Natural and hybrid immunity following four COVID-19 waves: A prospective cohort study of mothers in South Africa

Long term anti-SARS-CoV-2 antibody kinetics and correlate of protection against Omicron BA.1/BA.2 infection

“…These trials had found similar effect sizes of around five-fold reduction in risk of Alpha infections at anti-S antibody levels of 600 IU/mL (Feng et al, 2021), and a halving of hazard by 10-fold increase in anti-S titers for ancestral strain infections (Gilbert et al, 2022). Moreover our results are in line with available studies on Omicron BA.1/BA.2 subvariants which have also found binding antibody levels to be correlates of protection against infection using in-house immunoassays (Hertz et al, 2022;Zar et al, 2022). On the other hand, we did not find differences in the hazard of having an Omicron BA.1/BA.2 infection with anti-S antibody levels below or above a certain threshold in the non-infected vaccinated group, as opposed to results reported for Delta infections (Wei et al, 2021).…”

“…Using the same immunoassay as in this study and a cell-free Spike trimer-ACE2 binding-based surrogate neutralization assay (Fenwick et al, 2021), we did not observe any significant correlation between anti-S binding and neutralizing antibody levels against Omicron subvariants in uninfected participants, as opposed to previously infected participants (Zaballa et al, 2022). These results can be linked to growing evidence that hybrid immunity (infection plus vaccination) provides the strongest protection against Omicron subvariant infections (Altarawneh et al 2022, Zar et al 2022, Golddblatt 2022. This infection history-specificity thus warrants care in the interpretation of binding antibodies as correlates of protection against Omicron sub-lineages, and could be immunoassay-dependent.…”

“…Binding antibody measurements have been found to correlate with neutralization capacity against the ancestral SARS-CoV-2 strain at different degrees depending on time post infection/vaccination, and on immuno-assay (Earle et al, 2021;Goldblatt et al, 2022;L'Huillier et al, 2021). Evidence for their more general use as correlate of protection is mounting both from population-level (Earle et al, 2021;Goldblatt et al, 2022), as well as individual-level studies in the context of vaccine trials (Dimeglio et al, 2022b;Feng et al, 2021;Gilbert et al, 2022;Wei et al, 2021). These studies suggest that higher antibody measurements after infection and/or vaccination tend to reduce subsequent infection risk (Osman et al, 2021).…”

“…These studies suggest that higher antibody measurements after infection and/or vaccination tend to reduce subsequent infection risk (Osman et al, 2021). However, most of these studies focused on the ancestral SARS-CoV-2 strain and it is yet to be clarified whether these results robustly extend to the Omicron subvariants (Hertz et al, 2022;Zar et al, 2022).…”

Omicron B.1.1.529 variant infections associated with severe disease are uncommon in a COVID-19 under-vaccinated, high SARS-CoV-2 seroprevalence population in Malawi

“…For now, current evidence supports strong protection against severe COVID-19 from prior infection, 34,35 which is even better with hybrid immunity (prior infection plus vaccination). 36,37 The SARS-CoV-2 seroprevalence was generally high across all the seven districts surveyed in the current study, with higher seroprevalence in urban compared to rural areas, as reported in our blood donor serosurvey 10 and in other sub-Saharan African settings. 38 This is consistent with national COVID-19 data at the time of the study that reported 51% of confirmed cases in the country were from the cities of Blantyre and Lilongwe, 17 with a caveat that rural areas had relatively fewer SARS-CoV-2 testing sites.…”