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Scientists welcome Oxford Covid-19 vaccine efficacy data

Image: D Wells [CC BY-SA 4.0], via Wikimedia Commons

Vaccine up to 90 per cent effective with the right dosage, interim trial data suggest

Scientists have welcomed news that a Covid-19 vaccine developed by the University of Oxford and pharmaceutical giant AstraZeneca could be up to 90 per cent effective.

Interim data from phase 3 clinical trials indicated that the candidate vaccine, ChAdOx1 nCoV-2019, was 70.4 per cent effective overall, but with tests showing that the vaccine was 90 per cent effective if administered at a half dose and then at a full dose.

Such dosing could potentially provide better protection while also making the vaccine go further. The UK has pre-ordered 100 million doses of the vaccine.

Andrew Pollard, director of the Oxford Vaccine Group and chief investigator of the Oxford vaccine trial, said “if this dosing regime is used, more people could be vaccinated with planned vaccine supply”. 

Of those who had received the vaccine, there were no hospitalised or severe cases, the university announced on 23 November.

Based on an observed reduction in asymptomatic infections in vaccinated volunteers, there were also early indications that the vaccine could reduce virus transmission rather than just prevent illness.

“The announcement today takes us another step closer to the time when we can use vaccines to bring an end to the devastation caused by SARS-CoV-2,” said Sarah Gilbert, a professor of vaccinology, who led the development of the vaccine at the university’s Jenner Institute (pictured). “We will continue to work to provide the detailed information to regulators.”

The results come after Pfizer and Moderna announced an efficacy rate of around 95 per cent for the companies’ own phase 3 clinical trials.

Unlike their vaccines, which have to be stored at much colder temperatures, the Oxford vaccine can be stored at fridge temperature, meaning it can be distributed using existing logistics.

“The really good news is twofold,” said Stephen Evans, a professor at the London School of Hygiene and Tropical Medicine (LSHTM). “Firstly, the vaccine can be stored in ordinary refrigerators, which helps in high-income countries, but is of enormous importance for low-income countries.

“Secondly, the manufacturers and Oxford are committed to making it as easy as possible, through the WHO Covax agreements, for the vaccine to reach low- and middle-income countries with their pledge to provide the vaccine at [a low] cost to such countries, not just for the duration of the pandemic, but indefinitely.”

Peter Horby, a professor of emerging infectious diseases and global health at the University of Oxford, said “we can clearly see the end of the tunnel now”.

But he added a note of caution: “Although no serious reactions were reported in people who got the Oxford vaccine, we do need to await the full safety data and to monitor safety of all vaccines carefully if and when they are rolled out. The reported efficacy of 70 per cent is an interim measure and as more data accrue we will get a better idea of the protection it affords.”

The news follows a report from the Social Science in Humanitarian Action Platform–a partnership between the Institute of Development Studies, Anthrologica and LSHTM–which warned that successful take-up of a Covid-19 vaccine would rely on transparency and trust, not just on combatting misinformation.

“It is very welcome news that at last vaccines have been identified that have impact in containing Covid-19,” said Melissa Leach, director of the IDS.

“However, the success of the vaccines in stopping this global pandemic rely on governments investing as much in vaccine confidence as deployment. As our research shows, building trust in government and the public health response will be critical components to the take-up of the Covid-19 vaccine.”

The report identifies a number of strategies and approaches that could help build vaccine confidence. These include exercising transparency as far as possible in trial processes, “imaginative and compelling” communications, being honest about uncertainties, co-designing and discussing vaccination strategies with citizens, carrying out qualitative research of vaccine hesitancy and confidence, and rapidly increasing communication, dialogue and planning with communities.

The news also followed an announcement by the Good Law Project that it was seeking a judicial review of three Covid appointments, including that of Kate Bingham as a head up Britain’s vaccine taskforce. The project said that “the roles were not openly advertised: there was no proper recruitment process”.