Comparison of the Risk of Hospitalization and Severe Disease Among Co-circulating Severe Acute Respiratory Syndrome Coronavirus 2 Variants.

BACKGROUND: We compare the risk of coronavirus disease 2019 (COVID-19) outcomes among co-circulating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants between January 2021 and May 2022 in Navarra, Spain. METHODS: We compared the frequency of hospitalization and severe disease (intensive care unit admission or death) due to COVID-19 among the co-circulating variants. Variants analyzed were nonvariants of concern (non-VOCs), Alpha, Delta, Omicron BA.1, and Omicron BA.2. Logistic regression models were used to estimate adjusted odds ratio (aOR). RESULTS: The Alpha variant had a higher risk of hospitalization (aOR, 1.86 [95 confidence interval {CI}, 1.282.71]) and severe disease (aOR, 2.40 [95 CI, 1.314.40]) than non-VOCs. The Delta variant did not show a significantly different risk of hospitalization (aOR, 0.73 [95 CI, .401.30]) and severe disease (aOR, 3.04 [95 CI, .5716.22]) compared to the Alpha variant. The Omicron BA.1 significantly reduced both risks relative to the Delta variant (aORs, 0.28 [95 CI, .16.47] and 0.23 [95 CI, .12.46], respectively). The Omicron BA.2 reduced the risk of hospitalization compared to BA.1 (aOR, 0.52 [95 CI, .29.95]). CONCLUSIONS: The Alpha and Delta variants showed an increased risk of hospitalization and severe disease, which decreased considerably with the Omicron BA.1 and BA.2. Surveillance of variants can lead to important differences in severity.

Patient satisfaction with HIV care service in Spain: results from a cross-sectional patient survey.

Understanding patient satisfaction with healthcare services can help identify patients' unmet needs and increase treatment adherence. This study aimed to evaluate the satisfaction of people living with HIV with overall HIV care service in Navarra, Spain, using a cross-sectional survey. The survey included a patient-reported experience measure (PREMs) consisting of five statements, and participants were also asked to rate the overall care they receive from the HIV service. Chi-square tests were used to detect differences between groups for statements and Kruskal-Wallis rank test was used to detect differences in ranking of the HIV service. The 395 participants gave the HIV service a mean score of 9.3 points out of 10 (standard deviation 1.1). Only 15 (4%) gave a score of under 8 out of 10, and adherence to antiretroviral therapy was associated with higher ranking of the service. Agreement for all five statements ranged from 80% to 96%. Those without stable housing, with mental health problems, and unemployed felt less supported to manage their HIV. These results highlight the need to regularly assess patient satisfaction with the HIV care and that care should account for social and economic factors that could influence health.

Risk reduction of hospitalisation and severe disease in vaccinated COVID-19 cases during the SARS-CoV-2 variant Omicron BA.1-predominant period, Navarre, Spain, January to March 2022.

BackgroundAs COVID-19 vaccine effectiveness against SARS-CoV-2 infection was lower for cases of the Omicron vs the Delta variant, understanding the effect of vaccination in reducing risk of hospitalisation and severe disease among COVID-19 cases is crucial.AimTo evaluate risk reduction of hospitalisation and severe disease in vaccinated COVID-19 cases during the Omicron BA.1-predominant period in Navarre, Spain.MethodsA case-to-case comparison included COVID-19 epidemiological surveillance data in adults ≥ 18 years from 3 January-20 March 2022. COVID-19 vaccination status was compared between hospitalised and non-hospitalised cases, and between severe (intensive care unit admission or death) and non-severe cases using logistic regression models.ResultsAmong 58,952 COVID-19 cases, 565 (1.0%) were hospitalised and 156 (0.3%) were severe. The risk of hospitalisation was reduced within the first 6 months after full COVID-19 vaccination (complete primary series) (adjusted odds ratio (aOR): 0.06; 95% CI: 0.04-0.09) and after 6 months (aOR: 0.16; 95% CI: 0.12-0.21; pcomparison < 0.001), as well as after a booster dose (aOR: 0.06: 95% CI: 0.04-0.07). Similarly, the risk of severe disease was reduced (aOR: 0.13, 0.18, and 0.06, respectively). Compared with cases fully vaccinated 6 months or more before a positive test, those who had received a booster dose had lower risk of hospitalisation (aOR: 0.38; 95% CI: 0.28-0.52) and severe disease (aOR: 0.38; 95% CI: 0.21-0.68).ConclusionsFull COVID-19 vaccination greatly reduced the risk of hospitalisation and severe outcomes in COVID-19 cases with the Omicron variant, and a booster dose improved this effect in people aged over 65 years.

