Seropersistence of SII-ChAdOx1 nCoV-19 (COVID-19 vaccine): 6-month follow-up of a randomized, controlled, observer-blind, phase 2/3 immuno-bridging study in Indian adults

ABSTRACT

AZD1222 (ChAdOx1 nCoV-19) is a replication-deficient adenoviral vectored coronavirus disease-19 (COVID-19) vaccine that is manufactured as SII-ChAdOx1 nCoV-19 by the Serum Institute of India Pvt Ltd following technology transfer from Oxford University/AstraZeneca. The non-inferiority of SII-ChAdOx1 nCoV-19 with AZD1222 was previously demonstrated in an observer-blind, phase 2/3 immuno-bridging study (trial registration: CTRI/2020/08/027170). In this analysis of immunogenicity and safety data 6 months post first vaccination (Day 180), 1,601 participants were randomized 3:1 to SII-ChAdOx1 nCoV-19 or AZD1222 (immunogenicity/reactogenicity cohort n = 401) and 3:1 to SII-ChAdOx1 nCoV-19 or placebo (safety cohort n = 1,200). Immunogenicity was measured by anti-severe acute respiratory syndrome coronavirus 2 spike (anti-S) binding immunoglobulin G and neutralizing antibody (nAb) titers. A decline in anti-S titers was observed in both vaccine groups, albeit with a greater decline in SII-ChAdOx1 nCoV-19 vaccinees (geometric mean titer [GMT] ratio [95% confidence interval (CI) of SII-ChAdOx1 nCoV-19 to AZD1222]: 0.60 [0.41–0.87]). Consistent similar decreases in nAb titers were observed between vaccine groups (GMT ratio [95% CI]: 0.88 [0.44–1.73]). No cases of severe COVID-19 were reported following vaccination, while one case was observed in the placebo group. No causally related serious adverse events were reported through 180 days. No thromboembolic or autoimmune adverse events of special interest were reported. Collectively, these data illustrate that SII-ChAdOx1 nCoV-19 maintained a high level of immunogenicity 6 months post-vaccination. SII-ChAdOx1 nCoV-19 was safe and well tolerated.

KEYWORDS:

• SARS-CoV-2
• COVID-19 vaccine
• SII-ChAdOx1 nCoV-19
• AZD1222 (ChAdOx1 nCoV-19)
• safety
• immunogenicity

Acknowledgments

We sincerely thank all the study participants and all the study team members. Medical editing assistance was provided by Laura Winton, BSc, and Craig O’Hare, PhD, of Ashfield MedComms, an Inizio company, which was in accordance with Good Publication Practice (GPP) 2022 guidelines (https://www.ismpp.org/gpp-2022; Ann Intern Med 2022 doi:10.7326/M22-1460) and funded by AstraZeneca.

Disclosure statement

The authors declare the following financial interests/personal relationships, which may be considered as potential competing interests: Cyrus S. Poonawalla is Chairman and Managing Director of Serum Institute of India Pvt. Ltd. Prasad S. Kulkarni, Chetanraj Bhamare, Abhijeet Dharmadhikari, Manish Gautam, Umesh Shaligram, Dhananjay Kapse, and Bhagwat Gunale are employed by Serum Institute of India Pvt. Ltd, which manufactures SII-ChAdOx1 nCoV-19 (COVID-19) vaccine. Chandrasekaran Padmapriyadarsini, Madhuri Thakar, Swarali N. Kurle, Nivedita Gupta, Samiran Panda, and Balram Bhargava are employed by ICMR. Johan Vekemans and Elizabeth J. Kelly are former employees of AstraZeneca and may hold AstraZeneca stock or stock options. Ashish Bavdekar, Madhu Gupta, Praveen Kulkarni, B.S. Garg, Nithya J. Gogtay, Muralidhar Tambe, Sanjay Lalwani, Kiranjit Singh, Renuka Munshi, Sushant Meshram, T.S. Selvavinayagam, Krishna Pandey, Devi Madhavi Bhimarasetty, S.R. Ramakrishnan, Chandrashekhar Budhawant, and Cyrille J. Bonhomme declare no potential conflicts of interest.

Author contributors

PSK, DK, BG, JV, US, CP, NG, SP, and CSP contributed to the study design and protocol development. PSK, DK, and BG accessed and verified the data. CJB, MT, and SNK led the immunogenicity experiments. CB contributed to the analysis. PSK, DK, and BG contributed to the manuscript preparation. The manuscript was finalized with considerable input from all authors. AB, MG, PK, BSG, NJG, MT, SL, KS, RM, SM, TSS, KP, DMB, and SRR contributed to data collection. EJK, US, and MG contributed to immunogenicity experiment oversight and supervision.

Data availability statement

Individual-level participant data will not be made available to others due to privacy concerns.

supplementary data

Supplemental data for this article can be accessed on the publisher’s website at https://doi.org/10.1080/21645515.2024.2304974.

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

The study was funded by SIIPL and the Indian Council of Medical Research. SIIPL funded the contract research organization and laboratory costs, while the site costs were funded by the Indian Council of Medical Research. The study vaccines were supplied by SIIPL and AstraZeneca.