Experts say the study should be a warning to those assuming they are immune because they've already had it.

Immunity to Covid-19 in recovered patients may only last a few months, and it could be caught again like a common cold, according to a new study.

Researchers at King's College London looked into the immune response of 90 patients and healthcare workers at Guy's and St Thomas' NHS Trust and found antibodies peaked three weeks after the onset of coronavirus symptoms and then declined.

Blood tests showed "potent" level of antibodies could be found in 60% of participants during the peak of their battle with Covid-19; however, only 17% sustained that same level three months later.

Antibodies decreased 23-fold in some cases, and were depleted entirely in others.

Lead author Dr Katie Doores told The Guardian: "People are producing a reasonable antibody response to the virus, but it's waning over a short period of time and depending on how high your peak is, that determines how long the antibodies are staying."

She added: "Infection tends to give you the best-case scenario for an antibody response, so if your infection is giving you antibody levels that wane in two to three months, the vaccine will potentially do the same thing. People may need boosting and one shot might not be sufficient."

Her comments suggest patients who had the most severe cases of Covid-19 had the highest antibody levels, and in turn those antibodies lasted the longest.

The study also raises questions about the concept of "herd immunity" from future outbreaks.

Experts said that although the study is yet to be peer-reviewed, it should be a warning to those assuming they are immune if they have been infected with the virus in the past.

Mala Maini, professor of viral immunology and consultant physician at University College London, said: "This study does reinforce the message that we can't assume someone who has had Covid-19 can't get it again just because they initially became antibody-positive.

"It also means a negative antibody test now can't exclude you having had Covid-19 a few months ago.

"And it suggests vaccines will need to be better at inducing high levels of longer-lasting antibodies than the natural infection, or that doses may need to be repeated to maintain immunity."