Oxford Covid-19 vaccine shows sustained protection of 76% during 3-month interval until second dose
- Wits University
Researchers at the University of Oxford have today published in Preprints with The Lancet an analysis of further data from the ongoing trials of the vaccine.
The Vaccines and Infectious Diseases Analytics Research Unit (VIDA) at Wits University runs the South African Oxford Covid-19 vaccine trial. Professor Shabir Madhi, Executive Director of Wits VIDA and Dean of the Faculty of Health Sciences at the University, leads these trials and he is a co-author in the Preprints.
In releasing the data regarding sustained protection of 76% during the 3-month interval until the second dose, scientists at Oxford reveal that the vaccine efficacy is higher at longer prime-boost intervals, and that a single dose of the vaccine is 76% effective from 22- to up to 90-days post vaccination. The analyses reveal:
- Single standard dose efficacy from day 22 to day 90 post vaccination of 76% with protection not falling in this three-month period
- After the second dose vaccine efficacy from two standard doses is 82.4% with the 3-month interval being used in the UK. (82.4% effective, with a 95% confidence interval of 62.7% - 91.7% at 12+ weeks)
- Data supports the 4-12 week prime-boost dosing interval recommended by many global regulators
- Analyses of PCR positive swabs in UK population suggests vaccine may have substantial effect on transmission of the virus with 67% reduction in positive swabs among those vaccinated
In this preprint, which is currently under review at The Lancet, they report on an analysis of additional data to include information from the trial up to the 7th December 2020, which includes a further 201 cases of primary symptomatic COVID-19 (332 cases from 131 reported in previously), they report that the effect of dosing interval on efficacy is pronounced, with vaccine efficacy rising from 54.9% with an interval of less than six weeks to 82.4% when spaced 12 or more weeks apart.
They also detail that a single standard dose of the vaccine is 76% effective at protecting from primary symptomatic COVID-19 for the first 90 days post vaccination, once the immune system has built this protection 22 days after the vaccination, with the protection showing little evidence of waning in this period.
Professor Andrew Pollard, Chief Investigator of the Oxford Vaccine Trial, and co-author of the paper, says, "These new data provide an important verification of the interim data that was used by more than 25 regulators including the MHRA and EMA to grant the vaccine emergency use authorisation. It also supports the policy recommendation made by the Joint Committee on Vaccination and Immunisation (JCVI) for a 12-week prime-boost interval, as they look for the optimal approach to roll out, and reassures us that people are protected from 22 days after a single dose of the vaccine."
The exploratory analyses presented in this preprint paper suggest that it is the dosing interval and not the dosing level which has a great impact on the efficacy of the vaccine. This is in line with previous research supporting greater efficacy with longer prime-boost intervals done with other vaccines such as influenza, Ebola and malaria.
The authors also report further on the potential for the vaccine to reduce transmission of the virus, based on swabs obtained from volunteers in the UK arms of the trial with a 67% reduction after the first dose of the vaccine.
They also hope to report data regarding the new variants in the coming days, and expect the findings to be broadly similar to those already reported by fellow vaccine developers.
About the Oxford COVID-19 vaccine
ChAdOx1 nCoV-19, now known as AZD1222 co-invented by the University of Oxford and its spin-out company, Vaccitech, is being trialled by the University’s Jenner Institute and Oxford Vaccine Group. The team started working to develop a vaccine against coronavirus in January 2020.
Developed at the Jenner Institute, the recombinant adenovirus vector ChAdOx1 nCoV-19 uses a viral vector based on a weakened version of the common cold virus (adenovirus) containing the genetic material of SARS-CoV-2 spike protein. After vaccination, the surface spike protein is produced, which primes the immune system to attack COVID-19 if it later infects the body.
Over 50,000 people to date have taken part in clinical trials of The ChAdOx1 nCoV-19 vaccine sponsored by the University of Oxford and AstraZeneca, and many more have received the vaccine through public vaccination programmes following emergency use licensure. It has been shown to be safe and well tolerated, although it can cause temporary side effects, such as a temperature, flu-like symptoms, headache or sore arm.
The potential vaccine entered Phase III clinical trials in May to study safety and efficacy in healthy volunteers. In total, nearly 24,000 volunteers have joined the University of Oxford sponsored trial, in sites around the UK (approximately 12,000 volunteers), Brazil (approximately 10,000 volunteers) and South Africa (approximately 2,000 volunteers). Interim efficacy and safety data were published in The Lancet in December, including an extensive safety database of over 74,000 ‘person months’ of safety data follow-up.
Our partners, AstraZeneca, have committed to delivering billions of doses of its COVID-19 vaccine across the globe in a broad, equitable, and timely way at no profit during the pandemic. This includes an agreement with the European Commission to supply up to 400 million doses, starting in early 2021 following the regulatory approval from the European Medicines Agency, with tens of millions of doses due to be supplied in February and March.
Not for profit information
As part of the agreement between University of Oxford and AstraZeneca, the vaccine will be supplied on a not-for-profit basis for the duration of the pandemic and in perpetuity for low- and middle-income countries, with any future royalties received by the University of Oxford being re-invested in the medical sciences.
This trial is funded by the National Institute for Health Research, UK Research and Innovation, the Bill & Melinda Gates Foundation, the Lemann Foundation, and the South African Medical Research Council. We are grateful to the NIHR infrastructure provided through the NIHR Biomedical Research Centres and the NIHR Clinical Research Network at the UK study sites.