Vaccine effectiveness against COVID-19 hospitalisation in adults (≥ 20 years) during Alpha- and Delta-dominant circulation: I-MOVE-COVID-19 and VEBIS SARI VE networks, Europe, 2021.

IntroductionTwo large multicentre European hospital networks have estimated vaccine effectiveness (VE) against COVID-19 since 2021.AimWe aimed to measure VE against PCR-confirmed SARS-CoV-2 in hospitalised severe acute respiratory illness (SARI) patients ≥ 20 years, combining data from these networks during Alpha (March-June)- and Delta (June-December)-dominant periods, 2021.MethodsForty-six participating hospitals across 14 countries follow a similar generic protocol using the test-negative case-control design. We defined complete primary series vaccination (PSV) as two doses of a two-dose or one of a single-dose vaccine ≥ 14 days before onset.ResultsWe included 1,087 cases (538 controls) and 1,669 cases (1,442 controls) in the Alpha- and Delta-dominant periods, respectively. During the Alpha period, VE against hospitalisation with SARS-CoV2 for complete Comirnaty PSV was 85% (95% CI: 69-92) overall and 75% (95% CI: 42-90) in those aged ≥ 80 years. During the Delta period, among SARI patients ≥ 20 years with symptom onset ≥ 150 days from last PSV dose, VE for complete Comirnaty PSV was 54% (95% CI: 18-74). Among those receiving Comirnaty PSV and mRNA booster (any product) ≥ 150 days after last PSV dose, VE was 91% (95% CI: 57-98). In time-since-vaccination analysis, complete all-product PSV VE was > 90% in those with their last dose < 90 days before onset; ≥ 70% in those 90-179 days before onset.ConclusionsOur results from this EU multi-country hospital setting showed that VE for complete PSV alone was higher in the Alpha- than the Delta-dominant period, and addition of a first booster dose during the latter period increased VE to over 90%.

Vaccine effectiveness against COVID-19 hospitalisation in adults (≥ 20 years) during Omicron-dominant circulation: I-MOVE-COVID-19 and VEBIS SARI VE networks, Europe, 2021 to 2022.

IntroductionThe I-MOVE-COVID-19 and VEBIS hospital networks have been measuring COVID-19 vaccine effectiveness (VE) in participating European countries since early 2021.AimWe aimed to measure VE against PCR-confirmed SARS-CoV-2 in patients ≥ 20 years hospitalised with severe acute respiratory infection (SARI) from December 2021 to July 2022 (Omicron-dominant period).MethodsIn both networks, 46 hospitals (13 countries) follow a similar test-negative case-control protocol. We defined complete primary series vaccination (PSV) and first booster dose vaccination as last dose of either vaccine received ≥ 14 days before symptom onset (stratifying first booster into received < 150 and ≥ 150 days after last PSV dose). We measured VE overall, by vaccine category/product, age group and time since first mRNA booster dose, adjusting by site as a fixed effect, and by swab date, age, sex, and presence/absence of at least one commonly collected chronic condition.ResultsWe included 2,779 cases and 2,362 controls. The VE of all vaccine products combined against hospitalisation for laboratory-confirmed SARS-CoV-2 was 43% (95% CI: 29-54) for complete PSV (with last dose received ≥ 150 days before onset), while it was 59% (95% CI: 51-66) after addition of one booster dose. The VE was 85% (95% CI: 78-89), 70% (95% CI: 61-77) and 36% (95% CI: 17-51) for those with onset 14-59 days, 60-119 days and 120-179 days after booster vaccination, respectively.ConclusionsOur results suggest that, during the Omicron period, observed VE against SARI hospitalisation improved with first mRNA booster dose, particularly for those having symptom onset < 120 days after first booster dose.

