"We have some data that your immune system"s response to natural infection, but also to vaccination, wanes over time," says Andrew Ustianowski, clinical lead for the UK"s National Institute for Health Research Covid Vaccine Research Programme. "We can see the antibody responses, and to a degree, the T cell responses dropping over time. So, one of the hopes for second generation vaccines is that they can give us protection for a longer period than these first vaccines."