SARS-CoV-2 Omicron Variant Neutralization in Serum from Vaccinated and Convalescent Persons

Omicron Genetic and Clinical Peculiarities That May Overturn SARS-CoV-2 Pandemic: A Literature Review

“…Humoral immunity escape may also be linked to a higher risk of reinfection (defined as a repeat positive test at least 90 days after an earlier positive test) in individuals previously infected with a different strain [23]. This is also supported by preliminary findings from several laboratories in which sera from previously infected, unvaccinated individuals, did not neutralise the Omicron variant [29]. Whether subneutralising antibodies (from the previous infection with other VOC or vaccines) could facilitate the Omicron entry in the cells by their Fc receptor through the known antibody-dependent enhancement (ADE) mechanism remains to be investigated.…”

“…In South Africa, two doses of BNT162b2 were associated with a 33% effectiveness against SARS-CoV-2 infection and 70% effectiveness against COVID-19 hospitalisation during the Omicron surge [76]. Moreover, neutralising antibodies titre against Omicron variant were significantly lower when compared to titres against other VOCs [29]. In line with these findings, a recent analysis suggested that primary vaccination was insufficient to effectively neutralise Omicron spike proteins, allowing this VOC an efficient escape from humoral immunity [77].…”

Milder disease with Omicron: is it the virus or the pre-existing immunity?

“…The Omicron variant of SARS-CoV-2 escapes immunity generated by vaccines and previous infections 1 , 2 yet seems to have some unexpected advantages over the other variants we have experienced so far. Firstly, and most importantly, strong evidence is emerging that the disease induced by infection with Omicron is considerably milder at the population level (Fig.…”

“…Studies looking at neutralizing immunity against Omicron showed that although Omicron can escape this immunity, it is essentially a numbers game. Increased levels of neutralizing antibodies owing to booster vaccines or a combination of previous infection and vaccination counteract viral escape, so that antibody neutralization against Omicron in these groups is more or less equivalent to the neutralization seen against variants such as Delta in those who are fully vaccinated but not boosted 1 , 2 . Furthermore, the levels of antibody-mediated immunity required for protection against severe disease are much lower and may be achieved by vaccination alone, even in the absence of boosters 8 .…”

Genomic monitoring unveils a high prevalence of SARS-CoV-2 Omicron variant in vaccine breakthrough cases

“…The countries that have reached or surpassed this percentage (England, Israel, and Brazil) have high infection rates since the emergence of Omicron 20,21 . In our state, 74.9 % of the vaccination coverage has currently been reached with two doses, but our work demonstrated breakthrough infection by Omicron with the high viral load even in double or triple vaccinated individuals.…”