A study of over 800,000 Swedish families shows a 45 to 97% reduction in the risk of infection. The effects of the family bubble resemble a herd mini-immunity against the coronavirus
More than one family member is vaccinated (or recovered from Covid), then immunized, the more the risk of coronavirus infection is reduced: 45% -61% lower if 1 person in the family has been vaccinated (or previously infected), 75-86% if 2 people are immunized, 91-94% if there are 3 and 97% if there are 4 immunized members.
Risk reduction up to 97%
The study that calculated these percentages was published on 11 October in the scientific journal JAMA
and was conducted in Sweden on 1,789,728 individuals from 814,806 families. Each family comprised 2 to 5 members, with an average age of 51.3 years. The basic characteristics of non-immune individuals were: lower median age (27.3 years), fewer medical diagnoses (such as myocardial infarction), lower median income, and a lower percentage of individuals born in Sweden. The results held up against newly registered infections within the family context between April 15 and May 26, 2021. In that period 88,797 people became infected, 5.7% of the total considered. As written, in families with 1 vaccinated member, non-immune had a 45% to 61% lower risk of contracting Covid, regardless of family size, in families with 2 vaccinated members, other family members had a lower risk from 75 % to 86, further reduced from 91% to 94% in families with 3 vaccinated (or previously cured) members and in families with 5 members, 4 of which immune, the remaining non-immune member had a 97% lower risk. The results were similar even when the infection was severe enough to cause a hospital stay: for example, in families with 3 members, of which 2 were immune, the remaining non-immune family member had an 80% lower risk.
Results with the Alfa variant
A notable detail emerged then, that the benefits were similar regardless of whether immunity was acquired from a previous one infection, a single dose of vaccine, or a full vaccination. These findings suggest that vaccines play a key role in reduce virus transmission within families, which likely has implications for herd immunity and pandemic control, the research authors write. The results and conclusions of this study, including single dose data, they apply only to the Alpha variant, which has determined more than 95% of all Covid cases followed in the research, warn scientists, recalling that the protection of a single dose against the Delta proved, in other studies, to be insufficient.
The family bubble
However, they reiterate that, beyond the specific percentages, the reasoning on community protection remains valid, even with the Delta variant. This study, in fact, further confirmation of the fact that a vaccinated individual does not transmit the infection in the same way as an unvaccinated individual (and this also emerged with the Delta variant, we talked about it HERE) and that the same vaccination can induce, in a family context, a sort of herd immunity: a bubble that manages to protect even those who have not been able to vaccinate, as in the case of families with children under the age of 12, therefore not immunizable. If you cannot get the vaccine, protecting other family members allows you to protect the whole community and this is also true when there are, within the nucleus, sick and particularly sick subjects fragile who were unable to receive the Covid vaccination for health reasons.
October 12, 2021 (change October 12, 2021 | 15:34)
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