Effectiveness of influenza vaccination in preventing influenza in primary care, Navarre, Spain, 2021/22.

Compared with individuals unvaccinated in the current and three previous influenza seasons, in 2021/22, influenza vaccine effectiveness at primary care level was 37% (95% CI: 16 to 52) for current season vaccination, regardless of previous doses, and 35% (95% CI: -3 to 45) for only previous seasons vaccination. Against influenza A(H3N2), estimates were 39% (95% CI: 16 to 55) and 24% (95% CI: -8 to 47) suggesting moderate effectiveness of current season vaccination and possible remaining effect of prior vaccinations.

Seroprevalence of antibodies against SARS-CoV-2 and risk of COVID-19 in Navarre, Spain, May to July 2022.

In Navarre, Spain, in May 2022, the seroprevalence of anti-nucleocapsid (N) and anti-spike (S) antibodies of SARS-CoV-2 was 58.9% and 92.7%, respectively. The incidence of confirmed COVID-19 thereafter through July was lower in people with anti-N antibodies (adjusted odds ratio (aOR) = 0.08; 95% confidence interval (CI): 0.05-0.13) but not with anti-S antibodies (aOR = 1.06; 95% CI: 0.47-2.38). Hybrid immunity, including anti-N antibodies induced by natural exposure to SARS-CoV-2, seems essential in preventing Omicron COVID-19 cases.

Effect of influenza vaccination in patients with asthma.

BACKGROUND: Although annual influenza vaccination is recommended for persons with asthma, its effectiveness in this patient population is not well described. We evaluated the effect of influenza vaccination in the current and previous seasons in preventing influenza among people with asthma. METHODS: Using population health data from the Navarre region of Spain for the 2015/16 to 2019/20 influenza seasons, we conducted a test-negative case-control study to assess the effect of influenza vaccination in the current and 5 previous seasons. From patients presenting to hospitals and primary health care centres with influenza-like illness who underwent testing for influenza, we estimated the effects of influenza vaccination among patients with asthma overall and between those presenting as inpatients or outpatients, as well as between patients with and without asthma. RESULTS: Of 1032 patients who had asthma and were tested, we confirmed that 421 had influenza and the remaining 611 were test-negative controls. We found that the average effect of influenza vaccination was 43% (adjusted odds ratio [OR] 0.57, 95% confidence interval [CI] 0.40 to 0.80) for current-season vaccination regardless of previous doses, and 38% (adjusted OR 0.62, 95% CI 0.39 to 0.96) for vaccination in previous seasons only. Effects were similar for outpatients and inpatients. Among patients with asthma and confirmed influenza, current-season vaccination did not reduce the odds of hospital admission (adjusted OR 1.05, 95% CI 0.51 to 2.18). Influenza vaccination effects were similar for patients with and without asthma. INTERPRETATION: We estimated that, on average, current or previous influenza vaccination of people with asthma prevented almost half of influenza cases. These results support recommendations that people with asthma receive influenza vaccination.

Quality of life in people living with HIV in Romania and Spain.

