Should I get a COVID-19 vaccine if I’ve already had COVID-19?
Natural infection with the coronavirus that causes COVID-19 may not lead to long-lasting immunity, so it is important to get the vaccine as well.
8 April 2021 – by Linda Geddes
When we’re exposed to a pathogen, such as the SARS-CoV-2 virus that causes COVID-19, immune cells called B and T cells become activated and launch a response that ultimately helps to destroy the pathogen. B cells produce antibodies that can both stop viruses from infecting further cells and flag them for destruction by other immune cells. T cells destroy virus-infected cells directly as well as facilitating the production of antibodies. As part of this process, B and T cells also produce memory cells that linger in the body and are primed to recognise and respond to that same pathogen, should they ever encounter it again.
Reinfections have been documented, which means that having had COVID-19 is no guarantee against catching it again. This is why it is important to get vaccinated.
However, for reasons that aren’t fully understood, this “immune memory” is more effective against some pathogens than others. Coronaviruses seems to be quite good at evading it, which is why you can catch the same common cold virus more than twice. For SARS-CoV-2, we still don’t know how long immunity after natural exposure lasts, and this is likely to vary between different individuals. However, reinfections have been documented, which means that having had COVID-19 is no guarantee against catching it again. This is why it is important to get vaccinated.
We also don’t yet know how long the immune protection conferred by COVID-19 vaccines will last. But we do know that receiving a second dose of many of the approved vaccines results in higher levels of protection. There is also some evidence that a single dose of vaccine acts like a second “booster” dose in individuals who have already had COVID-19, resulting in a stronger immune response to the virus. So, even if you have already had COVID-19, getting fully vaccinated, as is recommended by most countries, will equip you with an added layer of protection.