Nature reports:

Six months ago, Miles Davenport and his colleagues made a bold prediction. On the basis of published results from vaccine trials and other data sources, they estimated that people immunized against COVID-19 would lose approximately half of their defensive antibodies every 108 days or so. As a result, vaccines that initially offered, say, 90% protection against mild cases of disease might only be 70% effective after 6 or 7 months.

“It felt a little bit out on a limb at the time,” says Davenport, a computational immunologist at the University of New South Wales in Sydney, Australia. But on the whole, his group’s predictions have come true.

Immunological studies have documented a steady decline of antibody levels among vaccinated individuals. Long-term follow-up of vaccine trial participants has revealed a growing risk of breakthrough infection. And health-care records from countries such as Israel, the United Kingdom and elsewhere all show that COVID-19 vaccines are losing their strength, at least when it comes to keeping a lid on transmissible disease.

That’s without accounting for the Delta threat either — and it’s clear that vaccine–induced antibodies do a worse job at recognizing SARS-CoV-2 variants compared with the ancestral strain of the virus. What remains unclear, however, is to what degree the immune system’s safeguards that protect vaccinated people against severe disease, hospitalization and death might be fading as well. “That,” says Davenport, “is the million-dollar question at the moment.” [Continue reading…]