Infections leave no antibody protection in children …

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SILVER SPRING / Maryland – Children who developed COVID-19 or multisystem inflammatory syndrome (MIS) after infection with a previous variant of SARS-CoV-2 had not developed adequate antibody protection against the omicron variant in a laboratory study.

A vaccination left after the entrance Nature communication (2022; DOI: 10.1038 / s41467-022-30649-1) exhibited some immunity.

Omicron is known to have deviated significantly further from the wild-type than previous variants of SARS-CoV-2. The consequences for adults are well known. The number of diseases reached a new peak in the omicron wave. However, many patients became only slightly ill, not least due to immunity to vaccinations or previous illnesses.

There is less information about infections in children. They were not in focus at the beginning of the pandemic because they usually only got a little sick, if at all. A special feature of children is the multisystem inflammatory syndrome (MIS), which is caused by an overreaction of the immune system and endangers the children’s lives in the short term due to a pumping weakness in the heart muscle.

Children were initially exempted from vaccinations. In the meantime, the vaccines (in Germany) have been approved since the age of 12. This age limit is likely to fall in the near future. Most parents are not willing because they think their children are protected by a possible (unnoticed, because asymptomatic) infection. According to laboratory results now presented by a team led by Surender Khurana from the US FDA in Silver Spring / Maryland, this could be a fallacy.

Researchers analyzed serum samples from 3 groups of children and adolescents for their ability to neutralize SARS-CoV-2 wild-type and variants alpha, beta, gamma, delta, and omicron. The experiments were performed with pseudoviruses, which have the properties of the individual variants, but which are not virulent.

The first group consisted of 62 children and adolescents who were treated in hospital for an acute illness from COVID-19. The 65 children and adolescents in the 2nd group had been in the hospital due to MIS. The third group of 50 children and adolescents had only been treated outpatient due to a mild illness. They had been infected 30 to 110 days before.

As expected, the neutralizing effect of the antibodies was weakest in the acutely ill children. The blood samples were taken from them before the defense system’s defense response had reached its peak.

Interestingly, the immune response in the youngest children with acute illness was the worst. There can be two reasons for this: On the one hand, blood samples from children under 5 years of age were taken much earlier after the onset of symptoms (median after 3 days instead of after 6 days in adolescents). The immune response to the virus had only just begun. On the other hand, the adolescent’s immune system could already be prepared for infection through previous infections with other corona viruses, allowing for a faster response.

In children with MIS, which typically occurs a few weeks after infection, and in children and adolescents treated outpatient, the neutralizing antibody effect against the wild type was strongest. This is probably because during the study period from April 2020 to March 2021, they were infected with the wild-type or alpha variant. Response to alpha through delta was barely diminished. These varieties differ slightly from the wild type.

The omicron variant, on the other hand, was hardly neutralized in the laboratory tests, which is probably related to the significant deviations from the wild type at the receptor binding site. Antibodies to these regions are most likely to prevent infection. The laboratory tests showed that they did not reach Omikron anywhere.

Khurana therefore warns parents not to trust that their children are infected in advance. She probably will not protect her children from infection with Omikron. The researchers also examined sera from 9 children who had received 1 or 2 doses of an mRNA vaccine. Here, too, the neutralizing effect was strongest against the wild type against which the vaccines were designed.

Against alpha and delta, the neutralizing effect was weakened by a factor of 2.5 and 2.1. The neutralizing effect was even lower by a factor of 25.2 against Omikron. According to Khurana, however, the titer could still be sufficient to at least prevent the children from becoming seriously ill. © rme / aerzteblatt.de

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