 2020 | Not defined | Not reported | Average stay duration of 2.5 hr daily before the COVID‐19
outbreak. |
| Basso 2020 |
Close contact: ≥15 min at ≤2 m, or during AGPs, between HCWs and the non-
isolated COVID-19 patient |
Not reported | ≤2 m for ≥15 min or during AGP |
| Bays 2020 | Not defined | Not reported | Not specified |
| Bi 2020 |
Close contacts were identified as those who lived in the same apartment,
shared a meal, travelled, or socially interacted with an index case 2 days before symptom onset. |
Casual contacts (eg, other clinic patients) and some
close contacts (eg, nurses) who wore a mask during exposure were not included in this group. |
Not specified |
| Blaisdell 2020 | Not defined | Not reported | 1 week |
| Böhmer 2020 | High risk if they had cumulative face-to-face contact with a patient with
laboratory-confirmed SARS-CoV-2 infection for at least 15 min, had direct contact with secretions or body fluids of a patient with confirmed COVID-19, or, in the case of health-care workers, had worked within 2 m of a patient with confirmed COVID-19 without PPE |
All other contacts were classified as low-risk contacts. | Face-to-face for at least 15 minutes, direct contact without
PPE |
| Boscolo-Rizzo 2020 | Not defined | Not reported | Not reported |
| Brown 2020 | Not defined | Not reported | Mean in-class time = 50 minutes |
| Burke 2020 | Either at least 10 minutes spent within 6 feet of the patient with confirmed
COVID-19 (e.g., in a waiting room) or having spent time in the same airspace (e.g., the same examination room) for 0–2 hours after the confirmed COVID-19 patient. |
Not reported | Within 6 feet for at least 10 minutes |
| Canova 2020 | Not defined | Not reported | 5 HCWs: >30 minutes
5 HCWs: >15–30 mins 6 HCWs: 5–15 mins 5 HCWs: ≤5 mins |
| Cariani 2020 | Not defined | Not reported | Not reported |
| Charlotte 2020 | Not defined | Not reported | 2-hours |
| Chaw 2020 |
Close contact: Any person living in the same household as a confirmed case-
patient or someone who had been within 1 m of a confirmed case-patient in an enclosed space for >15 minutes |
Not reported | Within 1m for >15 mins |
| Chen 2020 | Close contact: All passengers were regarded as close contacts | Not reported | Flight duration 5 hours approx |
| Chen 2020a |
Close contacts are persons who have had close contact with re-positive patients
without effective protection with masks, such as living and working together |
Not reported | Not specified |
| Chen 2020b | Not defined | Not reported | Not specified |
| Chu 2020 |
Community contact: Any close contact (being within 6 feet of the case-patient)
for a prolonged time (>10 minutes); being an office co-worker of the case-patient with close contact of any duration; contact with infectious secretions from the case-patient; or sharing a healthcare waiting room or area during the same time and up to 2 hours after the case-patient was present. |
Healthcare contact: Face-to-face interaction between
healthcare personnel (HCP) and the case-patient without wearing the full PPE that was recommended at the time of the investigation or potential contact with the case-patient’s secretions by HCP without wearing full PPE. |
>10 mins to 2 hours |
| Chen 2020c | Not defined | Not reported | Not reported |
| Cheng 2020 | Close contact was a person who did not wear appropriate PPE while having
face-to-face contact with a confirmed case for more than 15 minutes during the investigation period. A contact was listed as a household contact if he or she lived in the same household with the index case. Those listed as family contacts were family members not living in the same household. For health care settings, medical staff, hospital workers, and other patients in the same setting were included; close contact was defined by contacting an index case within 2 m without appropriate PPE and without a minimal requirement of exposure time |
Those listed as family contacts were family members
not living in the same household. |
Within 2 m without PPE, face-to-face contact for >15
minutes |
| Chu 2020a | Not defined | Not reported | Stayed ≥1 night in the household during case’s infectious
period |
| Contejean 2020 | Close contact: Distance <2 meters for >10 minutes was defined as close contact | Not reported | <2 metres for >10 minutes |
| COVID-19 National Emergency Response Center 2020 | Close contact (or high risk exposure)” was being within 2 meters of a COVID-19
case |
Daily contact (or low risk exposure) was defined as
having proximity with a person who was a confirmed COVID-19 case, without having had close contact. |
Not reported |
