One study has already been peer-reviewed and published, while the other still has to be reviewed but the findings suggest the same outcome.
The first study, published in Nature Medicine, found that people who had acquired the virus carried antibodies thereafter — but only for about two to three months.
Conducted in China’s Wanzhou District, the study focused on 37 symptomatic and 37 asymptomatic people who had tested positive for the virus.
It was found that the latter had a weak antibody response compared with those who did have symptoms when infected.
Two months later, of those who were asymptomatic, 40% had undetectable levels of antibodies.
Of the symptomatic patients, only about 13% still had antibodies in their systems.
Molecular biologist and co-researcher Ai-Long Huang, of Chongqing Medical University, said that their findings “indicate the risks of using Covid-19 ‘immunity passports’ and support the prolongation of public health interventions, including social distancing, hygiene, isolation of high-risk groups and widespread testing”.
The second paper, published as a “preprint” in medRxiv (a journal for studies still requiring peer review), was based on research done in Wuhan where Covid-19 first emerged as a zoonotic disease, from bats to humans.
This study, led by Wuhan University, also concluded that people are unlikely to have any form of long-term immunity from Covid-19.
Lead author Xinghuan Wang and the team looked at the blood samples of 1,470 Covid-19 patients in three different hospitals in the city.
According to mathematical modelling, it was estimated that 25% of the about 23,000 participants had contracted the virus, and yet only 4% had any antibodies a few weeks after recovery.
“After SARS-CoV-2 infection, people are unlikely to produce long-lasting protective antibodies against this virus,” concluded Wang and the team, while also acknowledging that more long-term data would be needed to augment their findings.
Wang said the findings “have important implications for herd immunity, antibody-based therapeutics, public health strategies, and vaccine development”.
By TANYA FARBER