Ad5‐nCoV booster and Omicron variant breakthrough infection following two doses of inactivated vaccine elicit comparable antibody levels against Omicron variants

Abstract

Little information is available for antibody levels against SARS‐CoV‐2 variants of concern induced by Omicron breakthrough infection and a third booster with an inactivated vaccine (InV) or Ad5‐nCoV in people with completion of two InV doses. Plasma was collected from InV pre‐vaccinated Omicron‐infected patients (OIPs), unvaccinated OIPs between 0 and 22 days, and healthy donors (HDs) 14 days or 6 months after the second doses of an InV and 14 days after a homogenous booster or heterologous booster of Ad5‐nCoV. Anti‐Wuhan‐, Anti‐Delta‐, and Anti‐Omicron‐receptor binding domain (RBD)‐IgG titers were detected using enzyme‐linked immunosorbent assay. InV pre‐vaccinated OIPs had higher anti‐Wuhan‐, anti‐Delta‐, and anti‐Omicron‐RBD‐IgG titers compared to unvaccinated OIPs. Anti‐Wuhan‐RBD‐IgG titers sharply increased in InV pre‐vaccinated OIPs 0–5 days postinfection (DPI), while the geometric mean titers (GMTs) of anti‐Delta‐ and anti‐Omicron‐RBD‐IgG were 3.3‐fold and 12.0‐fold lower. Then, the GMT of anti‐Delta‐ and anti‐Omicron‐RBD‐IgG increased to 35 112 and 28 186 during 11–22 DPI, about 2.6‐fold and 3.2‐fold lower, respectively, than the anti‐Wuhan‐RBD‐IgG titer. The anti‐Wuhan‐, anti‐Delta‐, and anti‐Omicron‐RBD‐IgG titers declined over time in HDs after two doses of an InV, with 25.2‐fold, 5.6‐fold, and 4.5‐fold declination, respectively, at 6 months relative to the titers at 14 days after the second vaccination. Anti‐Wuhan‐, anti‐Delta‐, and anti‐Omicron‐RBD‐IgG titers elicited by a heterologous Ad5‐nCoV booster were significantly higher than those elicited by an InV booster, comparable to those in InV pre‐vaccinated OIPs. InV and Ad5‐nCoV boosters could improve humoral immunity against Omicron variants. Of these, the Ad5‐nCoV booster is a better alternative.

Effectiveness of a booster dose of COVID-19 vaccines during an outbreak of SARS-CoV-2 Omicron BA.2.2 in China: A case–control study

“… 27 , 28 Additionally, homogenous booster vaccination (same as the primary vaccine) and heterologous booster vaccination (third dose with an Ad5-nCoV or recombinant protein vaccine) following a two-dose regimen of inactivated vaccines were included in our study. 24 , 29 …”

Immunity against Delta and Omicron variants elicited by homologous inactivated vaccine booster in kidney transplant recipients

“…Antibody titers were determined using an enzyme-linked immunosorbent assay (ELISA) as previously reported ( 17 ). Briefly, 96-well ELISA plates were coated with proper concentrations of recombinant viral antigens including SARS-CoV-2 ancestral strain-spike trimer (Dongkang Biotech, China, 50 ng/well), ancestral strain-NP (Dongkang Biotech, China, 100 ng/well), ancestral strain-RBD (Dongkang Biotech, China, 180 ng/well), Delta variants-RBD (Fapon Biotech, China, 120 ng/well), and Omicron variants-RBD (Fapon Biotech, China, 180 ng/well) overnight and blocked by adding 100 μL of 5% milk blocking solution in each well of ELISA plate.…”

“…Lastly, the optical density (OD) value was measured at 450nm using a microplate absorbance reader (Tecan Sunrise, Switzerland). Antibody endpoint titers were determined according to the highest dilution, which gave an OD value higher than the mean + 3SD OD values of 3 serum pools from 45 already stored serums at the same dilution collected from healthy individuals in the year 2016 ( 17 ).…”

Effectiveness of a booster dose of COVID-19 vaccines during an outbreak of SARS-CoV-2 Omicron BA.2 in China: A case-control study

“…We divided all participants into four groups: unvaccinated (zero doses, or first dose<14 days from time of last exposure), partial vaccination (one-dose inactivated vaccine or two-dose recombinant protein vaccine, with the last dose of vaccination >14 days from the time of last exposure), full vaccination (one-dose Ad5-nCoV vaccine or two-dose inactivated vaccine or three-dose recombinant protein vaccine, with the last dose of vaccination >14 days from the time of last exposure), and booster vaccination (three-dose of any COVID-19 vaccine, or two-dose Ad5-CoV vaccine, or three-dose recombinant protein vaccine, or two-dose any inactivated vaccine with a one-dose Ad5-CoV vaccine/recombinant protein vaccine, with the last dose of vaccination >14 days from the time of last exposure) [27,28] . Additionally, homogenous booster vaccination (same as the primary vaccine) and heterologous booster vaccination (third dose with an Ad5-nCoV or recombinant protein vaccine) following a two-dose regimen of inactivated vaccines were included in our study [24,29] .…”