Researchers tested 739 asymptomatic staff at Cardiff Metropolitan University in July 2020 during the first wave of the pandemic and again three months later.
Antibody production forms the foundation of immunity, and yet it remains unclear what quantity of coronavirus antibodies are produced across the population, how long they last and whether they provide adequate protection against reinfection, frustrating public policy initiatives and medical research alike.
Some 3.65% of the participants were found to have Covid-19 antibodies, slightly below the national average of between 4% and 6% at that time, and all participants reported feeling well and hadn't been diagnosed with Covid-19. Participants reported only sporadic instances of some of the milder symptoms at various points in the previous three months.
The researchers found no statistically significant difference between male or female participants who had antibodies at the initial point in the study, though men over the age of 40 did tend to have higher antibody prevalence than any other demographic.
Among those who tested positive for Covid-19, however, coronavirus antibody levels were three times higher in men than women, despite no difference in symptoms reported, implying no difference in severity of past infection.
In the follow-up study three months later, among those previously found to have coronavirus antibodies, 21.7% no longer tested positive, suggesting that coronavirus antibodies are lost after six months.
Some 80% of those who lost their antibodies entirely were women and tended to be, on average, ten years older than the women who managed to retain their antibody protection, suggesting some altered immune response related to the menopause.
Immunity to Covid-19 appears to vary across the sexes and depends on the age of a person, which suggests a challenging road ahead for re-opening the wider world once vaccinations have been distributed more thoroughly.