BACKGROUND: Health-related quality of life (HRQoL) is a crucial component in assessing and addressing the unmet needs of people, especially those with chronic illnesses such as HIV. The aim of the study was to examine and compare the health-related quality of life of people living with HIV in Romania and Spain, compared to the general populations of each country. METHODS: A cross-sectional survey was conducted among adults (≥ 18 years) attending for HIV care in Romania and Spain from October 2019 to March 2020. The survey included two validated HRQoL instruments: a generic instrument, EQ-5D-5L, and an HIV-specific instrument, PozQoL, and questions on socio-demographics, HIV-related characteristics, physical and mental health conditions, and substance use. Multivariable linear regression was used to determine factors associated with HRQoL. RESULTS: 570 people living with HIV responded (170 in Romania and 400 in Spain). The median age was 31 (18-67) in Romania and 52 (19-83) in Spain. Anxiety/depression symptoms were frequently reported by people with HIV (Romania: 50% vs 30% in the Romanian population; Spain: 38% vs 15% in Spanish population). Spain reported higher mean EQ-5Dutility scores than Romania (0.88 and 0.85, respectively) but identical PozQoL scores (3.5, on a scale of 0-5). In both countries, health concerns were highlighted as a key issue for people with HIV. In multivariable analysis, two factors were consistently associated with worse HRQoL in people with HIV: bad or very bad self-rated health status and presence of a mental health condition. In Romania, being gay/bisexual and being disabled/unemployed were associated with worse HRQoL. Whereas in Spain, older age and financial insecurity were significant predictors. CONCLUSIONS: Our results indicated a good HRQoL for people living with HIV in Romania and Spain; however, worse HRQoL profiles were characterized by health concerns, poor self-rated health status, and the presence of mental health conditions. This study highlights the importance of monitoring HRQoL in people living with HIV due to the chronic nature of the disease. In this highly-treatment experienced group, disparities were found, particularly highlighting mental health as an area which needs more attention to improve the well-being of people living with HIV.

Effectiveness of COVID-19 vaccines in preventing SARS-CoV-2 infection and hospitalisation, Navarre, Spain, January to April 2021.

COVID-19 vaccine effectiveness was evaluated in close contacts of cases diagnosed during January-April 2021. Among 20,961 contacts, 7,240 SARS-CoV-2 infections were confirmed, with 5,467 being symptomatic and 559 leading to hospitalisations. Non-brand-specific one and two dose vaccine effectiveness were respectively, 35% (95% confidence interval (CI): 25 to 44) and 66% (95% CI: 57 to 74) against infections, 42% (95% CI: 31 to 52) and 82% (95% CI: 74 to 88) against symptomatic infection, and 72% (95% CI: 47 to 85) and 95% (95% CI: 62 to 99) against COVID-19 hospitalisation. The second dose significantly increased effectiveness. Findings support continuing complete vaccination.

Product-specific COVID-19 vaccine effectiveness against secondary infection in close contacts, Navarre, Spain, April to August 2021.

COVID-19 vaccine effectiveness by product (two doses Comirnaty, Spikevax or Vaxzevria and one of Janssen), against infection ranged from 50% (95% CI: 42 to 57) for Janssen to 86% (70 to 93) for Vaxzevria-Comirnaty combination; among ≥ 60 year-olds, from 17% (-26 to 45) for Janssen to 68% (48 to 80) for Spikevax; and against hospitalisation from 74% (43 to 88) for Janssen to > 90% for other products. Two doses of vaccine were highly effective against hospitalisation, but suboptimal for infection control.

Vaccine effectiveness against symptomatic SARS-CoV-2 infection in adults aged 65 years and older in primary care: I-MOVE-COVID-19 project, Europe, December 2020 to May 2021.

We measured COVID-19 vaccine effectiveness (VE) against symptomatic SARS-CoV-2 infection at primary care/outpatient level among adults ≥ 65 years old using a multicentre test-negative design in eight European countries. We included 592 SARS-CoV-2 cases and 4,372 test-negative controls in the main analysis. The VE was 62% (95% CI: 45-74) for one dose only and 89% (95% CI: 79-94) for complete vaccination. COVID-19 vaccines provide good protection against COVID-19 presentation at primary care/outpatient level, particularly among fully vaccinated individuals.

