The added effect of non-pharmaceutical interventions and lifestyle behaviors on vaccine effectiveness against severe COVID-19 in Chile: A matched case-double control study.

BACKGROUND: World Health Organization approved vaccines have demonstrated relatively high protection against moderate to severe COVID-19. Prospective vaccine effectiveness (VE) designs with first-hand data and population-based controls are nevertheless rare. Neighborhood compared to hospitalized controls, may differ in compliance to non-pharmacuetical interventions (NPI) compliance, which may influence VE results in real-world settings. We aimed to determine VE against COVID-19 intensive-care-unit (ICU) admission using hospital and community-matched controls in a prospective design. METHODS: We conducted a multicenter, observational study of matched cases and controls (1:3) in adults ≧18 years of age from May to July 2021. For each case, a hospital control and two community controls were matched by age, gender, and hospital admission date or neighborhood of residence. Conditional logistic regression models were built, including interaction terms between NPIs, lifestyle behaviors, and vaccination status; the model's ß coefficients represent the added effect these terms had on COVID-19 VE. RESULTS: Cases and controls differed in several factors including education level, obesity prevalence, and behaviors such as compliance with routine vaccinations, use of facemasks, and routine handwashing. VE was 98·2% for full primary vaccination and 85·6% for partial vaccination when compared to community controls, and somewhat lower, albeit not significantly, compared to hospital controls. A significant added effect to vaccination in reducing COVID-19 ICU admission was regular facemask use and VE was higher among individuals non-compliant with the national vaccine program, and/or tonroutine medical visits during the prior year. CONCLUSION: VE against COVID-19 ICU admission in this stringent prospective case-double control study reached 98% two weeks after full primary vaccination, confirming the high effectiveness provided by earlier studies. Face mask use and hand washing were independent protective factors, the former adding additional benefit to VE. VE was significantly higher in subjects with increased risk behaviors.

Contribution of Two-Dose Vaccination Toward the Reduction of COVID-19 Cases, ICU Hospitalizations and Deaths in Chile Assessed Through Explanatory Generalized Additive Models for Location, Scale, and Shape

Objectives To assess the impact of the initial two-dose-schedule mass vaccination campaign in Chile toward reducing adverse epidemiological outcomes due to SARS-CoV-2 infection. Methods Publicly available epidemiological data ranging from 3 February 2021 to 30 September 2021 were used to construct GAMLSS models that explain the beneficial effect of up to two doses of vaccination on the following COVID-19-related outcomes: new cases per day, daily active cases, daily occupied ICU beds and daily deaths. Results Administered first and second vaccine doses, and the statistical interaction between the two, are strong, statistically significant predictors for COVID-19-related new cases per day (R2 = 0.847), daily active cases (R2 = 0.903), ICU hospitalizations (R2 = 0.767), and deaths (R2 = 0.827). Conclusion Our models stress the importance of completing vaccination schedules to reduce the adverse outcomes during the pandemic. Future work will continue to assess the influence of vaccines, including booster doses, as the pandemic progresses, and new variants emerge. Policy Implications This work highlights the importance of attaining full (two-dose) vaccination status and reinforces the notion that a second dose provides increased non-additive protection. The trends we observed may also support the inclusion of booster doses in vaccination plans. These insights could contribute to guiding other countries in their vaccination campaigns.

Sensitivity and Specificity of Patient-Reported Clinical Manifestations to Diagnose COVID-19 in Adults from a National Database in Chile: A Cross-Sectional Study.

(1) Background: The diagnosis of COVID-19 is frequently made on the basis of a suggestive clinical history and the detection of SARS-CoV-2 RNA in respiratory secretions. However, the diagnostic accuracy of clinical features is unknown. (2) Objective: To assess the diagnostic accuracy of patient-reported clinical manifestations to identify cases of COVID-19. (3) Methodology: Cross-sectional study using data from a national registry in Chile. Infection by SARS-CoV-2 was confirmed using RT-PCR in all cases. Anonymised information regarding demographic characteristics and clinical features were assessed using sensitivity, specificity, and diagnostic odds ratios. A multivariable logistic regression model was constructed to combine epidemiological risk factors and clinical features. (4) Results: A total of 2,187,962 observations were available for analyses. Male participants had a mean age of 43.1 ± 17.5 years. The most common complaints within the study were headache (39%), myalgia (32.7%), cough (31.6%), and sore throat (25.7%). The most sensitive features of disease were headache, myalgia, and cough, and the most specific were anosmia and dysgeusia/ageusia. A multivariable model showed a fair diagnostic accuracy, with a ROC AUC of 0.744 (95% CI 0.743-0.746). (5) Discussion: No single clinical feature was able to fully confirm or exclude an infection by SARS-CoV-2. The combination of several demographic and clinical factors had a fair diagnostic accuracy in identifying patients with the disease. This model can help clinicians tailor the probability of COVID-19 and select diagnostic tests appropriate to their setting.

