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ObjectivesThe emergence of SARS-CoV-2 variants raised questions over the extent to which vaccines designed in 2020 have remained effective. We aimed to assess whether vaccine status was associated with the severity of Omicron SARS-CoV-2 infection in hospitalised patients. MethodsWe conducted an international, multicentric, retrospective study in 14 centres (Bulgaria, Croatia, France, Turkey). We collected data on patients hospitalised [≥]24 hours between 01/12/2021 and 03/03/2022, with PCR-confirmed infection at a time of exclusive Omicron circulation, with hospitalisation related or not to the infection. Patients who had received prophylaxis by monoclonal antibodies were excluded. Patients were considered fully vaccinated if they had received at least 2 injections of either mRNA and/or ChAdOx1-S, or 1 injection of Ad26.CoV2-S vaccines. ResultsAmong the 1215 patients (median [IQR] age 73.0 [57.0; 84.0]; 51.3% males), 746 (61.4%) were fully vaccinated. In multivariate analysis, being vaccinated was associated with lower 28-day mortality (RR=0.50 [0.32-0.77]), ICU admission (R=0.40 [0.26-0.62], and oxygen requirement (RR=0.34 [0.25-0.46]), independently of age and comorbidities. When co-analysing these Omicron patients with 948 Delta patients from a study we recently conducted, Omicron infection was associated with lower 28-day mortality (RR=0.53 [0.37-0.76]), ICU admission (R=0.19 [0.12-0.28], and oxygen requirements (RR=0.50 [0.38-0.67]), independently of age, comorbidities and vaccination status. ConclusionsmRNA- and adenovirus-based vaccines have remained effective on severity of Omicron SARS-CoV-2 infection. Omicron is associated with a lower risk of severe forms, independently of vaccination and patient characteristics.
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BackgroundThe diffusion of the SARS-CoV-2 delta (B.1.617.2) variant and the waning of immune response after primary Covid-19 vaccination favoured the breakthrough SARS-CoV-2 infections in vaccinated subjects. To assess the impact of vaccination, we determined the severity of infection in hospitalised patients according to vaccine status. MethodsWe retrospectively analysed data from patients hospitalised in 10 centres with a SARS-CoV-2 infection (delta variant) from July to November 2021: i) all patients who had completed their primary vaccination at least 14 days before hospital admission; and ii) the same number of completely unvaccinated patients. We assessed the impact of vaccination and other risk factors through logistic regression. FindingsWe included 955 patients (474 vaccinated and 481 unvaccinated). Vaccinated patients were significantly older, more frequently males, and with more comorbidities. They were less often admitted for Covid-19 (59{middle dot}3% vs. 75{middle dot}1%, p<0{middle dot}001), showed fewer lung lesions, and required oxygen less frequently (57{middle dot}5% vs. 73{middle dot}0%, p<0{middle dot}001), at a lower flow (3{middle dot}0 vs. 6{middle dot}0 L/min, p<0{middle dot}001), and for a shorter duration (3 vs. 6 days, p<0{middle dot}001). They less frequently required intensive care unit admission (16{middle dot}2 % vs. 36{middle dot}0 %, p<0{middle dot}001). Mortality at day 28 was not different between the two groups (16{middle dot}7% vs. 12.2%, p=0{middle dot}075), but multivariate logistic regression showed that vaccination significantly decreased the risk of negative outcomes, including mortality, even when considering older patients, and those with comorbidities. ConclusionsAmong patients hospitalised with a delta variant SARS-CoV-2 infection, vaccination was associated with less severe forms, even in the presence of comorbidities.
