10 Percent of Wuhan Study Patients Lose Coronavirus Antibodies Within Weeks

Chinese scientists have cast doubt over whether we have long-lasting immunity to the coronavirus in two studies released this week, prompting them to question the use of immunity certificates.

The authors of the first study submitted to the pre-print website medRxiv concluded that people are unlikely to have protective antibodies against the coronavirus for long periods of time. As the findings are a pre-print, they have not been through the rigorous peer review process required to publish in scientific journals. Scientists partly release papers this way to prompt debate on a topic.

For the study, the scientists looked for antibodies specific to the coronavirus in the blood samples of 1,470 COVID-19 patients in three hospitals in Wuhan, China—the original epicentre of the pandemic. Previous research cited by the authors suggests that antibodies which make up the first line of defense against the coronavirus are detectable around 7 days after a person is infected, while virus-specific antibodies can take around two weeks.

Dr. Xinghuan Wang of the urology department at Zhongnan Hospital of Wuhan University and colleagues also assessed the blood of 3,832 healthcare providers who didn't test positive for the coronavirus from one of the three hospitals, as well as 19,555 members of Wuhan's general population, and 1,616 non-COVID hospital patients. The participants had coronavirus and antibody tests between February 29 to April 29. On average, COVID-19 patients were tested for antibodies 41 days after they first showed symptoms.

As the coronavirus emerged in Wuhan, the authors worked on the assumption that most healthcare workers who took part in the study were "inevitably" exposed to the bug in the early days of the outbreak, in late November 2019 to January 20, 2020, when it was spreading unchecked and they weren't wearing sufficient protective equipment.

The team found that 89 percent of hospitalized COVID-19 patients had virus-specific antibodies against the coronavirus, compared with 4 percent of healthcare workers and the general population, and 1 percent of non-COVID patients.

The authors believe the healthcare workers were infected with the coronavirus but produced no long-lasting antibodies against the germ.

They backed up their argument by pointing to antibody test studies in countries including the U.S. that suggest between 10 to 80 times more people may have been infected by the coronavirus than are reflected in diagnostic test results. For instance, one study on people in Wuhan found around 10 percent of the tested population had antibodies to the coronavirus, around 20 times higher than the number of confirmed cases in the city.

According to the scientists, the around 10 percent of COVID-19 patients in their pre-print study who didn't have antibodies 21 days after their symptoms started likely "lost" them after they recovered.

In contrast, patients with severe acute respiratory syndrome (SARS) have been known to carry antibodies for up to 210 days, the researcher said.

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A blood sample for a coronavirus antibody test is shown on June 16, 2020 in Washington, DC. Win McNamee/Getty Images

The study was limited, the team said, because they did not have long-term data on the recovered COVID-19 patients and whether they retained their antibodies. In addition, antibody tests are not necessarily entirely reliable.

They said: "Very few healthcare providers had IgG [virus-specific] antibodies to SARS-CoV-2 [the COVID-19 coronavirus], though a significant proportion of them had been infected with the virus.

"After SARS-CoV-2 infection, people are unlikely to produce long-lasting protective antibodies against this virus."

Daniel M. Davis, professor of immunology at the University of Manchester, who did not work on the paper, told Newsweek interpreting the findings is difficult as much of the team's data comes from a time when the use of personal protective equipment was sparse in these hospitals.

"So the researchers interpret their results to mean that, because these healthcare workers were very likely exposed to the virus, antibodies may not be produced to a detectable extent in all people infected. This is arguable because this assumes that transmission rates of the virus was high in this hospital at that time, something which can't easily be tested."

Davis, the author of The Beautiful Cure, a book about the immune system, said: "Overall, these results are interesting and provocative but more research is needed, following large numbers of people over time. Only then, will we clearly know how many people produce antibodies when infected with coronavirus, and for how long."

Asked whether he agrees with the authors' conclusion, Professor Sanjeev Krishna of the Institute for Infection and Immunity at St. George's University of London, who also didn't work on the paper, told Newsweek: "The features that contribute to immunity from SARS-CoV-2 [coronavirus] infections are still in the process of being worked out, so it is probably too early to conclude anything too strongly.

"We have observed, for example, that the stronger the inflammatory reaction to the infection, the higher the antibody levels produced. Of course, this is also associated with more severe disease. Other factors such as the ethnic background, genetic factors and how much virus causes the infections may also be important."

In a separate peer-reviewed piece of research published in the journal Nature Medicine, scientists found asymptomatic patients appeared to have weaker immune responses than COVID-19 patients who showed symptoms.

The study involved 178 COVID-19 patients who were hospitalized even if they didn't have symptoms according to government policy. Of the total, 37 were classed as asymptomatic as they didn't have any symptoms in the past 14 days or while they were in hospital. The remaining 141 were mild cases.

Symptomatic patients had significantly higher levels of virus-specific antibodies than the asymptomatic during the period when the virus could still be detected in their respiratory tracts.

Eight weeks after the patients were discharged from hospital, 81 percent of asymptomatic patients saw levels of their neutralizing antibodies drop compared with 62 percent of symptomatic patients.

"In this study, we observed that IgG [virus-specific] levels and neutralizing antibodies in a high proportion of individuals who recovered from SARS-CoV-2 infection start to decrease within 2–3 months after infection," co-author Ai-Long Huang, of the Key Laboratory of Molecular Biology on Infectious Diseases at China's Chongqing Medical University, and colleagues wrote in the paper.

Based on their respective research, both teams questioned the idea of immunity certificates. The Nature Medicine team said their work and that of others "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.

Echoing their concerns, the medRxiv researchers said: "As infected people do not develop long-lasting protecting antibodies against SARS-CoV-2, the idea of immune certificate for recovered COVID-19 patients is invalid."

This article has been updated with comment from Sanjeev Krishna.