Study Finds Previous COVID-19 Infection Doesn’t Protect Children From Omicron

William A. Haseltine | Forbes | June 9, 2022

A new study found that less than 10 percent of children who contracted Covid-19 in 2020 or early 2021 developed neutralizing antibody titers against the Omicron variant of SARS-CoV-2. This finding reinforces the need to vaccinate children and teens against SARS-CoV-2 even with a prior infection. Not only are unvaccinated children significantly more likely to develop severe or fatal Covid-19 disease, but they can transmit Omicron to other highly vulnerable populations.

The study published in Nature was led by researchers at Harvard Medical School, Boston Children’s Hospital, and the U.S. Food and Drug Administration. It is now well established that prior infection does not protect adults from re-infection, but there is less research on children. The study assessed children’s ability to neutralize the Alpha, Beta, Gamma, Delta, and Omicron Covid-19 variants. Serum and plasma samples were collected from 3 independent pediatric disease cohorts: children younger than 5, children 5-11 years, and adolescents 12-21 years. None of the children and adolescents were vaccinated.

The researchers performed antibody profiling on the samples from 177 children and adolescents who were hospitalized with acute Covid-19 or MIS-C, or outpatient mild convalescent Covid-19. By using pseudovirion (a pseudovirus derived from SARS-CoV-2 but stripped of its virulence) neutralization assays, the researchers determined the antibody neutralization activity of the samples against the predominant SARS-CoV-2 WA1 strain and the 5 variants of concern. For the control group, the researchers used samples from 10 critically ill children who tested positive for seasonal coronaviruses before 2019. None of these controls demonstrated neutralization titers against Covid-19.

Children under the age of 5 who were hospitalized with severe acute Covid-19 were found to have lower neutralizing antibodies to SARS-CoV-2 variants compared with children older than 5. Convalescent pediatric Covid-19 and MIS-C cohorts showed higher neutralization titers than hospitalized acute Covid-19 patients. The researchers acknowledge that a limitation of the study is that it was able to test only for antibody responses, not other measures of immunity such as the production of T-cells.

All cohorts showed some loss of cross-neutralization against all variants, with the most pronounced loss against Omicron. In contrast to prior SARS-CoV-2 infection, children who were vaccinated twice demonstrated higher titers against Alpha, Beta, Gamma, Delta, and Omicron.

All cohorts showed some loss of cross-neutralization against all variants, with the most pronounced loss against Omicron. In contrast to prior SARS-CoV-2 infection, children who were vaccinated twice demonstrated higher titers against Alpha, Beta, Gamma, Delta, and Omicron.

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