The efficacy of the single dose of Covishield dropped at 16 weeks for those above the age of 60, while 93 per cent of the younger population showed good responses during the same duration, a university research in Colombo has shown.

“Our preprint on waning immunity at 16 weeks after a single dose, in the elderly individuals. Neutralising antibodies and antibodies for variants wane in the elderly but memory responses intact. However, even after a single dose, those younger than 60 had very good responses. 93 per cent had antibodies at 16 weeks, after a single dose,” Professor Neelika Malavige, Department of Immunology and Molecular Sciences, Sri Jayawardenepura University said in a tweet.

“Our paper on the first dose responses of Covishield vaccine is published in @NatureComms. 93.4% individuals developed antibodies to a single dose of the vaccine and 97.1% developed neutralising antibodies.

“Funding for the study was by the @UKinSriLanka, @WHOSriLanka and Chinese Academy of Science,” she said.