key: cord-0979588-mx1d9qqg authors: Starrfelt, J.; Danielsen, A. S.; Kacelnik, O.; Borseth, A. W.; Seppala, E.; Meijerink, H. title: High vaccine effectiveness against COVID-19 infection and severe disease among residents and staff of long-term care facilities in Norway, November - June 2021 date: 2021-08-09 journal: nan DOI: 10.1101/2021.08.08.21261357 sha: 86fe9d187bdcf6585e423c5ab166b11f8d3864fb doc_id: 979588 cord_uid: mx1d9qqg COVID-19 has caused high morbidity and mortality in long-term care facilities (LTCFs) worldwide. We estimated vaccine effectiveness (VE) among residents and health care workers (HCWs) in LTCFs using Cox regressions. The VE against SARS-CoV-2 infection was 81.5 (95%CI: 75.3-86.1 82.7%) and 81.4% (95%CI: 74.5-86.4%) 7 days or more after 2nd vaccine dose among residents and staff respectively. The VE against COVID-19 associated death was 93.1% among residents, no hospitalisations occurred among HCW 7 days or more after 2nd dose. High age is the main factor associated with severe outcomes for COVID-19. SARS-CoV-2 outbreaks in long-term care facilities (LTCFs) have caused a large burden of disease. To open society without excess mortality while preserving healthcare capacity, many countries, including Norway, prioritised vaccinating residents and staff of LTCFs [1] [2] [3] . This policy is dependent on a sufficient vaccine effectiveness (VE) in this population. Norway has the unique opportunity to follow both staff and residents for a complete picture of VE in this setting. The need for understanding VE is also vital for determining what kind of infection prevention and control measures are required. The balance between safety and quality of life is a fine line in LTCFs. Only a few studies have assessed the effect of COVID-19 vaccination among residents of LTCFs [1, [3] [4] [5] [6] ; showing that COVID-19 vaccines reduce both infections and severity of disease. Furthermore, a high VE in staff and residents is crucial for protecting individuals unable or unwilling to take the vaccine. In this cohort study, we estimate the effectiveness of COVID-19 vaccines in preventing PCR-confirmed SARS-CoV-2 infections in residents and staff of LTCFs, COVID-19 associated hospitalisation in staff and deaths in residents as a proxy for severe disease, to provide evidence for guidance and implementation of COVID-19 vaccination programmes. Determining vaccine effectiveness in long-term care facilities We obtained data from BeredtC19, a preparedness registry containing individual-level data from various Norwegian registries (Supplementary table S1) [7] . We included data six weeks prior to vaccination start in Norway (27 th of December 2020), up to a PCR positive SARS-CoV-2 test, hospitalisation with COVID-19 as primary diagnosis or COVID-19 associated death, death from any cause, or end of follow-up (15th June 2021). We included all HCWs employed at LTCFs in the third week of January 2021 and residents registered with a long-term stay at a LTCF in 2020. We excluded those with prior SARS-CoV-2 infection, and individuals where the interval between first and second dose did not adhere to national recommendations [8, 9] . Underlying conditions were categorized as "high risk" or "medium risk" as stipulated by the national vaccination programme [10] . Vaccination status was defined as: -Unvaccinated: unvaccinated, <14 days after 1 st vaccine dose -Partly vaccinated_≥14 days after 1 st vaccine dose, <6 days after 2 nd vaccine dose -Fully vaccinated: ≥7 days after 2 nd vaccine dose. We included 31489 residents, of whom 85.4% (26905) received at least 1 dose during the follow-up period compared to 71.1% (63000) of the 88 549 HCWs. The median age was 87 years (IQR: 81-92 years) for residents and 39 (IQR: 27-53 years) for HCWs. Characteristics of the study population are shown in table 1. The incidence rates of COVID-19 outcomes were associated with vaccination status in both residents and HCWs (figure 1). . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted August 9, 2021. ; . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted August 9, 2021. ; Residents of long-term care facilities The VE against PCR positive SARS-CoV-2 was 81.5% among fully vaccinated residents. Sex, age, and underlying conditions had limited effect on the estimates, probably due to the relatively uniform population characteristics (Table 2) . Despite significantly lower incidence rates (figure 1), we could not show protection among partly vaccinated residents using cox proportional hazard models. This can be explained by the quick vaccination roll-out (90% had received their first dose by 20 January), and the limited time contributed as partly vaccinated since residents received their second dose three weeks after first. This effect may also be compounded by a high all-cause mortality. In Norway, residents of LTCFs often receive health care at the facility and are not admitted to hospitals unless it is in the best interests of the resident. This population has the highest COVID-19 mortality, we therefore estimated the VE against COVID-19 associated death. 6 710 residents died during the study period, of whom 137 died with COVID-19. The VE against COVID-19 associated death was 93.1% among fully vaccinated individuals (table 2). (Table 3 ). In Norway, COVID-19 associated mortality in the general population is low, therefore we used hospital admissions with COVID-19 as primary diagnosis as a measure of disease severity in HCWs. 56 individuals were hospitalised with COVID-19 as their primary diagnosis, of which two were among partly vaccinated and none fully vaccinated. The adjusted VE against COVID-19 hospitalisation was 81.7% for partly vaccinated HCWs in LTCFs (table 3) . . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted August 9, 2021. ; Table 3 . Estimated crude and adjusted COVID-19 vaccine effectiveness (VE) against laboratory confirmed SARS-CoV-2 and hospitalisation with COVID-19 as main cause among health care workers of long-term care facilities (LTCF). We found a high VE against both SARS-CoV-2 infection and severe disease in residents and HCWs in LTCFs in Norway. Our estimates coincide with other studies looking at similar settings with high disease burden such as LTCFs [1] [2] [3] [4] [5] [6] [11] [12] [13] . Importantly, we showed that one vaccine dose protected well against hospital admission among HCWs. In Norway, residents of LTCFs were identified as very vulnerable and prioritized for vaccination. Vaccination roll-out in this group was quick and efficient [8] . Vaccination might be withheld for medical reasons, for example frailty or a history of severe allergic reactions to vaccines [14] . Persons with contraindications to vaccination are also those with the highest risk of severe outcomes after COVID-19, which could bias the VE estimate downwards. However, this bias seems to be limited, as can be seen from the lack of effect of age, sex, and underlying conditions on the VE. We found that the VE against both SARS-CoV-2 infection and hospitalisation in HCWs was high also after one dose. The number of HCWs admitted to hospital in relation to COVID-19 is low but even lower post vaccination. Furthermore, the total protection for unvaccinated residents is significantly increased through staff vaccination. The effect of one dose also underlines the importance of ensuring temporary staff have received one dose prior to work in LTCFs. Several methodological aspects should be considered when interpreting our data. Testing around cases in LTCFs has been extensive and continues for 10 days after the last case, reducing the risk of bias. As the time between the two vaccine doses was three weeks for residents, the follow-up time for partly vaccinated residents was limited and could explain why we didn't demonstrate a significant effect of first vaccination, even on a background of reduced incidence per 100,000. A similar scenario was reported in Denmark [4] . The outcomes of this study are essential for the guidance of COVID-19 measures in LTCFs. Our results showcase the importance of quickly achieving full protection among the frail and elderly, and the effectiveness of one dose in healthcare workers. The pandemic has restricted the life of residents in LTCF. Through better knowledge, we can adjust COVID-19 guidelines for residents in LTCFs to fewer, targeted measures which might contribute to better quality of life. This knowledge is transferable to similar situations, like influenza, where vaccination of both residents and HCWs is of particular importance. 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