Anti-spike antibody trajectories in individuals previously immunised with BNT162b2 or ChAdOx1 following a BNT162b2 booster dose

Abstract

The two most commonly-used SARS-CoV-2 vaccines in the UK, BNT162b2 (Pfizer-BioNTech) and ChAdOx1 nCoV-19 (Oxford-AstraZeneca), employ different immunogenic mechanisms. Compared to BNT162b2, two-dose immunisation with ChAdOx1 induces substantially lower peak anti-spike antibody (anti-S) levels and is associated with a higher risk of breakthrough infections. To provide preliminary indication of how a third booster BNT162b2 dose impacts anti-S levels, we performed a cross-sectional analysis using capillary blood samples from vaccinated adults (aged ≥18 years) participating in Virus Watch, a prospective community cohort study in England and Wales. Blood samples were analysed using Roche Elecsys Anti-SARS-CoV-2 S immunoassay. We analysed anti-S levels by week since the third dose for vaccines administered on or after September 1, 2021 and stratified the results by second dose vaccine type (ChAdOx1 or BNT162b2), age, sex and clinical vulnerability. Anti-S levels peaked at two weeks post-booster for BNT162b2 (22,185 U/mL; 95%CI: 21,406-22,990) and ChAdOx1 second dose recipients (19,203 U/mL; 95%CI: 18,094-20,377). These were higher than the corresponding peak antibody levels post-second dose for BNT162b2 (12,386 U/mL; 95%CI: 9,801-15,653, week 2) and ChAdOx1 (1,192 U/mL; 95%CI: 818-1735, week 3). No differences emerged by second dose vaccine type, age, sex or clinical vulnerability. Anti-S levels declined post-booster for BNT162b2 (half-life=44 days) and ChAdOx1 second dose recipients (half-life=40 days). These rates of decline were steeper than those post-second dose for BNT162b2 (half-life=54 days) and ChAdOx1 (half-life=80 days). Our findings suggest that peak anti-S levels are higher post-booster than post-second dose, but that levels are projected to be similar after six months for BNT162b2 recipients. Higher peak anti-S levels post-booster may partially explain the increased effectiveness of booster vaccination compared to two-dose vaccination against symptomatic infection with the Omicron variant. Faster waning trajectories post third-dose may have implications for the timing of future booster campaigns or four-dose vaccination regimens for the clinically vulnerable.

Duration of vaccine effectiveness against SARS-CoV-2 infection, hospitalisation, and death in residents and staff of long-term care facilities in England (VIVALDI): a prospective cohort study

“…Our findings are concordant with emerging clinical effectiveness data 26 and immunological data 27 , 28 showing the additional benefit of a booster dose, and with data from Israel showing reduced infection rates in residents in long-term care facilities in the period following roll-out of boosters. 29 Furthermore, three vaccine doses in unexposed residents appeared to offer equal or higher protection compared with previous exposure in the absence of vaccination, and we found rates of all three outcomes to be lowest in those with both previous exposure and vaccination.…”

Immune Cell Response during COVID-19 Infection and following SARS-CoV-2 Vaccination in Patients Admitted to Intensive Care Unit

“…Interestingly, despite the unchanged level of cellular response herein detected, the decreased level of IL-6 in vaccinated group especially in patients who have received the booster dose of vaccine, highlight the protective effect of vaccination against infection. Our findings are concordant with other clinical effectiveness and immunological data showing the benefic effect of a booster dosage and lower infection rates in long-term care facility patients in the time following the introduction of boosters [ 27 , 28 ].…”

Duration of vaccine effectiveness against SARS-CoV2 infection, hospitalisation, and death in residents and staff of Long-Term Care Facilities (VIVALDI): a prospective cohort study, England, Dec 2020-Dec 2021

“…Our findings are concordant with emerging clinical effectiveness data 26 and immunological data 27,28 demonstrating the additional benefit of a booster dose, and with data from Israel showing reduced infection rates in LTCF residents in the time period following roll-out of boosters. 29 Furthermore, three vaccine doses in unexposed residents appeared to offer equal or higher protection compared with prior exposure in the absence of vaccination, and we found rates of all three outcomes to be lowest in those with both prior exposure and vaccination.…”