A network meta-analysis of secondary attack rates of COVID-19 in different contact environments

Abstract

As the corona virus disease 2019 (COVID-19) pandemic continues around the world, understanding the transmission characteristics of COVID-19 is vital for prevention and control. We conducted the first study aiming to estimate and compare the relative risk of secondary attack rates (SARs) of COVID-19 in different contact environments. Until 26 July 2021, epidemiological studies and cluster epidemic reports of COVID-19 were retrieved from SCI, Embase, PubMed, CNKI, Wanfang and CBM in English and Chinese, respectively. Relative risks (RRs) were estimated in pairwise comparisons of SARs between different contact environments using the frequentist NMA framework, and the ranking of risks in these environments was calculated using the surface under the cumulative ranking curve (SUCRA). Subgroup analysis was performed by regions. Thirty-two studies with 68 260 participants were identified. Compared with meal or gathering, transportation (RR 10.55, 95% confidence interval (CI) 1.43-77.85), medical care (RR 11.68,) and work or study places (RR 10.15,) had lower risk ratios for SARs. Overall, the SUCRA rankings from the highest to the lowest were household (95.3%), meal or gathering (81.4%), public places (58.9%), daily conversation (50.1%), transportation (30.8%), medical care (18.2%) and work or study places (15.3%). Household SARs were significantly higher than other environments in the subgroup of mainland China and sensitive analysis without small sample studies (<100). In light of the risks, stratified personal protection and public health measures need to be in place accordingly, so as close contacts categorising and management.

Estimating the risk reduction of isolation on COVID-19 non-household transmission and severe/critical illness in non-immune individuals: September to November 2021

“…A systematic search identified 7 meta-analyses of the wild-type SARs [6][7][8][9][10][11][12] (see Supplemental Appendix). Delta SARs in six types of settings were estimated after applying this procedure to the mean SARs across these meta-analyses: households (mean SAR=32.59%), social gatherings (mean SAR=11.69%), casual close contacts (mean SAR=3.05%), work/study places (mean SAR=2.89%), healthcare (mean SAR=2.96%), and travel/transportation (mean SAR=4.40%) (Table S1).…”

“…In other words, this data is ideal for our purposes because it captures the SARs of non-immune index cases in different types of non-household settings. Therefore, the Delta SAR in a given type of non-household setting ( SAR Delta ) can be estimated by multiplying the wild-type SARs ( SAR wt ) by a correction factor ( CF Delta =1.97) to account for the increased transmissibility of Delta over the wild-type, which is about 97% more transmissible based on a global analysis of reproduction numbers [5]: A systematic search identified 7 meta-analyses of the wild-type SARs [6-12] (see Supplemental Appendix). Delta SARs in six types of settings were estimated after applying this procedure to the mean SARs across these meta-analyses: households (mean SAR=32.59%), social gatherings (mean SAR=11.69%), casual close contacts (mean SAR=3.05%), work/study places (mean SAR=2.89%), healthcare (mean SAR=2.96%), and travel/transportation (mean SAR=4.40%) (Table S1).…”

Evaluating the number of unvaccinated people needed to exclude to prevent SARS-CoV-2 transmissions

“…13 citations were identified from the search. 1 meta-analysis 13 was identified in our pilot study. 3 The meta-analytic estimates of the SARs were extracted from the 7 meta-analyses meeting the inclusion criteria.…”

“…3 The meta-analytic estimates of the SARs were extracted from the 7 meta-analyses meeting the inclusion criteria. [13][14][15][16][17][18][19] All analyses were conducted in R. 20 The NNE model makes four assumptions. First, we assume the Delta variant correction factor (𝐶𝐹 𝐷𝑒𝑙𝑡𝑎 =1.97) is accurate.…”

“…3 The meta-analytic estimates of the SARs were extracted from the 7 meta-analyses meeting the inclusion criteria. 13-19 All analyses were conducted in R. 20…”