The vaccine being developed by US biotech company Novavax has shown high levels of effectiveness against Covid-19, according to data from UK and South African trials.
Results show an overall 100% protection against hospitalisation and death across all trials and high levels of efficacy against original and Kent strains in the UK, the firm reported.
But experts sounded a note of caution as much lower rates of efficacy were found against the South African strain underpinning the risk that variants may pose to vaccine campaigns and the potential need for booster doses.
The UK has secured 60 million doses of the vaccine, which is due to be manufactured in Stockton-on-Tees. Novavax said it would expect the data to be the basis for its application for regulatory approval to various agencies worldwide.
The vaccine uses a different technology to both the Pfizer/BioNTech and Oxford/AstraZeneca vaccines, combining an engineered protein from the virus that causes Covid with a plant-based ingredient to generate an immune response.
It confirms interim data from a UK study of 15,000 participants, the vaccine was 96.4% effective against the original strain and 86.3% effective against the Kent variant which is now the dominant strain in the country.
There were five cases of severe Covid-19 reported in the trial and all were in the placebo group. In those 65 years and older, 10 cases of Covid-19 were observed, 90% of which were in the placebo group, the firm reported.
But results from South Africa, where the B.1.315 variant predominates, showed an efficacy of 48.6% or 55.4% in a separate study of HIV-negative participants.
Professor Paul Heath, the chief investigator of the UK Novavax trial, said:
‘These are enormously exciting findings and confirm the results of the earlier interim analysis.
‘This is a highly effective and safe Covid-19 vaccine and one that is effective against the important UK variant. This wonderful news is a tribute to the over 15,000 volunteers in our trial, to the dedication of the UK investigators and to the huge support of the NIHR.’
Dr Michael Head, senior research fellow in global health at the University of Southampton, said the data from Novavax continued the stream of excellent news about vaccines and pointed out that the company had announced it would be contributing over 1 billion doses to the COVAX initiative.
‘One note of caution is the observed lower effectiveness against B.1.351 variant of concern, as first observed in South Africa.
‘This shows the impact variants can have upon the pandemic response and thus is a strong argument for keeping cases as low as possible whilst the burden of Covid-19 is high.’
Medicines regulators in the UK say Covid vaccines which have been modified to better tackle variants of the virus will be fast-tracked for approval just like flu vaccines.