Table 3. Risk of Bias.
| Study ID | Description of
methods and sufficient detail to replicate? |
Sample
sources clear? |
Analysis &
reporting appropriate? |
Is bias
dealt with? |
Results
applicable? |
Notes |
|---|---|---|---|---|---|---|
| Abdulrahman 2020 | Unclear | Yes | Yes | No | Yes | |
| Adamik 2020 | Unclear | Unclear | Yes | No | Unclear | |
| Afonso 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Agergaard 2020 | No | Yes | Yes | No | Yes | |
| Akaishi 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Angulo-Bazán 2020 | Yes | No | Yes | Unclear | Yes | |
| Armann 2020 | Unclear | Yes | Yes | No | Yes | |
| Arnedo-Pena 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Atherstone 2021 | No | No | Yes | Unclear | Yes | |
| Baettig 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Baker 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Bao 2020 | Unclear | Yes | Yes | No | Yes | |
| Basso 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Bays 2020 | Unclear | Yes | Yes | No | Yes | |
| Bender 2021 | Unclear | No | Yes | Unclear | Unclear | Evidence was obtained from
a single outbreak and might not be applicable to other settings. Recall bias |
| Bernardes-Souza 2021 | Yes | Yes | Yes | Unclear | Yes | Recall bias |
| Bhatt 2022 | Yes | Yes | Yes | Unclear | Yes | |
| Bi 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Bi 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Bistaraki 2021 | Yes | Unclear | Yes | Unclear | Yes | |
| Bjorkman 2021 | Unclear | Yes | Yes | Unclear | Yes | |
| Blaisdell 2020 | Yes | No | Yes | Unclear | Yes | |
| Böhmer 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Boscolo-Rizzo 2020 | Unclear | Yes | Yes | No | Yes | |
| Brown 2020 | Yes | Yes | Yes | Unclear | Unclear | |
| Burke 2020 | Unclear | No | Yes | No | Yes | |
| Calvani 2021 | Yes | Yes | Yes | Unclear | Yes | Recall bias |
| Canova 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Carazo 2021 | Yes | Unclear | Yes | Unclear | Yes | |
| Cariani 2020 | Unclear | Yes | Unclear | Unclear | Yes | |
| Carvalho 2022 | Unclear | Yes | Yes | Unclear | Yes | |
| Cerami 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Charlotte 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Chaw 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Chen 2020 | Unclear | Unclear | Yes | No | Unclear | |
| Chen 2020a | Unclear | Yes | Yes | Unclear | Yes | |
| Chen 2020b | Yes | Yes | Yes | Unclear | Yes | |
| Chen 2020c | Unclear | No | Yes | No | Yes | |
| Cheng 2020 | Yes | No | Yes | Unclear | Yes | |
| Chu 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Chu 2020a | Unclear | Unclear | Unclear | No | Yes | |
| Contejean 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Cordery 2021 | Yes | Yes | Yes | Unclear | Yes | |
|
COVID-19 National
Emergency Response Center 2020 |
Unclear | No | Yes | No | Yes | |
| Craxford 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Danis 2020 | Yes | Yes | Yes | No | Yes | |
| Dattner 2020 | Yes | Yes | Yes | Unclear | Yes | |
| de Brito 2020 | Yes | Yes | Unclear | Unclear | Yes | |
| Deng 2020 | Unclear | No | Unclear | Unclear | Unclear | |
| Desmet 2020 | Yes | Yes | Yes | No | Unclear | |
| Dimcheff 2020 | Yes | Unclear | Yes | Unclear | Unclear | |
| Dong 2020 | Unclear | No | Unclear | No | Yes | |
| Doung-ngern 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Draper 2020 | Yes | Yes | Yes | No | Yes | |
| Dub 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Expert Taskforce 2020 | Unclear | Unclear | Yes | Unclear | Unclear | |
| Farronato 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Fateh-Moghadam 2020 | Unclear | No | Yes | No | Yes | |
| Firestone 2020 | Unclear | Unclear | Yes | Unclear | Yes | |
| Fontanet 2021 | Yes | Yes | Yes | No | Yes | |
| Galow 2021 | No | Yes | Yes | Unclear | Unclear | |
| Gamboa Moreno 2021 | Unclear | Unclear | Unclear | Unclear | Unclear | no explanation of sample
taking |
| Gan 2020 | Unclear | Unclear | Unclear | Unclear | Unclear | |
| Gaskell 2021 | Unclear | Yes | Yes | Unclear | Yes | |
| Ge 2021 | Yes | Yes | Yes | Yes | Yes | Conducted sensitivity
