AstraZeneca is working with regulators to investigate a lower dose Covid-19 vaccine that performed better than a full dose, a company spokesman said.
The vaccine developed by Oxford University was 90 percent effective in preventing Covid-19 when it was administered as a half dose, followed by a full dose at least one month later, according to data from late-stage trials in Britain and Brazil.
Another dosing regimen showed 62 percent efficacy when given as two full doses at least one month apart, and the combined analysis from both dosing regimens resulted in an average efficacy of 70 percent.
No serious safety events related to the vaccine have been confirmed and it was well tolerated across both dosing regimens, the company said.
"There is strong merit in continuing to further investigate the half-dose/full dose regimen," said an AstraZeneca spokesperson.
"We are further evaluating the data and will work with regulators on the best approach for further evaluation. This would add to data from existing trials which are currently being prepared for regulatory submission."
AstraZeneca chief executive Pascal Soriot said the company was likely to run an additional global trial to assess the efficacy of its Covid-19 vaccine, according to Bloomberg News.
Instead of adding the trial arm to an ongoing US process, a new trial would be run to evaluate the lower dosage, Bloomberg News said.
AstraZeneca is facing tricky questions about its success rate that some experts say could hinder its chances of getting speedy US and EU regulatory approval.
Several scientists have raised doubts about the robustness of results showing the shot was 90 percent effective in a sub-group of trial participants who, by error initially, received a half dose followed by a full dose.
When asked about the doubts raised about the vaccine, the British government's chief scientific adviser, Patrick Vallance, said the main point was that it worked.
"The headline result is the vaccine works and that's very exciting," Vallance said, during a news conference with UK Prime Minister Boris Johnson.
The UK government's chief medical adviser, Chris Whitty, said there was always scientific debate.
"The key thing from our point of view is to leave this in the hands of the regulator... They will make an assessment with lots of data that is not currently in the public domain on efficacy and on safety," Whitty said.
Developers of the Sputnik V Covid-19 vaccine said AstraZeneca should try combining its experimental shot with the Russian one to boost efficacy.
Russia said its Sputnik V vaccine was 92 percent effective at protecting people from Covid-19, according to interim trial results, while AstraZeneca said its vaccine was 70 percent effective in pivotal trials and could be up to 90 percent effective.
"If they go for a new clinical trial, we suggest trying a regimen of combining the AZ shot with the #SputnikV human adenoviral vector shot to boost efficacy," the developers of the Russian vaccine said on their Twitter account.
"Combining vaccines may prove important for revaccinations."
With 2,187,990 infections, Russia has the fourth-largest number of Covid-19 cases in the world, behind the United States, India and Brazil.
AstraZeneca said it would have as many as 200 million doses of its vaccine by the end of 2020.
The British developed vaccine is viewed as offering one of the best hopes for many developing countries, because of its cheaper price and ability to be transported at normal fridge temperatures.
- Reuters/ RNZ