Immunity fades within months, UK study finds

Immunity to COVID-19 may be short-lived because antibodies that work to prevent reinfection appear to fade within months, a study by British researchers has revealed.

Analysis of blood samples from more than 90 people infected with the novel coronavirus in the United Kingdom showed that while around 60 percent developed a robust antibody response at the peak of the infection, three months later, just 17 percent retained similar levels of antibodies.

Antibody levels fell as much as 23-fold over the period, and were totally undetectable in some cases, according to the study published by a team at King's College London. The paper was released on the preprint server Medrxiv and is yet to be peer reviewed.

Authors of the study said the findings have "important implications" for the durability of vaccines, as well as levels of protection against reinfection provided by antibodies.

Seasonal reinfections

If the body's immune response to COVID-19 is in fact this transient, herd immunity would be difficult to achieve and the virus could cause seasonal reinfections among much of the population, as is the case with viruses that cause the common cold and types of flu.

The long-term efficacy of vaccines would also be impacted, as inoculations often work by eliciting an antibody response.

"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," Katie Doores, a senior lecturer at King's College London and lead author on the study, told UK newspaper The Guardian. "People may need boosting and one shot might not be sufficient."

The findings add to a growing number of COVID-19 studies that have queried long-term immunity against the virus.

These include results from several antibody studies conducted by Wuhan University and the University of Texas at hospitals in Wuhan, the Chinese city which suffered a major outbreak of novel coronavirus.

Results from these studies and others have led some researchers to posit that an effective vaccine would need to encourage a T cell response, as well as antibodies. T cell production is a distinct and complementary immune response to antibody formation, and several recent studies suggest that these "search and destroy" cells could play an important role in fighting novel coronavirus infection.