analyses restricting the study population to household and nonhousehold contacts |
| Ghinai 2020 | Unclear | Unclear | Unclear | Unclear | Unclear | |
| Gold 2021 | Unclear | Yes | Yes | Unclear | Yes | Method used to identify close
contacts not clearly described |
| Gomaa 2021 | Unclear | Yes | Yes | Unclear | Yes | |
| Gonçalves 2021 | Yes | Yes | Yes | Unclear | Yes | Recall bias |
| Gong 2020 | Yes | Yes | Unclear | Unclear | Unclear | |
| Gu 2020 | Unclear | Unclear | Unclear | No | Unclear | |
| Hamner 2020 | Unclear | Unclear | Yes | No | Yes | |
| Han 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Hast 2022 | Yes | Yes | Yes | Unclear | Yes | |
| Heavey 2020 | Unclear | No | Yes | No | Yes | |
| Helsingen 2020 | Yes | Yes | Yes | Yes | Yes | |
| Hendrix 2020 | Yes | Yes | Yes | No | Yes | |
| Hirschman 2020 | Unclear | Unclear | Unclear | No | Yes | |
| Hobbs 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Hoehl 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Hong 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Hsu 2021 | Unclear | Unclear | Yes | Unclear | Yes | Asymptomatic patients could
have been missed |
| Hu 2020 | Unclear | No | Yes | No | Yes | |
| Hu 2020 | Yes | Unclear | Yes | Unclear | Yes | |
| Hu 2021 | Yes | Yes | Unclear | Unclear | Yes | Criteria for categorizing times
into 0-1.5, 1.5-2.5, and >2.5 hrs unclear |
| Hua 2020 | Yes | Unclear | Yes | Unclear | Yes | |
| Huang 2020 | Unclear | Unclear | Yes | No | Unclear | |
| Huang 2020a | Unclear | Unclear | Yes | Unclear | Unclear | |
| Huang 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Islam 2020 | Yes | No | Yes | No | Yes | |
| Jashaninejad 2021 | Yes | Unclear | Yes | Unclear | Yes | |
| Jeewandara 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Jia 2020 | Unclear | Unclear | Yes | No | Unclear | |
| Jiang 2020 | Yes | Yes | Unclear | No | Yes | |
| Jing 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Jing 2020a | Unclear | Yes | Unclear | Unclear | Unclear | |
| Jones 2020 | Unclear | Yes | Yes | Unclear | Unclear | |
| Jordan 2022 | Yes | Yes | Yes | Unclear | Yes | |
| Kang 2020 | Unclear | Unclear | Unclear | Unclear | Unclear | |
| Kant 2020 | Unclear | Yes | Unclear | No | Unclear | |
| Karumanagoundar 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Katlama 2022 | Yes | Yes | Unclear | Unclear | Yes | No formal statistical analysis
was planned |
| Kawasuji 2020 | Unclear | Yes | Unclear | Unclear | Unclear | |
| Khanh 2020 | Yes | Yes | Yes | No | Yes | |
| Kim 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Kim 2020a | Unclear | Yes | Yes | No | Unclear | |
| Kim 2020b | Yes | Yes | Yes | No | Yes | |
| Kim 2021 | N/A | Yes | Yes | N/A | Yes | |
| Kitahara 2022 | Unclear | Unclear | Yes | Unclear | Yes | |
| Klompas 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Kolodziej 2022 | Yes | Yes | Yes | Yes | Yes | Conducted sensitivity analyses
excluding households with a possible other primary case than the defined index case |
| Koureas 2021 | Unclear | Unclear | Yes | Unclear | Yes | Identification of the index
case was not possible in 10/40 households since two or more household members were simultaneously found to be positive. |
| Kumar 2020 | Unclear | Yes | Unclear | No | Unclear | |
| Kuwelker 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Kuwelker 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Kwok 2020 | Unclear | Unclear | Yes | Unclear | Unclear | |
| Ladhani 2020 | No | Unclear | Unclear | No | Yes | |
| Ladhani 2020a | Unclear | Unclear | Yes | Unclear | Yes | |
| Laws 2020 | Unclear | Unclear | Yes | Unclear | Yes | |
| Laws 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Laxminarayan 2020 | Yes | No | Yes | No | Yes | |
| Lee 2020 | Unclear | Unclear | Yes | Unclear | Unclear | |
| Lee 2020a | Unclear | No | Yes | No | Yes | |
| Lewis 2020 | Yes | Yes | Yes | No | Yes | |
| Li 2020 | Unclear | Yes | Unclear | No | Unclear | |
| Li 2020a | Unclear | Unclear | Unclear | Unclear | Unclear | |
| Li 2020b | Unclear | Yes | Unclear | Unclear | Unclear | |
| Li 2020c | Unclear | No | Unclear | Unclear | Unclear | |
