Cohort Profile: The Danish National Cohort Study of Effectiveness and Safety of SARS-CoV-2 vaccines (ENFORCE) (original) (raw)
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PLOS ONE, 2021
Background In Finland, both mRNA and adenovirus vector (AdV) Covid-19 vaccines have been used after the vaccination campaign started on December 27, 2020. Vaccination of the elderly and chronically ill was prioritized and the interval between doses set to 12 weeks. The objective of this interim analysis was to evaluate first and second dose vaccine effectiveness (VE) in a real-world setting. Methods During the first five months of the campaign, a register-based cohort study was conducted in the Finnish elderly aged 70+ years and those aged 16-69 years with medical conditions predisposing to severe Covid-19 (chronically ill). Using Cox regression, VE against SARS-CoV-2 infection and Covid-19 hospitalisation was estimated comparing the hazard in the vaccinated with that in the unvaccinated. Results The cohorts included 901092 elderly (89% vaccinated) and 774526 chronically ill (69% vaccinated) individuals. Three weeks after the first dose, mRNA VE against infection was 45% (95% confidence interval, 36-53%) and 40% (26-51%) in elderly and chronically ill; mRNA VE against hospitalisation was 63% (49-74%) and 82% (56-93%). In chronically ill, AdV VE was 42% (32-50) and 62% (42-75%) against infection and hospitalisation, respectively. One week after the second dose, mRNA VE against infection was 75% (65-82%) and 77% (65-85%) in elderly and chronically ill; mRNA VE against hospitalisation was 93% (70-98%) and 90% (29-99%).
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Scientific Reports, 2023
SARS-CoV-2 vaccination is currently the mainstay in combating the COVID-19 pandemic. However, there are still people among vaccinated individuals suffering from severe forms of the disease. We conducted a retrospective cohort study based on data from nationwide e-health databases. The study included 184,132 individuals who were SARS-CoV-2 infection-naive and had received at least a primary series of COVID-19 vaccination. The incidence of BTI (breakthrough infection) was 8.03 (95% CI [confidence interval] 7.95⎼8.13/10,000 person-days), and for severe COVID-19 it was 0.093 (95% CI 0.084⎼ 0.104/10,000 person-days). The protective effect of vaccination against severe COVID-19 remained constant for up to six months, and the booster dose offered an additional pronounced benefit (hospitalization aHR 0.32, 95% CI 0.19⎼0.54). The risk of severe COVID-19 was higher among those ≥ 50 years of age (aHR [adjusted hazard ratio] 2.06, 95% CI 1.25⎼3.42) and increased constantly with every decade of life. Male sex (aHR 1.32, 95% CI 1.16⎼1.45), CCI (The Charlson Comorbidity Index) score ≥ 1 (aHR 2.09, 95% CI 1.54⎼2.83), and a range of comorbidities were associated with an increased risk of COVID-19 hospitalization. There are identifiable subgroups of COVID-19-vaccinated individuals at high risk of hospitalization due to SARS-CoV-2 infection. This information is crucial to driving vaccination programs and planning treatment strategies. Large-scale vaccination programs against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) deployed by governments and health authorities in more than 200 countries 1 have halted coronavirus disease 2019 (COVID-19)-associated mortality and caused people worldwide to anticipate the oncoming end of the pandemic. Clinical trials, as well as studies tracking real-world data, demonstrated the pronounced effectiveness of COVID-19 vaccines against SARS-CoV-2 infection and severe COVID-19 2. People at increased risk of severe COVID-19 were among the first to be involved in vaccination programs in many countries 3,4. This probably helped prevent the collapse of health systems in these countries and maintain economic activity 5. By the end of the second year of the pandemic, the increased number of people with vaccineinduced immunity together with the emergence of new, more contagious but less virulent strains of the virus yielded a drop in COVID-19-associated hospitalizations and deaths worldwide 6. These developments reduced caution regarding COVID-19 and led to alleviation of coronavirus-related containments. Therefore, the "flattening the curve" strategy with a main emphasis on limiting population mobility and contact tracing was replaced by less stringent measures and focused on the protection of vulnerable populations by encouraging vaccine uptake 7,8. Vaccines prevent severe COVID-19, although their ability to prevent infections even in highly vaccinated populations fades due to the ability of new strains to evade the immune response 9-12. Vaccinated individuals account for at least one-third of all people hospitalized due to COVID-19. Thus, the threat of COVID-19 is not