A local study revealed that the antibody response decline in all age groups, 12 weeks after being fully vaccinated with the Sinopharm vaccine, especially among those over the age of 60. However, the study finds that the T cell response persists. 

It had been conducted by a group of virologists from Sri Lanka and the University of Oxford to determine the kinetics and persistence of immune responses following the Sinopharm/BBIBP-CorV, by investigating the immune responses in a cohort of Sri Lankan individuals.

The Sinopharm is an inactivated COVID-19 vaccine, which is currently given emergency use authorization by the WHO and is the main vaccine used in many Asian and Middle East Countries.

“Antibody responses declined in all age groups, especially in those who are more than 60 years after 12 weeks from the second dose, while T cell responses persisted.” Said Prof. Neelika Malavige, Head, Department of Immunology and Molecular Medicine of University of Sri Jayewardenepura. 

USJ researchers including Prof. Neelika Malavige and Dr. Chandima Jeewandara from Allergy Immunology and Cell Biology Unit, Department of Immunology and Molecular Medicine of University of Sri Jayewardenepura have been studying immune responses to different types of COVID-19 vaccines used in Sri Lanka.

Results of the current research show that while the SARS-CoV-2 specific total antibodies, and especially neutralizing antibodies and antibodies to the receptor binding domain significantly declined, the memory T cell and B cell responses persisted.

“Since the ACE2 receptor blocking antibodies (neutralizing antibodies that associate with protection) was shown to significantly decline in all age groups and especially in  the  elderly, it  is  important  to  carry out long term efficacy studies to assess the waning of immunity on hospitalization and severe disease in order to decide on booster doses in different populations.” said Prof. Malavige.