Community transmission and viral load kinetics of the SARS-CoV-2 delta (B.1.617.2) variant in vaccinated and unvaccinated individuals in the UK: a prospective, longitudinal, cohort study.

BACKGROUND: The SARS-CoV-2 delta (B.1.617.2) variant is highly transmissible and spreading globally, including in populations with high vaccination rates. We aimed to investigate transmission and viral load kinetics in vaccinated and unvaccinated individuals with mild delta variant infection in the community. METHODS: Between Sept 13, 2020, and Sept 15, 2021, 602 community contacts (identified via the UK contract-tracing system) of 471 UK COVID-19 index cases were recruited to the Assessment of Transmission and Contagiousness of COVID-19 in Contacts cohort study and contributed 8145 upper respiratory tract samples from daily sampling for up to 20 days. Household and non-household exposed contacts aged 5 years or older were eligible for recruitment if they could provide informed consent and agree to self-swabbing of the upper respiratory tract. We analysed transmission risk by vaccination status for 231 contacts exposed to 162 epidemiologically linked delta variant-infected index cases. We compared viral load trajectories from fully vaccinated individuals with delta infection (n=29) with unvaccinated individuals with delta (n=16), alpha (B.1.1.7; n=39), and pre-alpha (n=49) infections. Primary outcomes for the epidemiological analysis were to assess the secondary attack rate (SAR) in household contacts stratified by contact vaccination status and the index cases' vaccination status. Primary outcomes for the viral load kinetics analysis were to detect differences in the peak viral load, viral growth rate, and viral decline rate between participants according to SARS-CoV-2 variant and vaccination status. FINDINGS: The SAR in household contacts exposed to the delta variant was 25% (95% CI 18-33) for fully vaccinated individuals compared with 38% (24-53) in unvaccinated individuals. The median time between second vaccine dose and study recruitment in fully vaccinated contacts was longer for infected individuals (median 101 days [IQR 74-120]) than for uninfected individuals (64 days [32-97], p=0·001). SAR among household contacts exposed to fully vaccinated index cases was similar to household contacts exposed to unvaccinated index cases (25% [95% CI 15-35] for vaccinated vs 23% [15-31] for unvaccinated). 12 (39%) of 31 infections in fully vaccinated household contacts arose from fully vaccinated epidemiologically linked index cases, further confirmed by genomic and virological analysis in three index case-contact pairs. Although peak viral load did not differ by vaccination status or variant type, it increased modestly with age (difference of 0·39 [95% credible interval -0·03 to 0·79] in peak log10 viral load per mL between those aged 10 years and 50 years). Fully vaccinated individuals with delta variant infection had a faster (posterior probability >0·84) mean rate of viral load decline (0·95 log10 copies per mL per day) than did unvaccinated individuals with pre-alpha (0·69), alpha (0·82), or delta (0·79) variant infections. Within individuals, faster viral load growth was correlated with higher peak viral load (correlation 0·42 [95% credible interval 0·13 to 0·65]) and slower decline (-0·44 [-0·67 to -0·18]). INTERPRETATION: Vaccination reduces the risk of delta variant infection and accelerates viral clearance. Nonetheless, fully vaccinated individuals with breakthrough infections have peak viral load similar to unvaccinated cases and can efficiently transmit infection in household settings, including to fully vaccinated contacts. Host-virus interactions early in infection may shape the entire viral trajectory. FUNDING: National Institute for Health Research.

Broadening symptom criteria improves early case identification in SARS-CoV-2 contacts.

BACKGROUND: The success of case isolation and contact tracing for the control of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission depends on the accuracy and speed of case identification. We assessed whether inclusion of additional symptoms alongside three canonical symptoms (CS), i.e. fever, cough and loss or change in smell or taste, could improve case definitions and accelerate case identification in SARS-CoV-2 contacts. METHODS: Two prospective longitudinal London (UK)-based cohorts of community SARS-CoV-2 contacts, recruited within 5 days of exposure, provided independent training and test datasets. Infected and uninfected contacts completed daily symptom diaries from the earliest possible time-points. Diagnostic information gained by adding symptoms to the CS was quantified using likelihood ratios and area under the receiver operating characteristic curve. Improvements in sensitivity and time to detection were compared with penalties in terms of specificity and number needed to test. RESULTS: Of 529 contacts within two cohorts, 164 (31%) developed PCR-confirmed infection and 365 (69%) remained uninfected. In the training dataset (n=168), 29% of infected contacts did not report the CS. Four symptoms (sore throat, muscle aches, headache and appetite loss) were identified as early-predictors (EP) which added diagnostic value to the CS. The broadened symptom criterion "≥1 of the CS, or ≥2 of the EP" identified PCR-positive contacts in the test dataset on average 2 days earlier after exposure (p=0.07) than "≥1 of the CS", with only modest reduction in specificity (5.7%). CONCLUSIONS: Broadening symptom criteria to include individuals with at least two of muscle aches, headache, appetite loss and sore throat identifies more infections and reduces time to detection, providing greater opportunities to prevent SARS-CoV-2 transmission.