| Danis 2020 | All children and teachers who were in the same class as the symptomatic pediatric
case were considered as high risk contacts and were isolated at home. Moderate/high risk: Person who had prolonged (> 15 min) direct face-to-face contact within 1 m with a confirmed case, shared the same hospital room, lived in the same household or shared any leisure or professional activity in close proximity with a confirmed case, or travelled together with a COVID-19 case in any kind of conveyance, without appropriate individual protection equipment. |
Low risk: Person who had a close (within 1 m) but
short (< 15 min) contact with a confirmed case, or a distant (> 1 m) but prolonged contact in public settings, or any contact in private settings that does not match with the moderate/high risk of exposure criteria. Negligible risk: Person who had short (< 15 min) contact with a confirmed case in public settings such as in public transportation, restaurants and shops; healthcare personnel who treated a confirmed case while wearing appropriate PPE without any breach identified. |
4 days in chalet |
| Dattner 2020 | Not defined | Not reported | Not reported |
| de Brito 2020 | Close contact: Close and prolonged contact in the same room | Not reported | Not specified |
| Deng 2020 | Not defined | Not reported | Not reported |
| Desmet 2020 | Not defined | Not reported | Not reported |
| Dimcheff 2020 |
Close contact: Within 2 m or 6 feet) with an individual with confirmed COVID-19
for >15 minutes with the example being exposed to a family member at home who has had a positive COVID-19 nasal swab |
Not reported | Within 2m for >15 mins |
| Dong 2020 | Not defined | Not reported | Not reported |
| Doung-ngern 2020 |
High-risk if they were family members or lived in the same household as a
COVID-19 patient, if they were within a 1-meter distance of a COVID-19 patient longer than 15 minutes; if they were exposed to coughs, sneezes, or secretions of a COVID-19 patient and were not wearing protective gear, such as a mask; or if they were in the same closed environment within a 1-meter distance of a COVID- 19 patient longer than 15 minutes and were not wearing protective gear |
Not reported | <15 min vs >15 min, <1m vs >1m |
| Draper 2020 | Close contact was defined as anyone who had face-to-face contact with a
confirmed COVID-19 case for more than 15 minutes cumulatively or continuously (e.g. household setting or healthcare setting without appropriate use of personal protective equipment) or who was in the same room with an infectious case for more than 2 hours (e.g. school room, workplace) while a case was symptomatic or during the 24 hours preceding symptom onset. Aircraft close contacts included passengers seated in the same row as, or in the two rows in front of or behind, an infectious case. If the case was a crew member, the passengers in the area in which the crew member worked were classified as close contacts. Passengers disembarking from cruise ships with high incidence of COVID-19 were also classified as close contacts for surveillance purposes. |
Not reported | Not reported |
| Dub 2020 |
Close household contact, i.e. an individual sharing the main residence of the
secondary case |
A regular household contact, i.e. an individual who
would regularly host or stay in the same residence of a secondary case (step-sibling, divorced parent and new partner). Extended contact, i.e. an individual who would have frequent contact with the secondary case around and after the exposure, for example, grandparents who were involved in caring of the secondary case, according to parents’ reports. |
<2 meters for >10 minutes |
| Expert Taskforce 2020 | Close contact: Cabinmates of confirmed case-patients | Not reported | Not specified |
| Fateh-Moghadam 2020 | Contact of a COVID-19 case has been considered any person who has had
contact with a COVID-19 case within a time frame ranging from 48 hours before the onset of symptoms of the case to 14 days after the onset of symptoms |
Not reported | Not reported |
| Firestone 2020 |
Close contact: Being within 6 feet of a patient with laboratory-confirmed COVID-
19 infection for ≥15 minutes |
Not reported | Within 2m for >15 mins |
| Fontanet 2020 | Not defined | Not reported | Not reported |
| Fontanet 2020a | Not defined | Not reported | Not reported |
| Gan 2020 | Not defined | Not reported | Not reported |
| Ghinai 2020 | Not defined | Not reported | Not reported |
| Gong 2020 |
Close contact: Anyone who was closely in contact with a suspected, confirmed
