Instruct: Identify the main category of the given Medrxiv paper based on its title.
Query: Sexual risk among pregnant women at risk of HIV infection in Cape Town, South Africa: What does alcohol have to do with it?
Understanding the pathways leading to socioeconomic inequalities in HIV testing uptake in 18 sub-Saharan African countries: a mediation analysis
Tobacco 21: Retailer Perceptions, Experiences, and Challenges Before and After a New Minimum Legal Sales Age Law in Maryland
Theoretical derivation and clinical validation of the resolution limit of human eye to spherical lens change：A Self-controlled Study
Analysis and visualization of epidemics on the timescale of burden: derivation and application of Epidemic Resistance Lines (ERLs) to COVID-19 outbreaks in the US
Immunity status in patients with periprosthetic knee joint infection
Transparency and reporting characteristics of COVID-19 randomized controlled trials.
Coadministration of AYUSH 64 as an adjunct to Standard of Care in mild and moderate COVID-19: A randomised, controlled, multicentric clinical trial
Is It Really Musculoskeletal Pain? Differential diagnosis and screening for referral in paediatric musculoskeletal disorders: a scoping review protocol
Do school closures reduce community transmission of COVID-19? A systematic review of observational studies
Longitudinal experiences and impact of the COVID-19 pandemic among people with past or current eating disorders in Sweden
Contributions of occupation characteristics and educational attainment to racial/ethnic inequities in COVID-19 mortality
The relative impact of vaccination momentum on COVID-19 rates of death in the USA in 2020/2021. The forgotten role of population wellness.
Characterising the persistence of RT-PCR positivity and incidence in a community survey of SARS-CoV-2
How often do cancer researchers make their data and code available and what factors are associated with sharing?
Evidence of long-lasting humoral and cellular immunity against SARS-CoV-2 even in elderly COVID-19 convalescents showing a mild to moderate disease progression
Convergent abnormalities of β-amyloid deposition, glucose metabolism, and fMRI activity in the dorsal precuneus in subjective cognitive decline
UK Health Care Workers' Experiences of Major System Change in Elective Surgery during the COVID-19 Pandemic: Reflections on Rapid Service Adaptation
Comparing the genetic and environmental architecture of blood count, blood biochemistry and urine biochemistry biological ages with machine learning
Comparing survival in urinary tract cancer patients with various second primary malignancies: A population-based study
Targeted transcutaneous cervical spinal cord stimulation promotes upper limb recovery in spinal cord and peripheral nerve injury
COVID Outcome Prediction in the Emergency Department (COPE)
What We Learned from COVID-19: From endotheliitis to treatment
Proteome-wide Mendelian randomization identifies causal links between blood proteins and severe COVID-19
Leg ulcers are associated with an increased risk of Sickle eye disease in Lagos.
Electronic Computer-Based Model of Combined Ventilation Using a New Medical Device