Evaluation of Antibody Response to Heterologous Prime-Boost Vaccination with ChAdOx1 nCoV-19 and BNT162b2: An Observational Study

Davide Firinu; Andrea Perra; Marcello Campagna; Roberto Littera; Federico Meloni; Francesca Sedda; Maria Conti; Giulia Costanzo; Monica Erbi; Gianmario Usai; Carlotta Locci; Mauro Giovanni Carta; Riccardo Cappai; Germano Orrù; Stefano Del Giacco; Ferdinando Coghe; Luchino Chessa

doi:10.3390/vaccines9121478

Evaluation of Antibody Response to Heterologous Prime-Boost Vaccination with ChAdOx1 nCoV-19 and BNT162b2: An Observational Study

Vaccines (Basel). 2021 Dec 14;9(12):1478. doi: 10.3390/vaccines9121478.

Authors

Davide Firinu¹, Andrea Perra^{2

3}, Marcello Campagna¹, Roberto Littera^{3

4}, Federico Meloni¹, Francesca Sedda², Maria Conti¹, Giulia Costanzo¹, Monica Erbi¹, Gianmario Usai¹, Carlotta Locci¹, Mauro Giovanni Carta¹, Riccardo Cappai⁵, Germano Orrù¹, Stefano Del Giacco¹, Ferdinando Coghe⁵, Luchino Chessa^{1

3}

Affiliations

¹ Department of Medical Sciences and Public Health, University of Cagliari, 09100 Cagliari, Italy.
² Department of Biomedical Sciences, University of Cagliari, 09100 Cagliari, Italy.
³ Associazione per l'Avanzamento della Ricerca per i Trapianti O.d.V., Non Profit Organisation, 09100 Cagliari, Italy.
⁴ Medical Genetics, Department of Medical Sciences and Public Health, University of Cagliari, 09100 Cagliari, Italy.
⁵ Laboratory Clinical Chemical Analysis and Microbiology, University Hospital of Cagliari, 09042 Cagliari, Italy.

Abstract

In several countries, thrombotic events after vaccination with ChAdOx1 nCoV-19 have led to heterologous messenger RNA (mRNA) boosting. We tested the antibody response to SARS-CoV-2 spike protein four weeks after heterologous priming with the ChAdOx1 (ChAd) vector vaccine followed by boosting with BNT162b2(ChAd/BNT), comparing data of homologous regimen (BNT/BNT, ChAd/ChAd) subjects positive for SARS-CoV-2 after the first dose of BNT162b2 (BNT1dose/CoV2) and convalescent COVID-19.

Methods: healthy subjects naïve for SARS-CoV-2 infection were assessed for serum IgG anti-S-RBD response 21 days after priming (T1), 4 (T_FULL) and 15 (T_15W) weeks after booster dose.

Results: The median IgG anti-S-RBD levels at T_FULL of Chad/BNT group were significantly higher than the BNT/BNT group and ChAd/ChAd. Those of BNT/BNT group were significantly higher than ChAd/ChAd. IgG anti-S-RBD of BNT1dose/CoV2 group were similar to BNT/BNT, ChAd/BNT and ChAd/Chad group. The levels among COVID-19 convalescents were significantly lower than ChAd/BNT, BNT/BNT, ChAd/Chad and BNT1dose/CoV2. The proportion of subjects reaching an anti-S-RBD titer >75 AU/mL, correlated with high neutralizing titer, was 94% in ChAd/BNT and BNT/BNT, 60% in BNT1dose/CoV2, 25% in ChAd/ChAd and 4.2% in convalescents. At T_15W the titer of ChAd/BNT was still significantly higher than other vaccine schedules, while the anti-S-RBD decline was reduced for ChAd/ChAd and similar for other combinations.

Conclusion: Our data highlight the magnitude of IgG anti-S-RBD response in ChAd/BNT dosing, supporting the current national guidelines for heterologous boosting.

Keywords: BNT162b2; COVID-19; ChAdOx1; heterologous; immunogenicity; vaccination.

Abstract

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