and asymptomatic case without effective personal protection (classified protection according to the contact situation, including gloves, medical protective masks, protective face screens, isolation clothing, etc.) since onset of symptoms in the suspected case and confirmed case or the day asymptomatic case’s specimens were collected. The close contact included: (i) living, working, or studying in one house or classroom, (ii) diagnosing, treating, or visiting cases in hospital ward, (iii) being within short distance in the same vehicle, (iv) other situations assessed by the field investigators. |
Not reported | Not reported |
| Gu 2020 | Not defined | Not reported | 5 hrs, no natural ventilation or face masks;
distance between each other <0.5 m |
| Hamner 2020 | Close contact: Within 6 feet of infected case | Not reported | 2.5 hrs within 2 m |
| Han 2020 |
Close contact: Travel was defined as someone who was in close contact with
a confirmed case for over three hours as they traveled to another region aside from Region A. Close contact: meal was defined as someone who was in close contact with a confirmed case for over 30 minutes after having a meal together. |
A casual contact was defined as someone who spent
several minutes with a confirmed case within the same space without any mask on (or a person was established as a contact by an Epidemic intelligence Officer). |
30 mins to 3 hours |
| Heavey 2020 |
Close contact: Any individual who has had greaterthan 15 minutes face-to-face
(<2 meters distance*) contact with a case, in any setting. |
Casual contact: Any individual who has shared a closed
space with a case for less than two hours. |
Up to 2 hours in duration |
| Helsingen 2020 | Not defined | Not reported | Not reported |
| Hendrix 2020 | Not defined | Not reported | Not reported |
| Hirschman 2020 |
Close contact: Within 6 feet of an infected person for at least 15 minutes
starting from 2 days before illness onset. |
Not reported | "Hours" |
| Hobbs 2020 |
Close contact: Within 6 feet for ≥15 minutes) with a person with known COVID-
19, school or child care attendance, and family or community exposures ≤14 days before the SARS-CoV-2 test |
Not reported | Within 2 m for ≥15 minutes |
| Hoehl 2020 | Not defined | Not reported | Not reported |
| Hong 2020 | Anyone who ever came within 2 m of a diagnosed patient without the use of
effective personal protective equipment |
Not reported | 258 person-days |
| Hu 2020 |
Close contacts were defined as individuals who had close-proximity interactions
(within 1 meter) with clinically suspected and laboratory-confirmed SARS-CoV-2 cases, for the period from 2 days before, to 14 days after, the potential infector’s symptom onset. For those exposed to asymptomatic subjects, the contact period was from 2 days before, to 14 days after, a respiratory sample was taken for real-time RT-PCR testing. Close contacts included, but were not limited to, household contacts (i.e., household members regularly living with the case), relatives (i.e., family members who had close contacts with the case but did not live with the case), social contacts (i.e., a work colleague or classmate), and other close contacts (i.e., caregivers and patients in the same ward, persons sharing a vehicle, and those providing a service in public places, such as restaurants or movie theatres) |
Not reported | Not reported |
| Hua 2020 | Not defined | Not reported | |
| Huang 2020 | Close contacts quarantined at home or hospital | Not reported | Not reported |
| Huang 2020a | Not defined | Not reported | Not reported |
| Islam 2020 | Close contact was defined as individuals who were closely linked by contact
tracing and were considered a close contact group provided that no PPE was worn having direct face to face contacts. |
Household contacts were defined as individuals who
lived and were sharing the same room and same apartment in the same household. Family contacts were those who are the members of the same family but not living in the same household. |
Face-to-face |
| Jia 2020 | A
close contact was defined as a person who did not take effective protection
against a suspected or confirmed case 2 d before the onset of symptoms or an asymptomatic infected person 2 d before sampling. |
Not reported | Not reported |
| Jiang 2020 |
Close contacts: Lived with the patients and individuals who had contact with
the patients within 1 meter without wearing proper personal protection. Ct value ≥40 was considered negative. The maximum likelihood phylogenetic tree of the complete genomes was conducted by using RAxML software with 1000 bootstrap replicates, employing the general time-reversible nucleotide substitution mode |
Not reported | 1 m |
