ABSTRACT
We evaluated the protection afforded by SARS-CoV-2 natural infection against reinfection among vaccinated during a calendar period from June to August 2022 when Omicron BA.5 was the dominating subvariant in Scania county, Sweden. We formed a study cohort (n = 71 592) mainly consisting of health care workers by restricting to people 18-64 years old who received their first vaccine dose relatively early (24 April 2021 or sooner). We used continuous density case-control 1:10 sampling matched for sex and age within the study cohort, and thereby obtained 1 114 cases during Omicron BA.5 dominance and 11 140 controls who were analysed with conditional logistic regression. Limited protection against reinfection was suggested from prior infection of virus variants before Omicron (11%, 95% confidence interval [CI] -10 to 28%]. By contrast, prior Omicron infection offered clear protection (65%, 95% CI 56-73%). For the Omicron BA.2 subvariant, stronger protection was suggested during early (85%, 95% CI 75-91%) than later BA.5 dominance (66%, 95% CI 48-78%). Lower protection was observed from the previous BA.1 subvariant (30%; 95% CI -4 to 53%). These findings suggest that natural infection from the Omicron subvariants contributes to short-term population protection against reinfection with the subvariant BA.5 among vaccinated, but wanes considerably 5-6 months after infection.
ABSTRACT
We compared vaccine effectiveness (VE) against severe COVID-19 during calendar periods from December 2021 to March 2022 when Omicron BA.1 and BA.2, respectively, were the dominating virus variants in Scania county, Sweden. We used continuous density case-control sampling matched for sex and age, and with further adjustment for differences in comorbidities and prior infection. VE remained relatively stable after the transition from BA.1 to BA.2 among people with at least three doses but decreased markedly among those with only two doses. Protection from prior infection was also lower after the transition to BA.2. These findings suggest that booster vaccination is needed to maintain sufficient protection against severe COVID-19.
ABSTRACT
The risk of severe COVID-19 disease requiring hospitalization with extensive oxygen supply was compared among infected cases during two calendar periods when Delta and Omicron, respectively, were the dominating virus variants in Scania county, Sweden. Adjustments were made for differences among cases in comorbidities, prior infection, vaccination status, age and sex. Markedly lower risks were observed from Omicron among the vaccinated in the present study. The risk of severe disease was also lower for unvaccinated during Omicron than during Delta, but remained high among older people and middle-aged males with comorbidities. Efforts to increase vaccination uptake across countries, populations and subgroups should thus remain a public health priority.
ABSTRACT
(ii)BackgroundTo prevent nosocomial transmission of SARS-CoV-2, infection control measures are implemented for patients with symptoms compatible with COVID-19 until reliable test results are available. This delay targeted admission to the most appropriate ward based on the medical condition. SARS-CoV-2 rapid antigen detection (RAD) tests and point of care (POC) rapid RT-PCR were introduced at emergency departments (EDs) in late 2020, but the consequence on targeted admission is unknown. ObjectivesTo assess the effect of RAD tests and POC rapid RT-PCR (VitaPCR, Credo Diagnostics, Singapore) on targeted admission. MethodsPatients presenting at the ED of a referral hospital (N = 2,940) between 13-Nov-2020 and 12-Jan-2021 were included. The study period was delimited by introduction of RAD tests and VitaPCR. Participant data was collected retrospectively, and outcome variables were length-of-stay (LoS), intrahospital transfers and targeted admission to COVID-19 ward. ResultsRAD tests reduced ED LoS for participants with positive tests or that were not tested. Negative VitaPCR results reduced mean hospital LoS by 1.5 (95%CI: 0.3-2.7) days and admissions to COVID-19 wards from 34.5 (95%CI: 28.9-40.5) to 14.7 (95%CI: 11.1-19.1) per 100 admissions. Introduction of VitaPCR reduced transfers between hospital wards in the first 5 days from 50.0 (95%CI: 45.0-55.0) to 34.0 (95%CI: 30.3-37.9) per 100 admissions. ConclusionRAD tests enabled rapid detection of SARS-CoV-2 infection which had pronounced effects on LoS at the ED. VitaPCR added the possibility of exclusion of the infection which increased targeted admissions, reduced intrahospital transfers and lead to shorter stay at the hospital.
