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Swedish epidemiological study shows early programmatic effects of immunizing people over 80, residents of long-term care facilities (LTCFs) and people receiving home care can successfully reduce infection rates and mortality caused by the severe acute respiratory syndrome coronavirus. 2 (SARS-CoV-2). The document is currently available on the medRxiv* preprint server while undergoing peer review.
Study: The early impact of SARS-CoV-2 vaccination in the region of Stockholm, Sweden. Image Credit: Hyserb / Shutterstock
introduction
The 2019 coronavirus disease (COVID-19) vaccination programs in Sweden prioritize those most at risk of serious illness from SARS-CoV-2 infection, with the ultimate goal of protecting more vulnerable and, in turn, the health system as a whole.
There are four main phases introduced in Sweden since the start of the program. In the first phase, all adults living in LTCHs, those receiving home care and their family contacts, and health personnel working with them were given priority to receive the vaccine.
Then, the program covered adults over 65, transplant recipients and those on dialysis in the second phase. The third phase covered adults with other risk factors, and then finally, adults without risk factors over the age of 18 were part of phase four.
In Stockholm, phase 1 vaccination began on December 27, 2020, while phase two began on March 8, 2021, inviting adults over 80 years old. On March 29, 2021, adults over 75 were also invited.
In this study, the researchers wanted to assess the exact early impact of the vaccination program that was introduced in Stockholm.
A population-based approach
This population-based retrospective study aimed to assess the incidence of SARS-CoV-2 and subsequent deaths within thirty days of a PCR-confirmed diagnosis in the cohorts targeted for vaccination, and then compare the results with a control group. not targeted for vaccination.
Three mutually exclusive groups were defined for this study: those in ELD or receiving home care, those aged 80 or older (80+), and a composite control of those aged 18 to 79. The data was extracted from the Swedish VAL database, which contains information from more than ten other healthcare-related databases in the Stockholm region.
The analyzes for this study were limited to a period between August 31, 2020 and May 2, 2021, to cover both the second and third waves of COVID-19 in Stockholm. Conversely, data from the first wave was not included due to the lack of widely available tests when the pandemic just started.
A significant drop in infections and deaths
The highest number of SARS-CoV-2 infections was recorded in the control group (182,695). On the other hand, there were more infections in the LTC / home care group (5232 pre-vaccination and 1537 post-vaccination) compared to the 80+ group (2276 pre-186 post-vaccination).
The study estimated that vaccination could prevent 2,873 infections in the LTC / home care group and 239 in the 80+ group, while the estimated number of deaths averted was 808 for the LTC / home care group and 46 for the 80+ group. During the study period, more deaths were recorded in the LTC / home care group within 30 days of a positive SARS-CoV-2 test.
In addition, the incidence rate ratio (IRR) for fatal outcomes within 30 days of a positive PCR test for SARS-CoV-2 increased from 179 before vaccination to 45 after vaccination for the LTCH / care group. home, as well as from 20 before vaccination to 9 after vaccination for the 80+ group, compared to the composite control.
Prevent the third wave
The authors suggest that vaccination of the LTCF / home care and 80+ groups was successful in preventing a third wave in these groups of the same size as the control group.
However, the study has certain limitations. He was unable to link vaccine data at the individual level to recent studies conducted in Israel, and vaccine coverage data was primarily based on LTCF and age.
In conclusion, the first programmatic effects of immunizing two of the most vulnerable groups in Sweden were successful in reducing rates of SARS-CoV-2 infection and deaths. While encouraging, further research on this topic will shed more light on the optimal approach.
*Important Notice
medRxiv publishes preliminary scientific reports which are not peer reviewed and, therefore, should not be considered conclusive, guide clinical practice / health-related behavior, or treated as established information.
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