The protection offered by the Oxford-Astra Zeneca Covid-19 vaccine declines after three months of receiving two doses of the preventive, according to a study published in The Lancet journal.

The findings drawn from datasets in Brazil and Scotland suggest that booster programmes are needed to help maintain protection from severe disease in those vaccinated with AstraZeneca, known as Covishield in India. The researchers analysed data for two million people in Scotland and 42 million people in Brazil who had been vaccinated with the AstraZeneca vaccine. In Scotland, when compared with two weeks after receiving a second dose, there was approximately a fivefold increase in the chance of being hospitalised or dying from Covid-19 nearly five months after being double vaccinated, the researchers said.