The Oxford COVID-19 vaccine has been found to be safe, with only three out of 23,745 participants over a median of 3.4 months experiencing serious adverse events that were possibly related to a vaccine.
All three participants have recovered or are recovering, and remain in the trial, Prof Andrew pollard from the University of Oxford, who is the lead author of the study, said while addressing a virtual media conference following the publication of the interim results of the Oxford COVID-19 vaccine trials in the lancet on Tuesday.
The results are the first full peer-reviewed efficacy result to be published for an Oxford COVID-19 vaccine. According to the results, the vaccine protects against symptomatic disease in 70 per cent of cases, with vaccine efficacy of 62 per cent for those given two full doses, and 90 per cent for those given a half, and then a full dose.
The Oxford vaccine uses a chimpanzee adenovirus viral vector that can’t cause disease in humans and expresses the SARS-CoV-2 spike protein genetic code into vaccinated people cells, which then produce the protein, teaching the immune system to recognise and attack the virus.
Out of 23,745 participants, 168 experienced a total of 175 severe adverse events over the period, but 172 events were unrelated to the COVID-19 or control vaccines, said Prof Pollard. Those are events that investigators considered medically significant and ranged from a broken leg to a heart attack, he said.
One event was in the control group (a case of haemolytic anaemia), one event was in the COVID-19 vaccine group; (a case of transverse myelitis considered possibly related to the vaccine), and a case of severe fever; was reported in South Africa in a participant who recovered rapidly without an alternative diagnosis and was not hospitalised. All three participants have; recovered or are recovering, and continue to be part of the trial, study authors have said in The Lancet.
Data was analysed from 23,745 adults in the UK, Brazil, and South Africa. The interim analysis pools the data, providing greater precision for efficacy; and safety outcomes than possibly in individual trials, and giving a broader understanding of the use of the vaccine; in different populations, said Prof Pollard.
The primary outcome of the study was to determine how many cases; of symptomatic COVID-19 disease were in participants who had received; two doses of the vaccine, compared with controls. Only cases that occurred 14 days after the second vaccination had been given were included.
There were 131 cases of symptomatic COVID-19 disease more than 14 days after; the second vaccine dose in these 11,636 people. This included 0.5 per cent cases; in the vaccine group and 1.7 per cent cases in the control group, which equates to a vaccine efficacy; of 70 per cent. Cases of severe disease and hospitalisation were monitored for in all 23,745 participants. From 21 days after the first dose, there were 10 cases hospitalised for COVID-19, all in the control arm, and two were; classified as severe, including one death. These are also secondary outcomes and; will require additional confirmation, said study co-author Prof Sarah Gilbert from the University of Oxford.