The New York Times reports:

It’s a question that has haunted scientists since the pandemic began: Does everyone infected with the virus produce antibodies — and if so, how long do they last?

Not very long, suggests a new study published Thursday in Nature Medicine. Antibodies — protective proteins made in response to an infection — may last only two to three months, especially in people who never showed symptoms while they were infected.

The conclusion does not necessarily mean that these people can be infected a second time, several experts cautioned. Even low levels of powerful neutralizing antibodies may still be protective, as are the immune system’s T cells and B cells.

But the results offer a strong note of caution against the idea of “immunity certificates” for people who have recovered from the illness, the authors suggested.

Antibodies to other coronaviruses, including those that cause SARS and MERS, are thought to last about a year. Scientists had hoped that antibodies to the new virus might last at least as long.

Several studies have now shown that most people who are visibly ill with Covid-19 develop antibodies to the virus, although it has been unclear how long those antibodies last. The new study is the first to characterize the immune response in asymptomatic people.

The researchers compared 37 asymptomatic people to an equal number who had symptoms in the Wanzhou District of China. The investigators found that asymptomatic people mount a weaker response to the virus than those who develop symptoms. [Continue reading…]