We are seeing more people getting COVID-19 a second, third or fourth time. Often it is months between infections, but some people can catch it again within a few weeks. The likelihood of this occurring depends on two factors: how your immune system responds to the infection; and what variants are spreading locally.

For most people, the infection generates an immune response that lasts three to 12 months. After that, some people are more likely to be infected again, unless immunity is boosted with vaccination. The reason that some people catch it again within a few weeks is down to local virus transmission.

During the pandemic, some communities have had two or more variants spreading (like Delta and Omicron), with immunity from one not protecting from the other. Some people were re-infected in less than 90 days, with one person catching it again after 23 days.

This is why COVID precautions are so important, even after being infected or vaccinated.

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Asked by: Bella Jacobs, Salisbury

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Jeremy Rossman is a Senior Lecturer in Virology and President of Research-Aid Networks, University of Kent. His research focuses on the process of infectious disease outbreaks, and he has contributed to studies published in journals including PLoS Pathogens, Bioinformatics and Cell.