If at the beginning of the Covid-19 pandemic it was believed that children were practically not affected by the coronavirus, now it is clear how wrong we were. Especially after the appearance of another strain – “omicron “, – when minors began to become infected even more often.
Scientists from the Clalit Research Institute in Israel, along with colleagues from Tel Aviv and Harvard Universities, have studied an important topic – indirect protection against SARS-CoV-2, which can be provided to a child by his vaccinated parents. The results of the work are published in the journal Science .
In Israel, as in Europe and the United States, younger age groups are the least covered by Covid-19 vaccination, although it has been allowed for teenagers over 12 years of age since May 2021, and children from five years old since November. Unlike the direct action of the mRNA vaccine from Pfizer and BioNTech, which has been actively studied in clinical trials and observational studies, the “indirect” action has not been given due attention, the authors of the article note.
They used data from Israel’s largest health organization to evaluate the indirect efficacy of BNT162b2 in unvaccinated children under 16 years of age from January 17 to March 28, 2021 (then alpha-dominated) and from July 11 to September 30 of the same year (wave “delta”). In the first group, cases were compared when parents were or were not vaccinated, in the second – when they were revaccinated or did not begin to do so.
“The early study period included 400,733 unvaccinated individuals (children and adolescents) from 155,305 households, which accounted for 2,116,306 person-weeks of follow-up. The mean age of the children was six years old, and 52% were male. Late period studies included 181,307 unvaccinated children from 76,621 different households, accounting for 1,089,191 person-weeks of follow-up. The average age was five years, 52% were boys,” the scientists write.
For the period from January to March last year, one vaccinated parent was associated with a 26.0% drop in the risk of contracting coronavirus in a child, while the fact of living in the same house with two vaccinated parents correlated with a decrease in the likelihood of getting Covid-19 by as much as 71 .7%.
“This effect was fairly uniform across all age groups and household sizes. Thus, the adjusted rate was 67.1% for a household of the third type, in which both parents were vaccinated, and 62.9% for a household of the seventh type and both vaccinated parents,” the researchers specified.
During the delta strain wave, one parent who had given two shots five months earlier helped reduce the child’s risk of infection by 20.8%, while two revaccinated parents reduced the risk of infection by 58.1%. In the case of adults themselves, two BNT162b2 vaccinations reduced the likelihood that they would catch Covid-19 by 94.4% (in the first period), three by 86.3% (in the second period of the study).
“Vaccination of parents significantly reduced the risk of SARS-CoV-2 infection in their children, although the effect was somewhat weaker in the later period. This can probably be considered a consequence of heterogeneity, since populations differ in composition.
But it is likely that the non-booster parents remained somewhat protected by the first two doses: this reduced the relative effect of the additional dose. It should be noted that the effect in the case of two vaccinated parents was significantly more noticeable than for one parent vaccinated in both periods (26.0% => 71.7%, 20.8% => 58.1%),” added scientists, summing up that even one unvaccinated adult remains a carrier of SARS-CoV-2 for those who live with him.
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