| Jing 2020 | A
close contact was defined as an individual who had unprotected close
contact (within 1 m) with a confirmed case within 2 days before their symptom onset or sample collection. Individuals who were linked by contact tracing were considered a close contact group |
Not reported | Not reported |
| Jing 2020a | Not defined | Not reported | Not reported |
| Jones 2020 |
Close contacts were defined by analysis of video footage for player interactions
and microtechnology (GPS) data for proximity analysis. |
Not reported | Within 1 m, face-to-face for ≥3 secs |
| Kang 2020 | Not defined | Not reported | Not reported |
| Kant 2020 | Not defined | Not reported | Not reported |
| Kawasuji 2020 | Not defined | Not reported | Not reported |
| Khanh 2020 |
Close contact: <2 m distance for >15 minutes. Successfully traced passengers
and crew members were interviewed by use of a standard questionnaire, tested for SARS-CoV-2 |
Not reported | <2 m distance for >15 minutes. |
| Kim 2020 | Not defined | Household contact: Occurring at least 1 day after but
within 14 days from the last point of exposure. |
2 days during the presymptomatic period and 1 day during
the symptomatic period of the index case. |
| Kim 2020a | Not defined | Not reported | 2 hrs to 4 days |
| Kim 2020b |
Contact was defined as presence in the same room with COVID-19 confirmed
patients, or in the same outpatient clinic or examination room, 30 minutes before and after COVID-19 confirmed patients. Within 2 m of confirmed patients (via CCTV) |
Not reported | Within 2 m of confirmed patients for 30 mins |
| Kumar 2020 | Not defined | Not reported | Not reported |
| Kuwelker 2020 | Not defined | Household members were defined as individuals who
resided in the same household as the index case. |
Not reported |
| Kwok 2020 |
Close contacts referred to anyone who: (i) provided care to the case (including
a family member or healthcare worker) or had other close physical contact; or (ii) stayed at the same place (including household members or visitors) while the case was ill. |
Not reported | Not reported |
| Ladhani 2020 | Not defined | Not reported | Not reported |
| Ladhani 2020a | Not defined | Not reported | Not reported |
| Laws 2020 | Not defined | Not reported | Unclear |
| Laxminarayan 2020 | High-risk contacts had close social contact or direct physical contact with index
cases without protective measures High-risk travel exposures—defined as close proximity to an infected individual in a shared conveyance for ≥6 hours |
Low-risk contacts were in the proximity of index cases
but did not meet criteria for high-risk exposure |
Not reported |
| Lee 2020 | Not defined: Frequent close contact | Not reported | >1 m |
| Lee 2020a | Close contact (household contact) | Not reported | Mean contact period was calculated to be 7.7 days. |
| Lewis 2020 | Not defined | Household contacts were defined as all persons living
in the same household as the primary patient. |
Not reported |
| Li 2020 | Not defined | Not reported | Unclear |
| Li 2020a | Not defined | Not reported | Not reported |
| Li 2020b |
Close contact was defined as an act of sharing a meal, party, vehicle or living
room with a confirmed or latently infected patient within 14 days. |
Not reported | Not reported |
| Li 2020c |
Close contacts were mainly those who have not take effective protection from
close contact with the suspected and confirmed cases 2 days before symptoms appeared, or the asymptomatic infected persons 2 days before the specimen collection. |
Not reported | Not reported |
| Li 2020d | Not defined | Not reported | Not reported |
| Liu 2020 | Not defined | Not reported | Unclear |
| Liu 2020a | Direct contact with patients with neo-coronary pneumonia (within 1 m) | Not reported | Within 1m for 2.5 hrs |
| Liu 2020b |
Close contacts were defined by the China Prevention and Control Scheme of
COVID-19. |
Not reported | 7.8 (95%CI: 7.0–8.7) close contacts per index case. |
| Liu 2020c | Not defined | Not reported | Not reported |
| López 2020 |
Close contact: Anyone who was within 6 feet of a person with COVID-19 for at
least 15 minutes ≤2 days before the patient’s symptom onset. |
Not reported | ≤1.83m of a person with COVID-19 for at least 15 minutes
≤2 days before the patient’s symptom onset |
| Lopez Bernal 2020 | Household contacts were defined as those living or spending significant time in
the same household. Household contacts, others with direct face to face contact and healthcare workers who had not worn recommended PPE |
Not reported | Not reported |
| Lucey 2020 |
Close contact: HCW or patient who spent more than 15 minutes face-to-face
