What are the new findings?
"This real world evidence shows that Covid-19 Vaccine AstraZeneca provides a high level of protection against the Delta variant, which is now a critical area of concern given its rapid transmission", Mene Pangalos, the executive vice president of AstraZeneca's BioPharmaceuticals R&D, said in a statement.
With earlier variants, each individual infection resulted in three to five new cases, he added.
The US Centers for Disease Control and Prevention has reclassified the Delta strain of Covid-19 as a variant of concern, based on "mounting evidence" of it being more transmissible, the media reported.
The paper, that is not yet peer-reviewed concluded that both the vaccines offered a high level of protection against the Delta variant of coronavirus.
Researchers found that two doses of both the AstraZeneca and Pfizer vaccines were effective in reducing hospitalizations among people who had contracted the Delta strain, but the effectiveness of the shots was "diminished" when to compared to those with the Alpha variant.
After 28 days post-vaccination, he said there was "only really" a difference in protection "of about 18 per cent" for the AstraZeneca vaccine, "which is not great". Higher efficiency against case of hospitalisation with severe symptoms was supported by T-sell response to the vaccine thus providing high and durable protection.
Initially detected in India, the B1.617.2 strain known as the Delta variant has already been detected in several countries across the world, including the UK, US, Singapore and Australia.
The study, published on Monday, analyzed the medical records of 14,000 people who had become infected with the Delta variant between April 12 and June 4. About 19, 500 confirmed Covid-19 cases were analysed out of which 377 sought hospital admission. "We will study and learn more about this variant". The risk of hospitalisation is more or less double than then in Alpha variant, the study further asserted.