The World Health Organization (WHO) has backed the use of the Oxford/Astra Zeneca Covid-19 vaccine after a review of the evidence.
Interim recommendations from its special advisory group (WHO SAGE) has concluded that the vaccine was found to be 63% effective overall and also recommended its use in people over the age of 65 years.
It also advised that the UK approach of spacing out the two doses is more effective, recommending an interval of 8-12 weeks.
The vaccine should be used even when variants which may make it less effective are circulating, WHO has recommended.
Some preliminary analyses from a Phase 1/2a trial in South Africa seemed to show marked reduction in vaccine effectiveness against mild and moderate disease caused by the South African variant but this was based on a small sample size.
The numbers in the study did not allow a specific assessment of vaccine efficacy against severe Covid-19, the WHO SAGE report said.
‘Indirect evidence is compatible with protection against severe COVID-19; however, this remains to be demonstrated in ongoing clinical trials and post-implementation evaluations.
‘In view of this, WHO currently recommends the use of [the Oxford/Astra Zeneca] vaccine according to the Prioritization Roadmap even if variants are present in a country,’ the advisory committee concluded.
The recommendations follow some debate about whether the vaccine is effective in older people. Some European countries including France and Germany had advised against its use in the over 65s.
WHO SAGE said that because a relatively small number of participants aged 65 years or over were recruited into the clinical trials, there were few cases of Covid-19 in either the vaccine or the control group making the confidence intervals on estimates of efficacy very wide.
‘More precise efficacy estimates for this age group are expected soon, from both ongoing trials and vaccine effectiveness studies in countries that are using this vaccine.
‘Immune responses induced by the vaccine in older persons are well documented and similar to those in other age groups. This suggests it is likely that the vaccine will be found to be efficacious in older persons,’ the interim recommendations concluded.
Professor Andrew Pollard, chief investigator on the Oxford vaccine trial, said: ‘The new guidance from WHO is an important milestone in extending access to the Oxford-AZ vaccine to all corners of the world and providing further endorsement that after rigorous scrutiny by the WHO Strategic Advisory Group of Experts the vaccine can be used to help protect populations from the coronavirus pandemic.’
Professor Sarah Gilbert who is also a chief Investigator on the Oxford vaccine trial, added: ‘It is excellent news that the WHO has recommended use of the SARS CoV-2 vaccine first produced in Oxford.
‘This decision paves the way to more widespread use of the vaccine to protect people against Covid-19 and gain control of the pandemic.’
A recent study suggested that the Oxford/AstraZeneca vaccine provides ‘minimal protection’ against mild to moderate infection with the South African variant of the virus.
But another study has suggested that the vaccine is effective against the Kent mutation of coronavirus.
