Just over half (50.9%) of primary school children had antibodies against the coronavirus between 6 and 17 December, right before the outbreak of the fifth wave in Belgium, according to research by the Sciensano national health institute and KU Leuven.
The percentage in December, right before the start of the Omicron wave, was roughly double the previous measurement in September-October 2021, when 26.6% of primary school children had antibodies. This means that a large number of primary school children contracted a Covid-19 infection with the Delta variant in the fourth wave that started in October 2021.
"Our findings show that the Delta variant of the coronavirus caused a larger virus circulation among children than previous variants," Sciensano researcher Els Duysburgh said in a press release.
During the fifth and final tests in December 2021, when children under 12 were not yet eligible for vaccination, 50.9% of the 432 pupils tested had antibodies against the coronavirus. The sample is representative of all pupils in Belgium.
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"This large virus circulation was also observed in the general population during the fourth wave, despite high vaccination coverage in this group," she added. "This trend appears to be reinforced with the current Omicron variant."
Sciensano also found striking regional differences: in Wallonia, 58.6% of pupils had antibodies, compared to 48.2% in Flanders and 47.3% in Brussels.
In a survey accompanying the study, 26.9% of pupils reported having had a confirmed Covid-19 infection since the start of the pandemic. For 15.5% of pupils, this occurred between October and December.
Even though half of primary school children already contracted Covid-19, only one in four reported an infection that was confirmed by PCR or rapid test, meaning that many children with antibodies do not even know they have been infected.
Children who come into contact with the coronavirus rarely become severely ill, and none of the participating children reported to have been hospitalised because of Covid-19.
