Cumulative incidence of SARS‐CoV‐2 infection in the general population of the Valencian Community (Spain) after the surge of the Omicron BA.1 variant

Abstract

Studies investigating the cumulative incidence of and immune status against SARS‐CoV‐2 infection provide valuable information for shaping public health decision‐making. A cross‐sectional study on 935 participants, conducted in the Valencian Community (VC), measuring anti‐SARS‐CoV‐2‐receptor binding domain‐RBD‐total antibodies and anti‐Nucleocapsid (N)‐IgGs via electrochemiluminescence assays. Quantitation of neutralizing antibodies (NtAb) against ancestral and Omicron BA.1 and BA.2 variants and enumeration of SARS‐CoV‐2‐S specific‐IFNγ‐producing CD4+ and CD8+ T cells was performed in 100 and 137 participants, respectively. The weighted cumulative incidence was 51.9% (95% confidence interval [CI]: 48.7–55.1) and was inversely related to age. Anti‐RBD total antibodies were detected in 97% of participants; vaccinated and SARS‐CoV‐2‐experienced (VAC‐ex; n = 442) presented higher levels (p < 0.001) than vaccinated/naïve (VAC‐n; n = 472) and nonvaccinated/experienced (UNVAC‐ex; n = 63) subjects. Antibody levels correlated inversely with time elapsed since last vaccine dose in VAC‐n (Rho, −0.52; p < 0.001) but not in VAC‐ex (rho −0.02; p = 0.57). Heterologous booster shots resulted in increased anti‐RBD antibody levels compared with homologous schedules in VAC‐n, but not in VAC‐ex. NtAbs against Omicron BA.1 were detected in 94%, 75%, and 50% of VAC‐ex, VAC‐n and UNVAC‐ex groups, respectively. For Omicron BA.2, the figures were 97%, 84%, and 40%, respectively. SARS‐CoV‐2‐S‐reactive IFN‐γ T cells were detected in 73%, 75%, and 64% of VAC‐ex, VAC‐n and UNVAC‐ex, respectively. Median frequencies for both T‐cell subsets were comparable across groups. In summary, by April 2022, around half of the VC population had been infected with SARS‐CoV‐2 and, due to extensive vaccination, displayed hybrid immunity.

Seroprevalence of Anti-SARS-CoV-2 Antibodies Following the Omicron BA.1 Wave

“…Our study also found that the correlate of infection-induced seroprevalence only, i.e., anti-N antibodies, decreased with age. This age-related finding is in accordance with post-BA.1 seroprevalence studies: children, adolescents, and young adults were the least vaccinated but most infected age subgroups during the Omicron BA.1 wave [ 28 , 29 , 32 , 34 , 35 , 43 ]. In most countries, the education systems functioned with few restrictions during this period, and children and adolescents were socialising to almost the same extent as before the COVID-19 pandemic.…”

A machine learning model for predicting serum neutralizing activity against Omicron SARS‐CoV‐2 BA.2 and BA.4/5 sublineages in the general population

“…Anti-SARS-CoV-2 nucleocapsid protein (N) IgG antibodies and anti-RBD total antibodies were measured by the Elecsys ® Anti-SARS-CoV-2 N IgG assay and the Elecsys ® Anti-SARS-CoV-2 S assay (Roche Diagnostics), as previously reported. 17 NtAbs against Omicron BA.2 and BA4/5 were measured using a GFP-expressing vesicular stomatitis virus pseudotyped with the Omicron BA.2 and BA.4/5 S protein, as described elsewhere. [18][19][20]…”

Antibody‐dependent NK‐cell and neutralizing antibody responses against the Spike protein of Wuhan‐Hu‐1 and Omicron BA.1 SARS‐CoV‐2 variants in vaccinated experienced and vaccinated naïve individuals

“…A total of 50 individuals (median age, 44.5 years; range, 11-85; 25 males) randomly selected from 931 participants among the general population recruited in a SARS-CoV-2 cumulative incidence study conducted at the Valencian Community (Spain) in April, 2022 were included in the study. 21…”