| Li 2020d | Yes | Yes | Yes | No | Yes | |
| Li 2021a | Yes | Unclear | Yes | Unclear | Yes | |
| Li 2021b | Yes | Yes | Yes | Unclear | Yes | |
| Lin 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Liu 2020 | Unclear | Unclear | Unclear | No | Yes | |
| Liu 2020a | Yes | Yes | Yes | Unclear | Unclear | |
| Liu 2020b | Unclear | Yes | Yes | Unclear | Yes | |
| Liu 2020c | Unclear | Unclear | Unclear | No | Unclear | |
| Liu 2021 | Yes | Yes | Yes | Unclear | Yes | |
| López 2020 | Unclear | Unclear | Yes | Unclear | Yes | |
| López 2021 | Yes | Unclear | Yes | Unclear | Yes | |
| Lopez Bernal 2020 | Yes | Unclear | Yes | No | Yes | |
| Lopez Bernal 2022 | Yes | Unclear | Yes | Unclear | Yes | |
| Lucey 2020 | Unclear | Yes | Yes | No | Yes | |
| Luo 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Luo 2020a | Unclear | Yes | Yes | Yes | Yes | They use multiple imputation
to minimise inferential bias, and they discuss recall bias, selection bias and regression to the mean. |
| Lyngse 2020 | Yes | Unclear | Yes | Yes | Yes | They investigate bias within
their data and discuss this fairly fully |
| Ma 2020 | Unclear | Unclear | Unclear | Unclear | Unclear | |
| Macartney 2020 | Yes | Unclear | Yes | Unclear | Yes | |
| Malheiro 2020 | Yes | Unclear | Yes | Unclear | Yes | |
| Maltezou 2020 | Unclear | Unclear | Unclear | Unclear | Yes | |
| Maltezou 2020a | Unclear | Unclear | Unclear | No | Yes | |
| Mao 2020 | Unclear | Unclear | Yes | No | Unclear | |
| Martínez-Baz 2022 | Yes | Yes | Yes | Unclear | Yes | |
| Martinez-Fierro 2020 | Unclear | Yes | Yes | No | Yes | |
| McLean 2022 | Yes | Yes | Yes | Unclear | Yes | |
| Mercado-Reyes 2022 | Yes | Yes | Yes | Unclear | Yes | |
| Metlay 2021 | Unclear | Unclear | Yes | Unclear | Yes | |
| Meylan 2021 | Yes | Unclear | Yes | Unclear | Yes | |
| Miller 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Montecucco 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Mponponsuo 2020 | Unclear | Yes | Yes | Yes | Yes | Recall bias was minimized
by examining multiple data sources for both index cases and exposed persons |
| Musa 2021 | Yes | Unclear | Yes | Unclear | Yes | |
| Ng 2020 | Unclear | Yes | Yes | Yes | Yes | Authors looked at differences
that could have led to bias |
| Ng 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Ning 2020 | Unclear | Unclear | Unclear | Unclear | Unclear | |
| Njuguna 2020 | Unclear | Unclear | Yes | Unclear | Yes | |
| Nsekuye 2021 | Unclear | Yes | Yes | Unclear | Yes | |
| Ogata 2021 | Unclear | Unclear | Yes | Unclear | Yes | |
| Ogawa 2020 | Unclear | Unclear | Yes | No | Yes | |
| Paireau 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Pang 2022 | Unclear | Unclear | Yes | Unclear | Yes | |
| Park 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Park 2020a | Unclear | No | Yes | No | Yes | |
| Park 2020b | Unclear | Yes | Yes | No | Unclear | |
| Passarelli 2020 | Unclear | No | Unclear | Unclear | Yes | |
| Patel 2020 | Yes | Yes | Yes | Unclear | Unclear | |
| Pavli 2020 | Unclear | Yes | Yes | No | Yes | |
| Petersen 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Pett 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Phiriyasart 2020 | Yes | Yes | Yes | No | Yes | |
| Poletti 2020 | Unclear | Yes | Yes | Yes | Unclear | |
| Powell 2022 | Yes | Yes | Yes | Unclear | Yes | |
| Pung 2020 | Yes | Unclear | Yes | Unclear | Yes | |
| Pung 2020a | Unclear | No | Unclear | Unclear | Unclear | |
| Qian 2020 | Unclear | Unclear | Unclear | No | Unclear | |
| Ratovoson 2022 | Yes | Yes | Yes | Unclear | Yes | |
| Ravindran 2020 | Unclear | Unclear | Unclear | Unclear | Unclear | |
| Razvi 2020 | Unclear | Yes | Yes | No | Yes | |
| Reukers 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Robles Pellitero 2021 | Yes | No | Yes | Unclear | Yes | Recall bias |
| Rosenberg 2020 | Yes | Yes | Yes | No | Yes | |
| Roxby 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Sakamoto 2022 | Unclear | Yes | Yes | Unclear | Yes | Use of protection is
unclear; testing only done is participants were symptomatic |
| Sang 2020 | Unclear | Yes | Unclear | No | Unclear | |
