National study shows the link between COVID vaccination and reduced household transmission in Sweden
As members of society increasingly acquire COVID immunity through vaccination or previous infection, people without immunity to COVID-19 are at significantly lower risk of infection and hospitalization. It shows a nationwide study conducted by researchers at Umeå University.
“The results strongly suggest that vaccination is important not only for individual protection, but also to reduce transmission, especially in families, which is a highrisk environment for transfer ”, says Peter Nordström, professor of geriatric medicine at Umeå University.
There is a large amount of research that shows that vaccines greatly reduce the risk of COVID-19. However, less is known about the influence of vaccination on the transmission of the virus in high-risk environments, for example in families. This was what researchers at Umeå University wanted to investigate in a new study.
In the study, the researchers found that there was a dose-response relationship between the number of immune individuals in each family and the risk of infection and hospitalization of non-immune family members. Specifically, non-immune family members had a 45 to 97 percent lower risk of infection and hospitalization as the number of immune family members increased.
The study is a nationwide, registry-based study of more than 1.8 million individuals from more than 800,000 families. The researchers combined register data from the Swedish Public Health Agency, the National Board of Health and Welfare and from Statistics Sweden, which is authority which monitors statistical data. In the analysis, the researchers quantified the relationship between the number family members with COVID-19 immunity and risk of infection and hospitalization in non-immune individuals. The researchers reported differences in age, socio-economic status, grouping within families and several diagnoses that have previously been identified as risk factors for COVID-19 in the Swedish population.
“It seems that vaccination not only helps to reduce the individual’s risk of becoming infected, but also to reduce transmission, which in turn minimizes not only the risk of more people becoming critically ill, but also that new problematic variants emerge and begin to take over. Consequently, ensuring that many people are vaccinated has consequences at the local, national and global level, ”says Marcel Ballin, doctoral student in geriatric medicine at Umeå University and co-author of the study.
The study is published in JAMA Internal Medicine.
Relationship between the risk of COVID-19 infection in non-immune individuals and COVID-19 immunity in their family members, JAMA Internal Medicine (2021). DOI: 10.1001 / jamainternmed.2021.5814
Nationwide study shows the link between COVID vaccination and reduced household transmission in Sweden (2021, 11 October)
retrieved October 11, 2021
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