Prevalence and detection of undiagnosed active hepatitis C virus infections in Navarre, Spain, 2017-2019.

BACKGROUND: undiagnosed active hepatitis C virus (HCV) infection remains an obstacle towards its eradication. This study aimed to estimate the prevalence of HCV infection and to describe the diagnostic advances in Navarre, Spain. METHODS: HCV-infection diagnostic performance was analyzed in Navarre's primary and specialized health care between 2017 and 2019. The prevalence of undiagnosed infections was estimated for patients with programmed surgeries unrelated to HCV infection, who underwent a routine HCV antibody (anti-HCV) determination. HCV-RNA (viral load) was quantified in anti-HCV positive cases. The prevalence was standardized according to the sex and age distribution in the general population. RESULTS: from the 63,405 subjects examined for anti-HCV, 84 (five per 100,000 person-years) were diagnosed with an active infection. In Primary Health Care, 20,363 patients were analyzed and 47 active infections were detected, i.e. one case for every 433 people tested, implying 56 % of all identified active infections. On the other hand, 9,399 surgical patients were analyzed and 120 anti-HCV positive cases were detected (adjusted prevalence: 1.47 %; 95 % CI: 1.24-1.52). A positive viral load had been determined at any time in 66 cases (0.61 %), of which five were undiagnosed active infections (adjusted prevalence: 0.04 %; 95 % CI: 0.01-0.11). Preoperative screening allowed the detection of one undiagnosed infection per 795 people analyzed aged between 45 and 64 years. CONCLUSIONS: Primary Health Care efficiently contributes to the detection of undiagnosed HCV active infections. This may be speeded up by performing population screening, targeting subjects between 45 and 64 years of age.

Recapture of patients with an incomplete diagnosis of hepatitis C virus infection.

BACKGROUND: hepatitis C virus (HCV) antibody tests have been performed since the 90s, although HCV-RNA (viral load) determination was not always performed. Some of these patients may be actively infected and not be aware of it. Here, we describe a procedure to capture these subjects and complete their diagnosis. METHODS: the historical laboratory results of Navarra were reviewed and individuals who were positive for antibodies against HCV (anti-HCV) and had not undergone HCV-RNA testing were identified. In September 2018, each general practitioner (GP) was informed about their patients and given precise instructions for completing the diagnosis. The procedure was assessed until December 2019. RESULTS: two hundred and eighty-nine anti-HCV positive patients were detected for whom active infection had not been discarded. Two were HIV-positive and six had already died. GPs were asked to assess the remaining 281 subjects. By the end of 2019, a new blood test had been performed in 187 (67 %) patients, 5 % decided not to do it, 4 % were living outside of Navarra, 3 % could not be contacted and the GP considered that it was not justified in 2 % of cases. Thus, 19 % remained to be contacted. From the 187 assessed patients, active infection was confirmed in 52 (28 %) individuals, 40 % were false positives and HCV-RNA was undetectable in 31 %. Regarding the 52 actively infected subjects, 34 had already initiated antiviral therapy and three were hospitalized due to decompensated cirrhosis, from which one patient died. CONCLUSIONS: the strategy to recapture individuals with an incomplete HCV infection diagnosis was effective to detect active infections and subsequent initiation of antiviral therapy.

[COVID-19 infections, hospitalizations, and mortality in Navarre (Spain) between February 2020 and September 2022].