| Sarti 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Satter 2022 | Yes | Yes | Yes | Unclear | Yes | |
| Schoeps 2021 | Yes | Yes | Yes | Yes | Yes | Advised DPHAs to report
consecutive index cases over at least a 4-week period or longer, thus reducing the chance of systematic under- or over-reporting |
| Schumacher 2020 | Unclear | Yes | Unclear | Unclear | Yes | |
| Schwierzeck 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Semakula 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Shah 2020 | Unclear | No | Unclear | No | Yes | |
| Shah 2021 | Unclear | No | Yes | Unclear | Yes | |
| Shen 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Sikkema 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Son 2020 | Unclear | Unclear | Yes | No | Yes | |
| Song 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Sordo 2022 | Yes | No | Yes | Unclear | Yes | |
| Soriano-Arandes 2021 | Yes | Yes | Yes | Unclear | Yes | To avoid selection bias in case
recruitment, paediatricians recorded all positive cases seen in daily practice |
| Speake 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Stein-Zamir 2020 | Yes | Unclear | Yes | No | Yes | |
| Stich 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Sugano 2020 | Unclear | Unclear | Yes | Unclear | Yes | |
| Sun 2020 | Unclear | Unclear | Unclear | Unclear | Unclear | |
| Sun 2021 | Unclear | Yes | Yes | Unclear | Yes | |
| Sundar 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Tadesse 2021 | Unclear | Yes | Yes | Unclear | Yes | |
| Tanaka 2021 | Unclear | Yes | Yes | Unclear | Yes | |
| Tanaka 2022 | Unclear | Yes | Yes | Unclear | Yes | Used a convenience
recruitment strategy. |
| Taylor 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Teherani 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Thangaraj 2020 | Unclear | Yes | Yes | Unclear | Unclear | |
| Torres 2020 | Yes | Unclear | Yes | Unclear | Yes | |
| Tsang 2022 | Yes | Unclear | Yes | Unclear | Yes | |
| Tshokey 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Tsushita 2022 | Yes | Unclear | Yes | Unclear | Yes | |
| van der Hoek 2020 | Unclear | Yes | Yes | No | Yes | |
| Vičar 2021 | Yes | Unclear | Yes | Unclear | Yes | |
| Wang 2020 | Unclear | Yes | Unclear | Unclear | Yes | |
| Wang 2020a | Yes | Unclear | Yes | Unclear | Yes | |
| Wang 2020b | Yes | Yes | Yes | No | Yes | |
| Wee 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Wendt 2020 | Yes | Yes | Yes | Unclear | Yes | |
| White 2022a | Yes | Unclear | Yes | Unclear | Yes | |
| White 2022b | Yes | Unclear | Yes | Unclear | Yes | |
| Wiens 2021 | Yes | Yes | Yes | Unclear | Yes | For households with more
than 10 people, only the first- degree relatives of the head of household were eligible for study inclusion. |
| Wolf 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Wong 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Wood 2020 | Unclear | No | Yes | Unclear | Yes | |
| Wu 2020 | Yes | Unclear | Yes | Unclear | Yes | |
| Wu 2020a | Yes | Unclear | Yes | Unclear | Yes | |
| Wu 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Xie 2020 | Unclear | Yes | Yes | Unclear | Yes | |
| Xie 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Xin 2020 | Yes | No | Yes | No | Yes | |
| Yang 2020 | Unclear | Yes | Unclear | Unclear | Yes | |
| Yau 2020 | Unclear | Yes | Unclear | Unclear | Unclear | |
| Ye 2020 | Unclear | Unclear | Unclear | Unclear | Unclear | |
| Yi 2021 | Unclear | Yes | Yes | Unclear | Yes | |
| Yoon 2020 | Yes | Yes | Yes | Unclear | Yes | |
| Yousaf 2020 | Unclear | Yes | Unclear | Unclear | Unclear | |
| Yu 2020 | Yes | No | Yes | No | Yes | |
| Yung 2020 | Unclear | Yes | Yes | No | Yes | |
| Zhang 2020 | Unclear | Unclear | Unclear | No | Unclear | |
| Zhang 2020a | Yes | Unclear | Yes | Unclear | Unclear | |
| Zhang 2020b | Unclear | Yes | Unclear | Unclear | Yes | |
| Zhang 2020c | Unclear | Unclear | Unclear | Unclear | Unclear | |
| Zhang 2020d | Unclear | Yes | Unclear | Unclear | Unclear | |
| Zhang 2021 | Yes | Yes | Yes | Unclear | Yes | |
| Zhuang 2020 | Unclear | No | Yes | No | Unclear |