ABSTRACT
The extensive register infrastructure available for COVID-19 surveillance in Scania county, Sweden, makes it possible to classify cases with respect to hospitalization and disease severity, stratify on time since last dose and demographic factors, account for prior infection, and extract data for population controls automatically. Estimated vaccine effectiveness 0-3 months after the last dose remained stable during the study period but waned markedly 6 months after the last dose in older persons.
ABSTRACT
The aim of this cohort study was to investigate sociodemographic determinants of COVID-19 vaccine uptake in the 70+ age group in Sk[a]ne county, Sweden (n = 216 243 at baseline). Uptake of the first dose was high (91.9%) overall, but markedly lower (75.3%) among persons born outside the Nordic countries. Vaccine uptake was generally satisfactory among native Swedes also in areas with lower socioeconomic status, but dropped substantially among non-Nordic born in those areas. The identified clusters of unvaccinated older people, mainly representing ethnic minorities in disadvantaged areas, warrants intensified efforts regarding tailored communication, easier vaccine access and local engagement. Key pointsO_LICOVID-19 vaccine uptake in the 70+ age group in Sk[a]ne county, Sweden, was high (91.9%) overall, but markedly lower (75.3%) within the group born outside the Nordic countries C_LIO_LIInverse associations between indicators of neighbourhood deprivation and vaccine uptake were observed, which lowered the uptake among persons born outside the Nordic countries further C_LIO_LIThe identified clusters of unvaccinated older people, mainly representing ethnic minorities in disadvantaged areas, warrants intensified efforts regarding tailored communication, easier vaccine access and local engagement C_LI
ABSTRACT
ObjectivesTo study the impact of non-mandatory, age-specific social distancing recommendations for older adults (70+ years) in Sweden on isolation behaviors and disease outcomes during the first wave of the COVID-19 pandemic. MethodsOur study relies on self-reported isolation data from COVID Symptom Study Sweden (n = 96,053) and national register data on COVID-19 hospitalizations, deaths, and confirmed cases. We use a regression discontinuity design to account for confounding factors, exploiting the fact that exposure to the recommendation was a discontinuous function of age. ResultsBy comparing individuals just above to those just below the age limit for the policy, our analyses revealed a sharp drop in the weekly number of visits to crowded places at the 70-year-threshold (-13%). Severe COVID-19 cases (hospitalizations or deaths) also dropped abruptly by 16% at the 70-year-threshold. Our data suggest that the age-specific recommendations prevented approximately 1,800 to 2,700 severe COVID-19 cases, depending on model specification. ConclusionThe non-mandatory, age-specific recommendations helped control the COVID-19 pandemic in Sweden.
ABSTRACT
BackgroundVaccine effectiveness against COVID-19 needs to be assessed in diverse real-world population settings. MethodsA cohort study of 805 741 residents in Sk[a]ne county, Southern Sweden, aged 18-64 years, of whom 26 587 received at least one dose of the BNT162b2 vaccine. Incidence rates of COVID-19 were estimated in sex- and age-adjusted analysis and stratified in two-week periods with substantial community spread of the disease. ResultsThe estimated vaccine effectiveness in preventing infection [≥]7 days after second dose was 86% (95% CI 72-94%) but only 42% (95% CI 14-63%) [≥]14 days after a single dose. No difference in vaccine effectiveness was observed between females and males. Having a prior positive test was associated with 91% (95% CI 85 to 94%) effectiveness against new infection among the unvaccinated. ConclusionA satisfactory effectiveness of BNT162b2 after the second dose was suggested, but with possibly substantially lower effect before the second dose.