Reliability of a retail food store survey and development of an accompanying retail scoring system to communicate survey findings and identify vendors for healthful food and marketing initiatives.

OBJECTIVE: To develop a retail grocery instrument with weighted scoring to be used as an indicator of the food environment. PARTICIPANTS/SETTING: Twenty six retail food stores in low-income areas in California. INTERVENTION: Observational. MAIN OUTCOME MEASURE(S): Inter-rater reliability for grocery store survey instrument. Description of store scoring methodology weighted to emphasize availability of healthful food. ANALYSIS: Type A intra-class correlation coefficients (ICC) with absolute agreement definition or a κ test for measures using ranges as categories. RESULTS: Measures of availability and price of fruits and vegetables performed well in reliability testing (κ = 0.681-0.800). Items for vegetable quality were better than for fruit (ICC 0.708 vs 0.528). Kappa scores indicated low to moderate agreement (0.372-0.674) on external store marketing measures and higher scores for internal store marketing. "Next to" the checkout counter was more reliable than "within 6 feet." Health departments using the store scoring system reported it as the most useful communication of neighborhood findings. CONCLUSIONS AND IMPLICATIONS: There was good reliability of the measures among the research pairs. The local store scores can show the need to bring in resources and to provide access to fruits and vegetables and other healthful food.

Using geographic information systems and local food store data in California's low-income neighborhoods to inform community initiatives and resources.

OBJECTIVES: We examined conditions in California low-income neighborhoods that affect obesity to inform program planning, nutrition education, community participation, investment of resources, and involvement of stakeholders. METHODS: Staff members in 18 local health departments were trained to use an online geographic information system (GIS) and conduct field surveys. GIS data were aggregated from 68 low-income neighborhoods of 1 or more census tracts. Data were collected in 2007 to 2009 from 473 grocery stores in 62 neighborhoods. RESULTS: Thirty-one percent of neighborhoods mapped had no supermarket within any of their census tract boundaries, but health department staff members estimated that 74.2% of residents had access to a large grocery store within 1 mile. Eighty-one percent of small markets sold produce, and 67.6% offered 4 or more types of fresh vegetables. CONCLUSIONS: Small markets and corner stores in California's low-income neighborhoods often have fresh produce available for sale. Stores providing healthy options in typically underserved areas can be part of community efforts to promote healthy eating behaviors.

Seizing the moment: California's opportunity to prevent nutrition-related health disparities in low-income Asian American population.

Asian Americans and Pacific Islanders (AAPI) have the fastest growing rate of overweight and obese children. Aggressive programs are urgently needed to prevent unhealthy acculturation-related changes in diet and physical activity and to promote the healthier aspects of traditional lifestyle habits. We conducted focus groups and key informant interviews to explore knowledge, attitudes, dietary practices, and physical activity levels among three low-income Asian American ethnic groups, Chinese, Vietnamese, and Hmong, in California. Content analysis was used to identify similarities and differences among the groups. Several common health beliefs clearly emerged. Participants noted the importance of fresh (not frozen) fruit and vegetable consumption and physical activity for general health. The concept of good health included having a harmonious family, balance, and mental and emotional stability. All groups also expressed the general belief that specific foods have hot or cold properties and are part of the Yin/Yang belief system common to Asian cultures. The lure of fast food, children's adoption of American eating habits, and long work hours were identified as barriers to a healthy, more traditional lifestyle. A California campaign for Asian Americans using multilevel strategies is recommended to counter the alarming rise of obesity among AAPI youth. Strategies directed to individual, community, and policy levels should emphasize maintenance of healthy traditional diets, informed selection of mainstream U.S. foods, and promotion of active lifestyles to prevent an impending burden from cancer and nutrition-related chronic diseases in AAPI populations.