Coronavirus: Antibody response studied by scientists to see how long immunity lasts
Recovering from Covid-19 may not offer lasting protection against future infections for those with only mild cases, according to a report which suggests caution regarding so-called herd immunity as well as the durability of vaccines.
Correspondence in the New England Journal of Medicine describes research on antibodies taken from the blood of 34 patients who had recovered after suffering mainly from mild symptoms that did not require intensive care. Only two needed supplemental oxygen and were given anti-HIV medication, and neither were on a ventilator or receiving remdesivir from Gilead Sciences Inc.
The first analysis was performed on antibodies taken an average of 37 days after the onset of symptoms, a second after about 86 days, or less than three months. The researchers found that the antibody levels dropped rapidly, with a half-life of around 73 days between the two periods. The loss of antibodies occurred faster than with SARS, an earlier type of coronavirus infection.
The antibody response is being closely studied by scientists around the world for clues about the duration of immunity. While there is little evidence to suggest that re-infections occur widely, health experts have yet to define details. The latest findings raise concerns that protection against reinfection may not last long in people with mild symptoms, which is the majority of cases.
Further studies will be needed “to define a quantitative protection threshold and a rate of decline of antiviral antibodies beyond 90 days”, according to researchers led by F. Javier Ibarrondo, of the David Geffen School of Medicine at the University. from California to Los Angeles.
Although the protective role of antibodies against infection is not fully understood, they are generally considered a good representation of some protection against infection in general, according to the report.
A recent study from King’s College London showed that antibody levels can drop to a degree that makes them undetectable as early as three months after infection. However, the body also mounts other forms of immune responses, including from so-called T cells, which appear to play a role in protecting against reinfection with Covid-19.
In Sweden, the country’s highest health authority said on Tuesday that people who have had the virus are likely to be immune for at least six months after being infected, whether or not they have developed antibodies. In new guidelines, the Swedish Public Health Agency said it was now considered safe for those infected to come into contact with people from high-risk groups.
(With the exception of the title, this story was not edited by GalacticGaming staff and is published from a syndicated feed.)