BACKGROUND: Between February 2020 and September 2022, SARS-CoV-2 has circulated uninterruptedly throughout Spain. This study analyses COVID-19 infections, hospitalizations, and deaths in Navarre. METHODS: Enhanced epidemiological surveillance and results of seroepidemiological surveys were used to analyze COVID-19 infections, hospitalizations, and deaths, based on the vaccination coverage and other preventive measures applied from February 2020 to September 2022. RESULTS: A total of 295,424 COVID-19 cases were confirmed (45% of the population in Navarre); 8,594 required hospital admission (1.3%), 832 were admitted to intensive care units (1.3‰) and 1,725 died (2.6‰). Over the first wave of the pandemic, there were 1,934 hospitalizations and 529 deaths from confirmed COVID-19 cases over a few weeks; these figures dropped rapidly following lockdown. Until October 2021, SARS-CoV-2 circulation was modulated by non-pharmacological preventive measures. The subsequent relaxation of these measures led to a wide circulation of the omicron variant, increasing the number of cases by three-fold. The high vaccination coverage against COVID-19 introduced decisive changes in the epidemiology of the disease, reducing to less than 2%, 0.1%, and 0.5% the cases requiring hospitalization, intensive care unit admission, or that died, respectively. CONCLUSIONS: Initial lockdown and non-pharmacological preventive measures helped control SARS-CoV-2 transmission until vaccination was extended. Vaccination achieved a decisive reduction of the COVID-19 severity and lethality.

Effectiveness of hepatitis C antiviral treatment and feasibility of hepatitis C elimination goal.

OBJECTIVES: Second-generation direct-acting antivirals (DAAs) have shown high efficacy in the treatment of chronic hepatitis C virus (HCV) infections in clinical trials. This study aimed to estimate the effectiveness in real-life conditions and their capacity to eliminate HCV infection in the general population. METHODS: In this observational cohort study, patients with active HCV infection who commenced DAA treatment between 2015 and 2020 in Navarre, Spain, were studied. Sustained virological response (SVR), defined as an undetectable viral load 12 weeks after the end of treatment, was evaluated until the end of 2021. RESULTS: Of a total 1366 HCV-infected patients that commenced treatment, 19.3% (n = 263) were HIV-coinfected. After the first DAA treatment, SVR was achieved in 96.6% (n = 1320/1366) of patients and in 97.7% (95% confidence interval [CI] 96.6%-98.3%) of those who completed treatment (per-protocol analysis; n = 1320/1351). SVR was achieved in 97.9% (n = 1066/1089) and 96.9% (n = 254/262) of mono-infected and HIV-coinfected patients, respectively. Thirty-one patients had virological failure due to non-response (n = 19), poor compliance (n = 9), and with adverse events (n = 3). Of 27 patients that received a second treatment, 24 attained SVR (one after a third treatment), two died, and one that did not achieve SVR declined a third treatment. Three patients were re-infected, re-treated, and achieved SVR. At the end of the study, 1344 patients (98.4%, 95% CI 97.6%-98.9%) had achieved SVR, and only 1.8% needed more than one course of treatment. All patients who completed the treatment and were followed-up achieved SVR. CONCLUSION: With DAAs, SVR was achieved in all patients with active HCV infection who completed follow-up, and a second course of treatment was only necessary in a small proportion of patients. Adherence to treatment is essential for HCV infection elimination.

Effect of COVID-19 vaccination on the SARS-CoV-2 transmission among social and household close contacts: A cohort study.