within 2 metres of a confirmed case or patients who shared a multi-bedded room with a confirmed case for more than 2 hours. |
Not reported | Not reported |
| Luo 2020 | Unclear: The tour coach was with 49 seats was fully occupied with all windows
closed and the ventilation system on during the 2.5-hour trip. |
Not reported | 1 to 4.5m; up to 2.5 hours on a bus |
| Luo 2020a |
Close contacts: Anyone who has had contact, without effective protection
regardless of duration of exposure, with 1 or more persons with suspected or confirmed COVID-19 any time starting 2 days before onset of symptoms in persons with a suspected or confirmed case, or 2 days before sampling for laboratory testing of asymptomatic infected persons. |
Not reported | Not reported |
| Lyngse 2020 | Not defined | Not reported | Not reported |
| Ma 2020 | Not defined | Not reported | Longest contact time: 8 days
Shortest contact time: 0 days |
| Macartney 2020 |
Close contacts: Children or staff with face-to-face contact for at least 15 min,
or who shared a closed indoor space for at least 40 min with a case during their infectious period. |
Not reported | Face-to-face contact for at least 15 min, or who shared a
closed indoor space for at least 40 min |
| Malheiro 2020 |
Close contacts (high risk)were defined as individuals who have spent 15 min or
more in closeproximity (2 m or less) to, or in a closed space with, a case. |
Not reported | Not reported |
| Maltezou 2020 |
Close contact was defined as a contact of >15 minutes within a distance of <2 m
with a COVID-19 case. |
Household members were defined as persons living in
the same residence. |
>15 minutes within <2 m |
| Maltezou 2020a |
Close contact was defined as a contact of >15 minutes within a distance of <2
meters with a COVID-19 case |
Household contacts were defined as persons either
living in the same residence or having close contacts with a family member for >4 hours daily in the family residence. |
Household: >4 hours daily
Close contact: >15 minutes within <2 m |
| Mao 2020 | Not defined | Not reported | Not reported |
| Martinez-Fierro 2020 | Individual who has had closer than <6 feet for ≥15 min with people with
a positive diagnosis for COVID-19, whether they were symptomatic or asymptomatic according to the CDC definition |
Not reported | ≥15 min at a distance of <1.83m |
| Mponponsuo 2020 | An interaction of >15 minutes at a distance of <1 m | Not reported | >15 minutes at a distance of <1 m |
| Ng 2020 |
Close contacts were individuals who had contact for at least 30 min within a 2 m
distance from the index case. |
Work contacts were defined as individuals who came
into close contact with the index case at work, from 2 days before the onset of symptoms to isolation of the case, to account for pre-symptomatic transmission. Social contacts were defined as individuals who came into close contact with the index case, from 2 days before onset of symptoms to isolation of the case, through social activities. Transport contacts were excluded Lower risk contacts: Other contacts who were with the index case for 10–30 min within 2 m |
At least 30 min within a 2 m |
| Ning 2020 | Not defined | Not reported | Unclear |
| Njuguna 2020 | Not defined | Not reported | Unclear |
| Ogawa 2020 | Not defined | Not reported | Not reported |
| Paireau 2020 | Not defined | Not reported | Not reported |
| Park 2020 | Not defined | Not reported | Not reported |
| Park 2020a | High-risk contact (household contacts of COVID-19 patients, healthcare
personnel) |
Household contact was a person who lived in the
household of a COVID-19 patient and a nonhousehold contact was a person who did not reside in the same household as a confirmed COVID-19 patient. |
Not reported |
| Park 2020b | Not defined | Not reported | Not reported |
| Passarelli 2020 | Not defined | Not reported | Not reported |
| Patel 2020 | Not defined | Not reported | Not reported |
| Pavli 2020 |
Close contacts were defined as persons sitting within a distance of <2 m for >15 min,
including passengers seated two seats around the index case and all crew members and persons who had close contact with the index case. |
Not reported | <2 m for >15 min |
| Phiriyasart 2020 | Close contact was defined as a person who had at least one of these following