[Diagnostic properties of case definitions of suspected COVID-19 in Chile, 2020Características diagnósticas das definições de caso suspeito de COVID-19 no Chile, 2020]. / Propiedades diagnósticas de las definiciones de caso sospechoso de COVID-19 en Chile, 2020.

OBJECTIVE: Compare the diagnostic properties of five case definitions of suspected COVID-19 that were used or proposed in Chile during the first eight months of the pandemic. METHODS: An analysis was done of the diagnostic properties (sensitivity, specificity, and positive and negative predictive values) of three case definitions of suspected COVID-19 used in Chile between March and October 2020, as well as two alternative proposed definitions. The sample was 2,019 people with known results for the polymerase chain reaction (PCR) test for SARS-CoV-2. Stepwise logistic regression was used to develop criterion 5, optimizing sensitivity and specificity values. Multifactor logistic regression was used to explore the association between demographic variables, symptoms and signs, and PCR positivity. Different positivity scenarios were analyzed and ROC curves were compared. RESULTS: The presence of anosmia (OR = 8.00; CI95%: 5.34-11.99), fever (OR = 2.15; CI95%: 1.28-3.59), and having been in close contact with a person sick with COVID-19 (OR = 2.89; CI95%: 2.16-3.87) were associated with a positive PCR result. According to the analysis of the ROC curve, criterion 5 had the highest capacity for discrimination, although there were no significant differences with the other four criteria. CONCLUSIONS: Criterion 5-based on anosmia, close contact with people with COVID-19, and fever as sufficient unique elements-was the most sensitive in identifying suspected cases of COVID-19, a key aspect in controlling the spread of the pandemic.

OBJETIVO: Comparar as características diagnósticas de cinco critérios das definições de caso suspeito de COVID-19 usados ou propostos no Chile nos oito primeiros meses de pandemia. MÉTODOS: Foram avaliadas as características diagnósticas (sensibilidade, especificidade e valores preditivos positivo e negativo) de três critérios das definições de caso suspeito de COVID-19 usados no Chile entre março e outubro de 2020 e de duas alternativas propostas para definição de caso. A amostra do estudo consistiu 2 019 pessoas com resultados conhecidos no exame de reação em cadeia da polimerase (PCR) para SARS-CoV-2. Para elaborar o critério 5, uma regressão logística com método stepwise foi realizada otimizando os valores de sensibilidade e especificidade. A associação entre variáveis demográficas, sintomas e sinais e resultado positivo no exame de PCR foi testada em um modelo de regressão logística multifatorial. Situações diferentes de resultado positivo foram testadas com uma análise comparativa das curvas ROC. RESULTADOS: Presença de anosmia (OR 8,00; IC95% 5,34­11,99), febre (OR 2,15; IC95% 1,28­3,59) e contato próximo anterior com uma pessoa com COVID-19 (OR 2,89; IC95% 2,16­3,87) foram associados a um resultado positivo no exame de PCR. De acordo com a análise das curvas ROC, o critério 5 demonstrou maior capacidade discriminatória, apesar de não existir diferença significativa com os outros quatro critérios. CONCLUSÃO: O critério 5 ­ presença de anosmia, febre e contato próximo com uma pessoa com COVID-19 como elementos únicos e suficientes ­ demonstrou maior sensibilidade para identificar casos suspeitos de COVID-19, o que é fundamental para controlar a disseminação da pandemia.

A cross sectional study found differential risks for COVID-19 seropositivity amongst health care professionals in Chile.

OBJECTIVE: Health care workers (HCWs) are at increased risk for SARS-CoV-2 infection, however not all face the same risk. We aimed to determine IgG/IgM prevalence and risk factors associated with seropositivity in Chilean HCWs. STUDY DESIGN AND SETTING: This was a nationwide, cross-sectional study including a questionnaire and COVID-19 lateral flow IgG/IgM antibody testing. All HCWs in the Chilean public health care system were invited to participate following the country's first wave. RESULTS: IgG/IgM positivity in 85,529 HCWs was 7.2%, ranging from 1.6% to 12.4% between regions. Additionally, 9.7% HCWs reported a positive PCR of which 47% were seropositive. Overall, 10,863 (12.7%) HCWs were PCR and/or IgG/IgM positive. Factors independently associated with increased odds ratios (ORs) for seropositivity were: working in a hospital, night shifts, contact with Covid-19, using public transport, male gender, age>45, BMI ≥30, and reporting ≥2 symptoms. Stress and/or mental health disorder and smoking were associated with decreased ORs. These factors remained significant when including PCR positive cases in the model. CONCLUSIONS: HCWs in the hospital were at highest risk for COVID-19, and several independent risk factors for seropositivity and/or PCR positivity were identified.