Risk of Severe Acute Respiratory Syndrome Coronavirus 2 Acquisition Is Associated With Individual Exposure but Not Community-Level Transmission
Authors: Friedman-Klabanoff DeAnna J , Fitzpatrick Meagan C , Deming Meagan E , Agrawal Vaidehi , Sitar Sandra , Schaafsma Torin , Brown Elizabeth , Neuzil Kathleen M , Barnabas Ruanne V , Laufer Miriam K ,   Hydroxychloroquine COVID-19 Postexposure Prophylaxis Study Team, Dull Peter , Miller Scott , Pham Thy , Arroyave Luisa , Berz Jonathan , Buitron Pablo , Camuso Michael , Cardoso Leticia , Cruz Ricardo , Dedier Julien , Dennaoui Husam , Goldman Anna , Greenstein Cheryl , Henault Lori , Johnson Terrell , Kimball Sarah , Martinez Carlie , Martinez Erin , Ng Crystal , Paarz William , Ogunneye Qausarat , Paasche-Orlow Lev , Rogers Margot , Salerno Kathleen , Smithline Michael , Streed Carl , Verma Nisha , Waite Katherine , Hosek Sybil , Balthazar Christopher , Jarris Ann , Greene Leslie Anna , Buist Diana , Aldana Sandra India , Alsaloum Marissa , Anastasiou Elle , Cardozo Rodrigo Arce , Badiei Beita , Bakirova Kamilla , Bakirova Zulfiya , Barnes Caroline , Bedi Sukhleen K , Beggs Dia B , Bendik Stefanie E , Cao Meng , Chang Michelle , Chen Shirley , Cheng Anna , Chong Stella K , Coates Jane , Conderino Sarah , Connery Jacqueline , Connolly Megan , Contreras Aira L , Dreier Matthew S , Duan Emily , Hidalgo Eveline Teresa , Fadzan Maja , Fagan Samantha N , Fried Jamie , Gago Juan , Gakou Nadia , Gill Emily , Gujral Akash , Hao Xiaolei , Hughes Christina , James Robert T , Kim Sean , Krieger Penina , Landon Susan N , Liang Alice Li Juan , Lopez Priscilla M , Mamistvalova Lia , Schwartz Mark D , McQuay Saydee , Miao Wei (William) , Mohaimin Sadia , Gabriela Kaicy , Nguyen-Stone Naranjo, Krissy , Peltekci Ashley , Peña Andrea , Perdomo Katherine , Pompeii Mary Lou , Quintana Lindsey , Reynolds Amanda J , Pitts Robert A , Rodriguez Andrea , Sasankan Prabhu , Sharma Sneha R , Shire Amy , Sota Stela , Spoer Ben R , Springer Bethany , Stadelman Jay , Wysota Christina N , Yang Jackie , Yepez Myriam , Cram Danielle , Eustace Stephen , Mandziuk Kathleen , Massaro Michael , Mullenix Colleen , Reichard Toze , Towner Tiara , Abbott Mark , Asiago-Reddy Elizabeth , Baxter Kristen , Caiello Kate , Endy Timothy , Geneva Ivayla , Greco Peter , Harausz Elizabeth , Klick Michelle , Mehlek Patrick , Miller Christopher , Reale Melissa , Ripich Kianna , Shaw Andrea , Terrillion Keely , Thomas Stephen , Anibaba Mueenah , Atkinson Evan , Blyth Michelle , Campbell Mary Beth , Carsch Lillianna , Ganguly Ashita , Gupta Sarina , Larkin Heather , Hall Jake , Huntwork John , Huntwork Margaret , McConville Mariel , McDougal April , Numbi Florice , Ntambwe Cedrick , Palomares Michelle , Plaxico Demetrius , Rady Hamada , Ribando Maria , Sauter Sydney , Triggs Daniel , Upadhyay Neha , Schmidt Norine , Watson Shannon , Zheng Crystal , Arias Rubi , Bhimani Azra J , Blair Cherie , Cambou Catie , Cayabyab Meilani , Corona Rafael , Escobedo Danielle , Furukawa Daisuke , Gonzalez Amanda , Karpf Heather , Kofron Ryan , Largaespada Karla , Lopez Nancy , Mansky Hannah , Martin-Blais Rachel , Petreuse Antonia , Shin Christina , Tran Tran T , Weldon Ameila , Were Gabriela , Agrawal Vaidehi , Billington Melissa , Birkhold Megan , Boyce Colleen , Cloeren Marianne , Palacios Carlo Foppiano , Friedman-Klabanoff DeAnna , Kwon Alyson , LeBuhn Hanna , Liu Esther , Lu Meredith , McDiarmid Melissa , Myers Melissa , Pa’ahana-Brown Faith , Poley Marian , Shrestha Biraj , Wilkerson Gentry , Alidina Nathan , Arnold Samuel , Bauer Marie , Baugh Jennifer , Bayer Cara , Bole Medhavi , Brandstetter Elizabeth , Braun Alyssa , Brown Clare E , Brown Maxwell , Bulterys Michelle , Castor Jared , Dematteis Maianna , Doan Ivy , Drummond Mark , Feutz Erika , Galagan Sean , Hamilton Daphne , Hauge Kirsten , Hay Elsa , Hladik Florian , Hou Xuanlin , Houston Doug , Humphreys Madelaine , Hussein Abir , Ikuma Matthew , Issema Rodal , Johnson Rachel , Kirk Mary , Knauer Jack , Kuntz Steven R , Lawton Savannah , Letterer Rebecca , Lingappa Elina , Lingappa Jairam R , Liou Caroline H , Lund Katie , Maddox Toni , Mathur Anya , Metter Mari , McClellan Lindsey , Montoya Deidra , Moreno Jessica C , Pandey Gregory Morlin, Urvashi , Pepper Gregory , Pettit Alicia , Pholsena Thepthara , Popp Griffin , Purcell Jeff , Quame-Amaglo Justice , Sampoleo Reigran , Sanger Elliott , Seymour Matthew , Shercliffe Alexander , Somani Shabir , Stewart Jenell C , Tamakole Selorm , Taub Jina M , Thuesmunn Zoe , Tungara Amena , Valinetz Ethan , Varon Dana L , Vazquez Vianey , Vo Bao-Chau , Wanga Valentine , Waters Chloe D , Wei Yulun , Welsh Meagan , Wicklander Katie , Wood Brian R , Young Grant , Young Zohdi , Zhao Lucy , Zimmermann Azaad , Brown Deborah J , Davenport Nathaniel , Gambito Omar 
Published: January 2022

