Waning vaccine protection

A study involving the MRC/CSO Social and Public Health Sciences Unit's Professor Vittal Katikireddi found that the protection offered by the Oxford-Astra Zeneca COVID-19 vaccine declines after three months of receiving two doses.

Photo of a bottle of covid vaccine and syringe

The findings – drawn from datasets in Scotland and Brazil – suggest that booster programmes are needed to help maintain protection from severe disease in those vaccinated with Oxford-Astra Zeneca.

Professor Katikireddi said:

"We studied two million people in Scotland and over 42 million people in Brazil who had received two doses of the Oxford-AstraZeneca vaccine. More than four months after receiving a second dose, the risk of experiencing either a Covid-19 hospitalisation or death was approximately five times greater than the period of maximum vaccine protection after accounting for changes in infection rates and a range of other factors."

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Srinivasa Vittal Katikireddi, Thiago Cerqueira-Silva, Eleftheria Vasileiou, Chris Robertson, Sarah Amele, Jiafeng Pan et al Two-dose ChAdOx1 nCoV-19 vaccine protection against COVID-19 hospital admissions and deaths over time: a retrospective, population-based cohort study in Scotland and Brazil The Lancet (2021)

First published: 28 June 2018

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