Covishield single-dose efficacy drops after 16 weeks in those above 60 years of age: Sri Lankan research

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The efficacy of the single dose of Oxford-AstraZeneca COVID-19 vaccine Covishield dropped at 16 weeks for those above the age of 60, while 93 per cent of the younger population showed very good responses during the same duration, university research in Colombo has shown. The vaccine is produced by the University of Oxford and British-Swedish multinational pharmaceutical and biotechnology company AstraZeneca.

Serum Institute of India (SII), the world's largest vaccine manufacturer, has entered into a collaboration with the University of Oxford and AstraZeneca to manufacture Covishield.

"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 of the Department of Immunology and Molecular Sciences of the Sri Jayawardenepura University has said in a tweet.

"Our paper on the first dose responses of Covishield vaccine is published in @NatureComms. 93.4% of 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.

Sri Lanka is still waiting to vaccinate over 500,000 people with the second jab of Covishield. They were the first recipients of the vaccine in its initial roll out of the country's vaccination campaign which began in late January.

The island kicked off its vaccination drive with the receipt of India's gift of 500,000 doses of Covishield. However, India's surge in COVID-19 cases since March and the suspension of the vaccine's export to other countries has upset Sri Lanka's subsequent orders with the Serum Institute.

The government has placed an order for 10 million doses of AstraZeneca vaccine from the Serum Institute of India at a cost of USD 52.5 million and a further 3.5 million doses directly from AstraZeneca Institute of UK under the COVAX programme.

Meanwhile, the anticipated stocks of Covishield from Japan under the COVAX facility are being further delayed, health officials said.

The island has so far vaccinated 8.7 million with the first dose, while 1.9 million had received the second dose, according to the ministry of health.

These vaccinations have mostly been done from the Chinese sinopharm COVID-19 vaccine. Sri Lanka has already procured 12 million doses of the vaccine.

China would make available 4 million more doses in the first week of August, the Chinese embassy has announced. According to Johns Hopkins University coronavirus data, Sri Lanka has reported 301,832 COVID-19 cases and 4,258 deaths.

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