The levels of ACE2 blocking antibodies, three months after the COVID vaccination, were highest for Moderna, with Sputnik V and AZD1222 achieving equal levels, followed by those who received the first dose of Gam-COVID-Vac (Sputnik light) and then Sinopharm, Dr. Chandima Jeewandara of the Allergy, Immunology and Cell Biology Unit, Department of Immunology Molecular and Molecular Medicine of the University of Sri Jayewardenepura, said yesterday.

This follows a study conducted to compare the immunogenicity of different vaccines at the same time point post-vaccination, he said. The differences in the persistence of immunity to different vaccines were likely to have significant implications in breakthrough infection rates, hospitalization and severe disease in different vaccine recipients, he said.

“How could we use this data to benefit Sri Lankans factors to consider? 1. The majority of our population is vaccinated with Sinopharm. 2. We have already witnessed signs that vaccines lose their potency over time (waning of Immunity) 2. Variants 3. Availability of boosters,.”

Dr. Jeewandara said that WHO made a number of recommendations (on 16 December 2021) for countries considering heterologous schedules (mix and match), to ensure an equivalent or favourable immunogenicity of vaccine effectiveness:

“Countries implementing WHO EUL inactivated vaccines (e. g. Sinopharm) for initial doses may consider using WHO EUL vectored (AZ) or mRNA vaccines (Pfizer) for subsequent doses. Vaccines will continue to prevent severe disease caused by the variants — but to what extent is not yet clear. We are already witnessing that infections have been uncoupled from deaths in Sri Lanka,” he said.

Dr. Jeewandara said that if a person was vaccinated with Sinopharm, he or she should get a booster three months after completing the vaccination. “If you have recovered from COVID 19 after full vaccination (hybrid Immunity): you may delay the booster shot for six months, but it is best that you seek an opinion from your physician (severity of your illness, age, comorbidities and your medicines will affect the immunogenicity),” he said.