According to the Department of Allergy, Immunology and Cell Biology at the Faculty of Medicine, University of Sri Jayewardenepura, tests have shown that a single dose of the vaccine against the Indian Delta severe coronavirus produces only 33 % immunity.

Dr Chandima Jeewandara, the head of the study, said that this could not be considered a significant level of protection and that this was the biggest problem with the Delta variety.

He added that it was unlikely that a single dose would provide protection. The tests further revealed that although the two doses of Pfizer provided 85% protection, the AstraZeneca vaccine provided only 58 %protection.

However, all vaccines used in Sri Lanka respond effectively to the other severe coronavirus strain of the B117 alpha, he said.