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BackgroundSince the beginning of the COVID-19 pandemic, many countries, including Canada, have adopted unprecedented physical distancing measures such as closure of schools and non-essential businesses, and restrictions on gatherings and household visits. We described time trends in social contacts for the pre-pandemic and pandemic periods in Quebec, Canada. MethodsCONNECT is a population-based study of social contacts conducted shortly before (2018/2019) and during the COVID-19 pandemic (April 2020 - February 2021), using the same methodology for both periods. We recruited participants by random-digit-dialing and collected data by self-administered web-based questionnaires. Questionnaires documented socio-demographic characteristics and social contacts for two assigned days. A contact was defined as a two-way conversation at a distance [≤]2 meters or as a physical contact, irrespective of masking. We used weighted generalized linear models with a Poisson distribution and robust variance (taking possible overdispersion into account) to compare the mean number of social contacts over time by characteristics. ResultsA total of 1291 and 5516 Quebecers completed the study before and during the pandemic, respectively. Contacts significantly decreased from a mean of 8 contacts/day prior to the pandemic to 3 contacts/day during the spring 2020 lockdown. Contacts remained lower than the pre-COVID period thereafter (lowest=3 contacts/day during the Christmas 2020/2021 holidays, highest=5 in September 2020). Contacts at work, during leisure activities/other locations, and at home with visitors showed the greatest decreases since the beginning of the pandemic. All sociodemographic subgroups showed significant decreases of contacts since the beginning of the pandemic. The mixing matrices illustrated the impact of public health measures (e.g. school closure, gathering restrictions) with fewer contacts between children/teenagers and fewer contacts outside of the three main diagonals of contacts between same-age partners/siblings and between children and their parents. ConclusionPhysical distancing measures in Quebec significantly decreased social contacts, which most likely mitigated the spread of COVID-19.
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Remdesivir and dexamethasone are the only drugs providing reductions in the lengths of hospital stays for COVID-19 patients. We assessed the impacts of remdesivir on hospital-bed resources and budgets affected by the COVID-19 outbreak. A stochastic agent-based model was combined with epidemiological data available on the COVID-19 outbreak in France and data from two randomized control trials. Strategies involving treating with remdesivir only patients with low-flow oxygen and patients with low-flow and high-flow oxygen were examined. Treating all eligible low-flow oxygen patients during the entirety of the second wave would have decreased hospital-bed occupancy in conventional wards by 4% [2%; 7%] and intensive care unit (ICU)-bed occupancy by 9% [6%; 13%]. Extending remdesivir use to high-flow-oxygen patients would have amplified reductions in ICU-bed occupancy by up to 14% [18%; 11%]. A minimum remdesivir uptake of 20% was required to observe decreases in bed occupancy. Dexamethasone had effects of similar amplitude. Depending on the treatment strategy, using remdesivir would, in most cases, generate savings (up to 722{euro}) or at least be cost neutral (an extra cost of 34{euro}). Treating eligible patients could significantly limit the saturation of hospital capacities, particularly in ICUs. The generated savings would exceed the costs of medications.
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In the first trimester 2020, a significant number of countries implemented general lockdowns of their populations to contain the quickly expanding SARS-CoV-2 epidemic and avoid major saturation of health care capacity. Understanding how these unprecedented measures impacted population behaviour and contact patterns is key to predict more accurately the health, social and economic impacts of such extreme actions if they were to be applied to future outbreaks. We set up an online survey to measure how the lockdown affected social contact patterns in France, and collected information from 42,036 participants aged 18 years and over between April 10 and April 28, 2020. Among the participants who normally worked outside home prior to the lockdown (72% of the survey population), 68% reported that they had moved to working from home and 17% reported being unemployed during the lockdown. Only 2% of participants used public transport during lockdown, as opposed to 37% before it. Participants reported increased frequency of washing hands, switch in greeting behaviour, but generally limited use of masks outside home. 138,934 contacts were reported, with an average 3.3 contacts per individual per day (1.7 for individuals aged >65 years old compared to 3.6 for younger age-groups). This represented a 70% reduction compared with previous surveys, consistent with reductions in transmission rates measured during the lockdown. Contacts in workplaces, shops, and transports on the previous day were respectively reported in only 11%, 31% and 0.5% of the participants. For those who maintained a professional activity outside home, the frequency of contacts at work dropped by 79%. This study shows that the lockdown dramatically affected populations behavior, work, risk perception and contact patterns. Both frequency and heterogeneity of contacts were affected, impacting potential important features of virus dissemination. Such surveys are essential to evaluate more accurately the impact of past or future lockdowns and anticipate epidemic dynamics in these conditions.
