Preschool and school children in Germany have been infected with SARS-CoV-2, the virus that causes Covid-19, three to four times more than reported via PCR testing during the second wave, a study has revealed.

Preschool children showed an antibody frequency of 5.6 per cent from October 2020 to February 2021. Among school children who were tested between November 2020 and February 2021, the figure was as high as 8.4 per cent.

Overall, the antibody frequency at the end of the second wave (January and February 2021) was about eight times higher compared to the end of the first wave (April to July 2020), revealed the study published in the journal Med.

“Children are often said to be less likely infected compared to adults. However, the data for this assumption is sparse. The results of our study clearly show that both preschool and school children are susceptible to SARS-CoV-2 infection,” explained Anette-Gabriele Ziegler, from Helmholtz Zentrum Munchen, German Research Centre for Environmental Health, Munich-Neuherberg, Germany.

“To better control infections in this population group, adequate measures to contain the spread of the virus in kindergartens and schools could be helpful,” Ziegler said.

The significant increase is the result of higher exposure to the virus in the fall and winter, school openings and novel more infectious virus variants, said the researchers, adding that more infections compared to reported cases “may be due to asymptomatic cases in childhood”.

Among the 446 children who tested positive in the second wave, the proportion of antibody-positive children without symptoms was 68 per cent among pre-schoolers. Among school-aged children, it was 51.2 per cent.

The children were part of the screening study “Fr1da”, led by Ziegler in Bavaria, to identify early stage of Type-1 diabetes. No association between Type-1 diabetes and Covid-19 was found in the children.

During the first wave in Germany in spring 2020, the team detected a SARS-CoV-2 antibody frequency of 0.87 percent in the children who took part in the study. This means that six times more children in Bavaria were infected with the coronavirus than reported via PCR tests, the researchers stated.