The question is: estimate the risk difference of Covid-19 infection for subjects randomized to the Hydroxychloroquine arm compared to subjects randomized to the placebo arm.Am I right to begin to find the CI?So 49/414 and 58/407 and then subtract those numbers to arrive at a negative number?

b. Covid-19 (or suspected Covid-19) infection C. Hydroxychloroquine d. Exposure to Covid-19 3. A July 2020 article in the New England Journal of Medicine reports the results of a randomized trial designed to assess the efficacy 1 point of Hydroxychloroquine in preventing Covid-19 infection in persons exposed to others with Covid-19. As per the article's abstract: BACKGROUND Coronavirus disease 2019 (Covid-19) occurs after exposure to severe acute respira- tory syndrome coronavirus 2 (SARS-CoV-2). For persons who are exposed, the standard of care is observation and quarantine. Whether hydroxychloroquine can prevent symptomatic infection after SARS-CoV-2 exposure is unknown. METHODS We conducted a randomized, double-blind, placebo-controlled trial across the United States and parts of Canada testing hydroxychloroquine as postexposure pro- phylaxis. We enrolled adults who had household or occupational exposure to some- one with confirmed Covid-19 at a distance of less than 6 ft for more than 10 minutes while wearing neither a face mask nor an eye shield (high-risk exposure) or while wearing a face mask but no eye shield (moderate-risk exposure). Within 4 days after exposure, we randomly assigned participants to receive either placebo or hydroxychloroquine (800 mg once, followed by 600 mg in 6 to 8 hours, then 600 mg daily for 4 additional days). The primary outcome was the incidence of either labo- ratory-confirmed Covid-19 or illness compatible with Covid-19 within 14 days. The findings of the study are detailed in the following table (just a heads up: we will learn about p-values and their interpretation later in this course!) Table 2. Outcomes of Hydroxychloroquine Therapy for Postexposure Prophylaxis against Covid-19.# Hydroxychloroquine Placebo Outcome (N=414) (N=407) P Value number (percent) Confirmed or probable Covid-19 49 (11.8) 58 (14.3 ) 0.35 0.82 Laboratory-confirmed diagnosis 11 (2.7) 9 ( 2.2 ) Symptoms compatible with Covid-19 48 (11.6) 55 (13.5) 0.46 59 (14.5) 0.84 All new symptoms 57 (13.8 ) 0.99 Any hospitalization 1 (0.2) 1 (0.2) 0 Death ence (difference in proportions) of Covid-19 (or suspected Covid-19) infection for subjects randomized to domized to the placebo arm. (Hydroxychloroquine - placebo). 549 O