Virus-fighting antibodies may linger in our bodies for as long as one-to-two years after we're infected with Covid-19 – something that bodes well for booster shots in a post-pandemic world.
Antibodies play a critical role in the immune system's fight against pathogens like the coronavirus.
Upon a new virus being recognised, antibodies are specially created to bind to its "spike protein" and stop it entering our cells - all while signalling other parts of the immune system to destroy the foreign invader.
A new study led by University of Canterbury mathematician Associate Professor Alex James - and published online ahead of peer review - modelled data taken from six papers to show that, in most patients, these antibodies are long-lasting.
The antibody response predicted by model had two stages - an initial peak after infection, and a relatively fast decline from this peak.
Then, the levels of antibodies essentially levelled off and the decline was much slower.
This levelling off in antibodies suggested the immune system was switching from the original response to the virus to a longer-term memory response.
When the datasets were analysed together, the model showed the initial peak lasted for about 17 days before the antibodies levelled off, and the "half-life" was 345 days.
This implied that, one to two years after infection, antibodies would be at approximately 23 per cent and 11 per cent of their maximum level respectively.
"This is a highly encouraging result and if vaccine immunity follows a similar pattern it gives hope that yearly or even two-yearly booster immunisations could be sufficient to provide long-lasting immunity," James and colleagues said.
Study co-author and University of Auckland immunologist Associate Professor Nikki Moreland added: "This is really good news, as it means most people are likely to develop immunological memory after a Covid-19 infection.
"This memory can then be activated and provide protection when someone is exposed to the virus again."
So far, she said, data on Covid-19 vaccines indicated the same pattern of antibody response was likely to develop after vaccination, including a good long-term memory response.
"We still need to wait a few more months before this can be modelled accurately to determine if or when booster shots might be needed."
One of the studies the modelling drew on included a group of 112 New Zealand patients previously infected with the virus, the bulk of whom suffered mild symptoms.
That not only found their antibodies were long-lasting, but that they did so in a virus-free environment where Covid-19 had been eliminated.