Abstract

Background
Transmission rates after exposure to a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)–positive individual within households and healthcare settings varies significantly between studies. Variability in the extent of exposure and community SARS-CoV-2 incidence may contribute to differences in observed rates.

Methods
We examined risk factors for SARS-CoV-2 infection in a randomized controlled trial of hydroxychloroquine as postexposure prophylaxis. Study procedures included standardized questionnaires at enrollment and daily self-collection of midturbinate swabs for SARS-CoV-2 polymerase chain reaction testing. County-level incidence was modeled using federally sourced data. Relative risks and 95% confidence intervals were calculated using modified Poisson regression.

Results
Eighty-six of 567 (15.2%) household/social contacts and 12 of 122 (9.8%) healthcare worker contacts acquired SARS-CoV-2 infection. Exposure to 2 suspected index cases (vs 1) significantly increased risk for both household/social contacts (relative risk [RR], 1.86) and healthcare workers (RR, 8.18). Increased contact time also increased risk for healthcare workers (3–12 hours: RR, 7.82, &gt;12 hours: RR, 11.81, vs ≤2 hours), but not for household/social contacts. County incidence did not impact risk.

Conclusions
In our study, increased exposure to SARS-CoV-2 within household or healthcare settings led to higher risk of infection, but elevated community incidence did not. This reinforces the importance of interventions to decrease transmission in close contact settings.