criteria : (i) a person who came into close (within 1 meter) contact with, or had a conversation with any patient for >5 minutes, or was coughed or sneezed on by any patient when he/she did not wear appropriate personal protective equipment (PPE), e.g. a face mask, (ii) a person who was in an enclosed space without proper ventilation, e.g. in the same air-conditioned bus/air-conditioned room as any patient , and was within one meter of any patient for >15 minutes without wearing appropriate PPE. High-risk close contact was defined as a close contact who was likely to contract the virus from any patient through exposure to respiratory secretions of any patient while not wearing PPE according to standard precautions. |
A low-risk close contact was defined as a close contact
who was less likely to contract the virus from any patient. This includes close contacts who have not met the definition for high-risk close contacts. |
Not reported |
| Poletti 2020 | Not defined | Not reported | Not reported |
| Pung 2020 |
Close contacts: People who spend a prolonged time within 2 m of a confirmed
case |
Other contacts: People who had some interactions
with the case. |
Unclear |
| Pung 2020a | Unclear: Close household contacts | Not reported | Unclear |
| Qian 2020 | Four categories of infected individuals were considered based on their
relationship: family members, family relatives, socially connected individuals, and socially non‐connected individuals |
Not reported | Not reported |
| Ravindran 2020 |
Close contact: Face-to-face contact for greater than 15 minutes cumulative in
the period extending from 48 hours before onset of symptoms in a confirmed case; or sharing of closed space with a confirmed case for a prolonged period of time in the period extending from 48 hours before onset of symptoms in a confirmed case. |
Not reported | Face-to-face contact for at least 15 min, or who shared a
closed indoor space for prolonged period 48 hrs before onset of symptoms |
| Razvi 2020 | Not defined | Not reported | Not reported |
| Rosenberg 2020 | Not defined | Not reported | |
| Roxby 2020 | Not defined | Not reported | Not reported |
| Sang 2020 | Not defined | Not reported | Not reported |
| Schumacher 2020 | Close contact: Approximately 30–90 seconds in close proximity (<1.5 m) of other
players |
Close social contacts (including sharing a car) | 30–90 seconds in close proximity (<1.5 m) |
| Schwierzeck 2020 | Not defined | Not reported | Not reported |
| Shah 2020 | Household contact was defined as contact sharing same residential address. | Not reported | Not reported |
| Shen 2020 |
Close contacts defined as individuals who had close, prolonged, and repeated
interactions with the 2 source cases (Cases 2 and 3). |
All other contacts are defined as casual contacts. | Not reported |
| Sikkema 2020 | Not defined | Not reported | Not reported |
| Son 2020 | Not defined | A contact was defined as anyone who was in contact
with a confirmed case from a day before the symptoms occurred, in a manner that offered the potential for transmission through respiratory droplets |
Not reported |
| Song 2020 | Unclear: shared the same bedroom, had dinner together | Not reported | Not reported |
| Speake 2020 | 2 rows in front and behind infectious passenger on an airplane | Not reported | Unclear |
| Stein-Zamir 2020 | Not defined | Not reported | Not reported |
| Sugano 2020 | Not defined | Not reported | Unclear |
| Sun 2020 | Not defined | Not reported | Not reported |
| Taylor 2020 | Not defined | Not reported | Unclear |
| Teherani 2020 | Household contacts (HCs) were defined as an adult ( 18 years) or a child (<18
years) who resided in the home with the SIC at the time of diagnosis. |
Not reported | Not reported |
| Thangaraj 2020 | Not defined | Not reported | Unclear |
| Torres 2020 | Not defined | Not reported | Unclear |
| Tshokey 2020 | Unclear: Close friends, roommates, flight seat partner, spouse or partner, cousin,
physician, tour driver |
Primary contacts: Individuals coming in some form of
contact with the confirmed cases such as conveyance in the same cars/flights, encounter in clinics, serving meals, or providing housekeeping services in hotels. Secondary contacts: Individuals coming in contact with the primary contacts |
Unclear |
| van der Hoek 2020 | Not defined | Not reported | |
| Wang 2020 | Not defined | Not reported | Unclear |
| Wang 2020a | Not defined | Not reported | Unclear |
| Wang 2020b | Close contact was defined as being within 1 m or 3 feet of the primary case, such
as eating around a table or sitting together watching TV. |
Not reported | Unclear |
| Wee 2020 | Not defined | Not reported | Within 2 m of the index case for a cumulative time of ≥15
minutes, or who had performed AGPs without appropriate PPE. |
| Wendt 2020 |
High-risk contacts: >15 min face-to-face contact, sitting in a row behind
physician for 45 mins, transfer in an ambulance (45-min drive). |
