Covid-19: Do you need a booster if you have had the virus?
A virologist has been answering questions about how our immune systems make antibodies to fight Covid-19.
A huge push to offer all UK adults a booster shot by the end of the year is under way to tackle the rapid spread of Omicron.
The effectiveness of two vaccination doses decreases over time and research has found they offer limited protection from the new variant.
Dr Chris Smith, from the University of Cambridge, has been responding to the concerns of BBC Look East viewers. He was asked whether there is a limit to the number of antibodies our immune systems can produce and whether people who have recovered from Covid-19 have natural immunity.