In SARS-CoV-2 unvaccinated cases, Omicron infection shows limited cross-reactive neutralization against other variants
A group from Gladstone Institutes, San Francisco, CA, USA, etc. has reported that infection with Omicron variant in unvaccinated individuals may not elicit effective cross-neutralizing antibodies against other variants. In vaccinated individuals, however, Omicron infection effectively induces immunity against itself and enhances protection against other variants. https://www.medrxiv.org/content/10.1101/2022.01.13.22269243v1.full-text To determine humoral immune responses induced by infection with the three different strains, sera from infected mice and tested their neutralization efficiency against SARS-CoV-2 strains were collected: WA1, Alpha, Beta, Delta, and Omicron. Efficient virus neutralization was defined by more than 50% reduction in plaque forming units at the lowest serum dilutions. Sera from Delta-infected mice showed the broadest cross-variant neutralization, effectively neutralizing all the strains except Beta. By contrast, while Omicron infection effectively neutralized Omicron itself, it exhibited limited (80%) against all strains, including Omicron as shown below.
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