AstraZeneca has reported positive data from the Phase I/II COV001 clinical trial of a potential Covid-19 vaccine, developed by the University of Oxford and licensed to the company.

Early data showed that the vaccine candidate was tolerated and generated strong immune responses in all evaluated participants. Findings have been published in The Lancet journal.

Led by the university, the blinded, multi-centre, randomised controlled trial involved 1,077 healthy adult volunteers aged 18 to 55 years. It compared a single dose of AZD1222 against meningococcal conjugate vaccine, MenACWY.

In addition, ten participants were given two AZD1222 doses one month apart.

According to the study results, a single dose of AZD1222 led to a four-fold increase in antibodies to the SARS-CoV-2 virus spike protein in 95% of subjects one month following vaccination.

Furthermore, a T-cell response that peaked by day 14 and maintained two months after injection was observed in all participants.

Researchers also reported neutralising activity against SARS-CoV-2 one month after injection in 91% of participants and in all participants who received two doses.

The levels of neutralising antibodies in participants who were given either one or two doses of the Oxford vaccine were found to be in a similar range to those observed in convalescent Covid-19 patients.

In participants who received AZD1222, common transient local and systemic reactions were temporary injection site pain and tenderness, fatigue, chills, mild-to-moderate headache, feverishness, malaise and muscle ache.

These early safety responses were comparable to prior studies and other adenoviral vector vaccines. The researchers did not report any serious adverse events with AZD1222.

Oxford Vaccine Trial chief investigator professor Andrew Pollard said: “The interim Phase I/II data for our coronavirus vaccine shows that the vaccine did not lead to any unexpected reactions and had a similar safety profile to previous vaccines of this type.

“The immune responses observed following vaccination are in line with what we expect will be associated with protection against the SARS-CoV-2 virus, although we must continue with our rigorous clinical trial programme to confirm this.”

Pollard added that the strongest immune response in subjects who received two doses could indicate a good vaccination strategy.

Currently, late-stage Phase II/III trials are ongoing in the UK, Brazil and South Africa. Studies are also set to launch in the US.

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