BACKGROUND: COVID-19 vaccination was expected to reduce SARS-CoV-2 transmission, but the relevance of this effect remains unclear. We aimed to estimate the effectiveness of COVID-19 vaccination of the index cases and their close contacts in reducing the probability of SARS-CoV-2 transmission. METHODS: Transmission of SARS-CoV-2 infection was evaluated in two cohorts of adult close contacts of COVID-19 confirmed cases (social and household settings) by COVID-19 vaccination status of the index case and the close contact, from April to November 2021 in Navarre, Spain. The effects of vaccination of the index case and the close contact were estimated as (1-adjusted relative risk) × 100%. RESULTS: Among 19,631 social contacts, 3257 (17%) were confirmed with SARS-CoV-2. COVID-19 vaccination of the index case reduced infectiousness by 44% (95% CI, 27-57%), vaccination of the close contact reduced susceptibility by 69% (95% CI, 65-73%), and vaccination of both reduced transmissibility by 74% (95% CI, 70-78%) in social settings, suggesting some synergy of effects. Among 20,708 household contacts, 6269 (30%) were infected, and vaccine effectiveness estimates were 13% (95% CI, -5% to 28%), 61% (95% CI, 58-64%), and 52% (95% CI, 47-56%), respectively. These estimates were lower in older people and had not relevant differences between the Alpha (April-June) and Delta (July-November) variant periods. CONCLUSIONS: COVID-19 vaccination reduces infectiousness and susceptibility; however, these effects are insufficient for complete control of SARS-CoV-2 transmission, especially in older people and household setting. Relaxation of preventive behaviors after vaccination may counteract part of the vaccine effect on transmission.

Assessment of Knowledge and Attitudes Over Time in Postacute COVID-19 Environments: Protocol for an Epidemiological Study.

BACKGROUND: Globally, COVID-19 is in transition from the acute pandemic phase into a postacute phase, and special attention should be paid at this time to COVID-19 control strategies. Understanding public knowledge and attitudes plays a pivotal role in controlling COVID-19's spread and provides information about the public's adherence to preventive and control measures. OBJECTIVE: This study protocol describes the planning and management of a survey to investigate the persistent or changing trends in knowledge and attitudes regarding COVID-19, vaccination, and nonpharmaceutical preventive measures among COVID-19 cases' household contacts aged 18 years and older, after the acute phase of the pandemic in Catalonia and Navarre in Spain. The secondary objectives include investigating the rate of secondary transmission in households, taking into account the demographic characteristics, clinical manifestations, and preventive measures toward COVID-19. METHODS: A telephone questionnaire was designed to assess the changing trends in knowledge, preventive measures, and attitudes toward COVID-19 in 3 rounds (after identification as a household contact, 3 months later, and 6 months later). The questionnaire was developed following an extensive literature review and through discussions with a panel of experts who designed and assessed the validity of the questionnaire in terms of relevance, consistency, completeness, and clarity. The questionnaire consists of the following 7 sections: social and demographic characteristics (ie, gender, age, educational level, and workplace), comorbidities and risk factors (according to the recommendations from the COVID-19 vaccination strategy), epidemiological data (ie, exposure time, relationship with index cases, and frequency of use of nonpharmaceutical preventive measures), COVID-19 vaccination status (ie, the number and date of doses received), knowledge and attitudes toward COVID-19 (assessed using a 5-point Likert scale-totally agree, agree, neither agree nor disagree, disagree, and totally disagree), and sources of information (including traditional mass media, social media, and official sources). RESULTS: A pilot study was performed in May 2022 to evaluate the questionnaire with 22 household contacts. Preliminary findings indicated that the questionnaire was feasible and acceptable in the general population. The average response time was 15 minutes, with greater variations in responses by older participants. After the pilot study, recruitment of participants began and is expected to be completed at the end of the year 2023, after which the final results will be available in 2024. CONCLUSIONS: Despite the low transmission levels of SARS-CoV-2 and the relaxation of containment measures, the implementation of the survey during the postacute phase will provide valuable insight to assist public health decision-making and control the transmission of SARS-CoV-2 and other respiratory viruses, thereby attenuating the negative effects of COVID-19 at individual and population level. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/52114.

Transmission of SARS-CoV-2 infection and risk factors in a cohort of close contacts.

