Why bone marrow cells may mean coronavirus antibodies ‘last years’

Immunity against Covid-19 may last for years in people who have recovered from the virus or received a vaccine, two new studies suggest.

Cells found in bone marrow that are generated during an immune response “may retain a memory of the virus”, The Times reports, meaning they “can produce long-lasting antibodies as a defence against future infections”.

Research published this week in Nature and on BioRxiv, a pre-print online research site, both suggest “these cells strengthen over a period of at least a year”, suggesting people “may not need booster shots… for a considerable period of time”, the paper adds.

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The studies “looked at people who had been exposed to the coronavirus about a year earlier” and found “cells that retain a memory of the virus persist in the bone marrow and may churn out antibodies whenever needed”, The New York Times (NYT) says.

“These so-called memory B cells continue to mature and strengthen for at least 12 months” after infection or vaccination, the paper adds.

“It’s normal for antibody levels to go down after acute infection, but they don’t go down to zero; they plateau,” Ali Ellebedy, an assistant professor at Washington University in St Louis who led the Nature study, told The Times.

“These cells have been generated as part of the immune response and they live at this stage for a very long period and continue to secrete antibodies.

“These cells are not dividing. They are quiescent, just sitting in the bone marrow and secreting antibodies. They have been doing that ever since the infection resolved, and they will continue doing that indefinitely.”

Ellebedy’s study monitored antibody levels in 77 patients who tested positive for Covid-19, finding that antibody levels in their bone marrow fell after four months but were still present after 11 months.

The findings will serve to “soothe fears that immunity to the virus is transient”, the NYT says, “as is the case with coronaviruses that cause common colds”. However, the results “may not apply to protection derived from vaccines alone” as “immune memory is likely to be organised differently after immunisation” when compared with natural infection.

Nonetheless, the studies will “give cheer to those concerned that antibodies produced after infection are short lived”, The Times adds, with Ellebedy suggesting that people who recover from the virus and are vaccinated may be “super protected”.

The two studies come after a separate study that found “the Oxford/AstraZeneca Covid-19 vaccine works well as a third booster shot”, the Financial Times reports, strengthening suggestions that the cheap, easily transportable jab could be used to provide an immunity boost.

A third jab was found “to boost participants’ antibodies to the coronavirus’s spike protein in an upcoming study by Oxford university”, the paper adds, despite concerns that “repeated use of the adenovirus vector – an inactivated cold virus – could stop the immune system recognising the virus’s spike protein”.

The study “kills all these arguments that you can’t use adenoviruses more than once”, a person familiar with the findings told the FT, adding that the immune response to a third shot was “unbelievable” and strong enough to “blow through almost any variant”.