Long-lasting immunity is more likely than expected

Georgina Hayes

SCIENTISTS are growing increasingly confident about the human immune response to Covid-19 after studies showed antibodies provide real-world protection against the virus and cellular immunity may be long-lasting.

A study of an outbreak on a Seattle fishing boat involving more than 100 sailors has shown that antibodies can provide protection against reinfection, while encouraging evidence has been found that T and B cells remain in the blood even once antibodies fade.

“This is exactly what you would hope for,” Marion Pepper, an immunologist at the University of Washington and an author of one of the studies told The New York Times. “All the pieces are there to have a totally protective immune response.”

“This is very promising,” echoed Smita Iyer, an immunologist at the University of California, in Davis. “This calls for some optimism about herd immunity, and potentially a vaccine.”

Antibodies have long been thought to protect against reinfection but the first study to use real-world evidence was published last week by researchers at the University of Washington.

It tracked the 122-strong crew of a fishing boat operating off the coast of Seattle. All were tested for both antibodies and the virus before they sailed and after. An outbreak occurred on the vessel and 104 people became infected.

However, only those without preexisting antibodies caught the virus. Three crew members who had already been exposed to the disease did not show evidence of reinfection.

Prof Danny Altmann, of the department of immunology and inflammation at Hammersmith Hospital, Imperial College London, said: “While this is a small study, it offers a remarkable, real-life, human experiment at a time when we’ve been short of hardline, formal, proof that neutralising antibodies genuinely offer protection from reinfection. It’s good news.”

There is also mounting evidence that T cells and B cells provide longer-lasting protection. A study by the Karolinska University Hospital and University Hospital of Wales, and a separate one in Seattle, found that people who recovered from asymptomatic or mild cases may have long-term T-cell immunity.