PURPOSE: Many factors might affect SARS-CoV-2 transmission, but their relevance is not well established. The objectives were to assess the secondary attack rate (SAR) and the risk factors for SARS-CoV-2 transmission from confirmed index cases to their close contacts in household and non-household settings. METHODS: This cohort study included the close contacts of SARS-CoV-2 infected cases confirmed between May and December 2020 in Navarre, Spain. Epidemiological and clinical variables of the index case and close contacts were collected. The SAR was calculated, and the independent effect of each variable on the transmission risk was evaluated by logistic regression. RESULTS: A total of 59,900 close contacts of 20,048 index cases were studied, and 53.6% were household contacts. SAR was 34.9% overall, 46.8% in household contacts and 21.1% in non-household contacts. The risk of transmission was higher in household setting (adjusted odds ratio (aOR) 2.96, 95% CI 2.84-3.07), from symptomatic index cases (aOR 1.50, 95% CI 1.43-1.58), immigrants (aOR 1.44, 95% CI 1.36-1.52), and increased with age. A higher susceptibility of close contacts was associated with 5-14 years of age, immigrants (aOR 1.54), very low or low-income level (aOR 1.27, and aOR, 1.17, respectively), healthcare work (aOR 1.21), and diagnosis of diabetes (aOR 1.14, 95%CI 1.03-1.25), chronic kidney disease (aOR 1.18, 95%CI 1.04-1.35), hypertension (aOR 1.11, 95% CI 1.03-1.19), and severe obesity (aOR 1.18, 95% CI 1.00-1.38). Transmission increased progressively from May to September 2020 as the B.1.177 variant became dominant. CONCLUSION: The risk of SARS-CoV-2 infection was considerable among close contacts of infected persons. The higher risk associated with household contacts, immigrants, older index cases, close contacts with lower income level and comorbidities should be considered to address preventive interventions.

Differences in Transmission between SARS-CoV-2 Alpha (B.1.1.7) and Delta (B.1.617.2) Variants.

The present study aimed to compare the susceptibility and infectivity between the Alpha and Delta variants of SARS-CoV-2 and to investigate characteristics of the index case and the contact that may affect transmission. The risk of SARS-CoV-2 infection was compared between close contacts of COVID-19 cases with Alpha and Delta variants during June 2021 to August 2021. In index cases, Spike gene target failure (TaqPath) was used as a proxy of Alpha variant and the L452R mutation (TaqMan) for Delta variant. Cox regression models were used to estimate adjusted relative risks (RR). We compared close contacts of index cases with Alpha (n = 2139) and Delta variants (n = 5439). Delta variant was more transmissible overall (relative risk [RR] 1.32, 95% CI = 1.13 to 1.53), and in non-household contacts (RR 1.71, 95% CI = 1.35 to 2.16), but not in household contacts (RR 1.10, 95% CI = 0.91 to 1.34; Pinteraction < 0.001). Delta variant excess transmission was observed when the index cases were 12 to 39 years old (RR 1.51, 95% CI = 1.27 to 1.79) and the close contacts were 18 to 39 years old (RR 1.62, 95% CI = 1.29 to 2.03), but not among those younger or older than such ages. Differences in transmissibility between variants disappeared with vaccination of the index case (RR 0.68, 95% CI = 0.46 to 1.02), but not with vaccination of the close contact. This report shows that the Delta variant is more transmissible than Alpha variant mainly among young adults. Vaccination of the index cases reduced the excess transmission, which reinforces the recommendation of vaccination to reduce transmission of the Delta variant. IMPORTANCE The higher transmissibility of the Delta variant of SARS-CoV-2 in comparison with the Alpha variant has been reported. We compared the transmission of the Alpha and Delta variants by characteristics and COVID-19 vaccination status of index cases and their close contacts. Interestingly, the Delta variant showed increased transmissibility when the index case was an adolescent or young adult and when the close contact was a young adult; however, in index cases and close contacts of other age groups, transmission did not differ between variants. This may explain the increased proportion of young people who have been infected in the surges due to the Delta variant. The Delta variant was more transmissible than the Alpha variant when the index cases were unvaccinated against COVID-19, and their vaccination equaled the transmissibility of both variants, which suggests a higher impact of vaccination in controlling transmission of the Delta variant.