Not reported | >15 min face-to-face contact |
| Wolf 2020 | Not defined | Not reported | Not specified |
| Wong 2020 |
Contact case was defined as a patient or staff who stayed or worked in the same ward as the
index patient. Patients who shared the same cubicle with the index case were considered as ‘patient close contact’. Staff close contact: Staff who had contact within 2 m of the index case for a cumulative time of >15 min, or had performed AGPs, without ‘appropriate’ PPE. |
Casual contacts: All staff and patients who did not fulfill
the pre-defined criteria for close contacts. Casual/low-rosk contact: HCW wearing a facemask or respirator only and have prolonged close contact with a patient who was wearing a facemask, or HCW using all recommended PPE or HCW (not using all recommended PPE) who have brief interactions with a patient regardless of whether patient was wearing a facemask. Patient close contacts were quarantined into an AIIR (or quarantine camp if the patient was deemed clinically stable to be discharged from hospital) for 14 days. |
Within 2 m of the index case for a cumulative time of >15
min |
| Wood 2020 | Not defined | Not reported | Not reported |
| Wu 2020 |
Close contact: Been within 1 metre of a confirmed case, without effective PPE,
within the period since 5 days before the symptom onset in the index case or since 5 days before sampling if the index case was asymptomatic. |
Not reported | Within 1 metre of a confirmed case, without effective PPE |
| Wu 2020a | Household contacts were defined as person who spent at least 1 night in the
house after the symptom onset of the index patient. A household was defined as ≥2 people living together in the same indoor living space. A household index was the first person to introduce SARS-CoV-2 into the household. |
Not reported | At least 1 night |
| Xie 2020 |
Close contact: An individual who has not taken effective protection when in
proximity of suspected or confirmed cases 2 days before the onset of symptoms or 2 days before the collection of asymptomatic specimens. |
Not reported | Unclear |
| Xin 2020 | Close contacts were defined as persons who had a short‐range contact history
for 2 days before the onset of symptoms in COVID‐19‐suspected and ‐confirmed cases, or 2 days before the collection of samples from asymptomatic cases without taking effective protective measures, such as family members in the same house, direct caregivers, and medical staff who provided direct medical care, colleagues in the same office or workshop, etc. |
The effective contact duration for the close contacts
was defined as the contact days with index patients with confirmed COVID‐19, which was calculated as the last contact date minus the start contact date, and all dates were corresponding to the definition of close contacts |
The median effective contact duration with patients
with COVID‐19 was 4 (IQR: 1–6) days, with 57 (53.8%) experiencing effective contact between 3 and 11 days, and 9 (8.5%) with effective contact duration > 11 days |
| Yang 2020 | Close contacts: Uunprotected exposure. | Candidate contacts: Teachers and classmates | Not reported |
| Yau 2020 | Close unprotected contact with someone who has tested positive for COVID-19
in the last 14 days |
Not reported | Unclear |
| Ye 2020 | Not defined | Not reported | Not reported |
| Yoon 2020 |
Close contact was defined as a person who had face-to-face contact for >15
minutes or who had direct physical contact with the index case-patient. Persons who used the same shuttle bus were also considered to be close contacts. |
Not reported | Face-to-face contact for >15 minutes or direct physical
contact |
| Yousaf 2020 | Not defined | Not reported | Not reported |
| Yu 2020 |
Close contacts were defined as those who lived in the same household, shared
meals, traveled or had social interactions with a confirmed case two days before the onset of COVID-19 symptoms |
Not reported | Not reported |
| Yung 2020 | Not defined | Not reported | Not reported |
| Zhang 2020 | Not defined | Not reported | Not reported |
| Zhang 2020a |
Close contact: Refers to a person who had contact with index case without
using proper protection during 2 days before the index case was tested. |
Not reported | Not reported |
| Zhang 2020b | Not defined | Not reported | Not reported |
| Zhang 2020c |
Close contacts were individuals who lived with a PCR-confirmed case or
interacted with a case within 1 metre from the case without any personal protections. |
Not reported | Within 1m of case |
| Zhang 2020d | Not defined | Not reported | Not reported |
| Zhuang 2020 | Not defined | Not reported | Not reported |