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

Hum Vaccin Immunother. 2024 Dec 31;20(1):2304974. doi: 10.1080/21645515.2024.2304974. Epub 2024 Mar 21.

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: AZD1222 (ChAdOx1 nCoV-19); COVID-19 vaccine; SARS-CoV-2; SII-ChAdOx1 nCoV-19; immunogenicity; safety.

Publication types

  • Randomized Controlled Trial
  • Clinical Trial, Phase II
  • Clinical Trial, Phase III
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Antibodies, Viral
  • COVID-19 Vaccines / adverse effects
  • COVID-19* / prevention & control
  • ChAdOx1 nCoV-19*
  • Follow-Up Studies
  • Humans
  • Immunogenicity, Vaccine
  • Immunoglobulin G

Substances

  • ChAdOx1 nCoV-19
  • COVID-19 Vaccines
  • Immunoglobulin G
  • Antibodies, Viral

Grants and 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.