Oxford’s COVID-19 Vaccine Induces Strong Immune Responses in Early-Stage Trial

July 20, 2020

The AZD1222 vaccine, made from a common cold virus present in chimpanzees, produced rapid neutralizing antibody levels against the SARS-CoV-2 virus.

An ongoing clinical trial led by Oxford University investigating a potential severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine against the novel coronavirus disease 2019 (COVID-19) reported encouraging early results, according to investigators.1

Published in The Lancet, the phase 1/2 COV001 study’s investigators found that a single dose of the AZD1222 vaccine, previously known as ChAdOx1 nCoV-19, prompted effective immune and T cell responses. More specifically, the dose resulted in a 4-fold increase in antibodies for SARS-CoV-2 in 95% of participants 1 month following receiving the vaccine, and all participants showed a T cell response that remained 2 months after being administered AZD1222.2

AZD1222 was cocreated by the University of Oxford and its company, Vaccitech, through a replication-deficient chimpanzee viral vector based on a weakened version of adenovirus, a common cold virus, which causes infections in chimpanzees. Adenovirus also houses genetic material of the SARS-CoV-2 virus spike protein.2

The phase 1/2 trial, which incorporated 1077 healthy adult participants, correlated the vaccine with strong antibody and T cell immune responses up to day 56 on the trial, which plans to evaluate participants for 364 days.1

Adding to these interim results, investigators also evaluated a second dose of the vaccine in a sub-group of 10 participants and found an even stronger immune response.1

The blinded, multicenter, randomized controlled phase 1/2 COV001 trial assessed single dose AZD1222 in individuals between the ages of 18 to 55 years old against a comparator meningococcal conjugate vaccine called Men ACWY. In addition to the single dose, 10 adults also received 2 doses of AZD1222 1 month apart. Researchers drew blood samples and engaged participants in clinical assessments for safety and immunogenicity at day 0 and 28 so far, with plans for day 184 and 364 assessments as well. 2

Investigators used the MNA80 assay to deduce neutralizing activity against the virus, of which 91% of the study participants demonstrated. Data also found that neutralizing antibody levels expressed similarities to those noted in convalescent COVID-19 patients.2

Adverse events (AEs) related to administration of AZD1222 reflected previous studies and included injection site pain and tenderness, mild-to-moderate headache, fatigue, chills, feverishness, malaise and muscle ache, with no serious events reported.2

Following the study results, researchers intend to conduct follow up clinical studies in older adult populations, who present higher rates of comorbidities and therefore are at increased risk of suffering severe complications from the SARS-CoV-2 virus.1

“We are encouraged by the Phase I/II interim data showing AZD1222 was capable of generating a rapid antibody and T-cell response against SARS-CoV-2,” Mene Pangalos, executive vice president of BioPharmaceuticals R&D, said in a statement.2 “While there is more work to be done, today’s data increases our confidence that the vaccine will work and allows us to continue our plans to manufacture the vaccine at scale for broad and equitable access around the world.”


  1. COVID-19 vaccine AZD1222 showed robust immune responses in all participants in Phase I/II trial. News Release. AstraZeneca; July 20, 2020. Accessed July 20, 2020. https://www.astrazeneca.com/content/astraz/media-centre/press-releases/2020/covid-19-vaccine-azd1222-showed-robust-immune-responses-in-all-participants-in-phase-i-ii-trial.html.
  2. The Lancet: UK’s vaccine against SARS-CoV-2 is safe and induces an immune reaction. News Release. EurekAlert; July 20, 2020. Accessed July 20, 2020. https://www.eurekalert.org/pub_releases/2020-07/tl-tlu072020.php.