- Understanding immunity to SARS-CoV-2 infection is essential to understanding how it contributes to protection against reinfection
- Earlier studies indicated that immunity is short-lived, but the latest studies suggest otherwise
- One of these studies shows that immunity might last years, possibly decades
Scientists have been scurrying to understand immunity against reinfection with SARS-CoV-2 (the virus that can lead to Covid-19).
It is still not entirely clear how long contracting the virus confers immunity, with early studies suggesting a period of a few months, which, therefore, means that it may only provide temporary protection against reinfection.
One of these studies, for instance, found that antibody levels "waned quite rapidly" after infection in the British population, suggesting a risk of multiple infections, Health24 reported.
However, newer studies indicate immunity could last longer.
Some protection against reinfection
According to a study published in the renowned journal Nature Medicine, people who have recovered from Covid-19 have powerful and protective killer immune cells, even when antibodies are not detectable.
This, the authors wrote, “represents major determinants of immune protection on an individual as well as population level”.
In this study, a research team at the Medical Center – University of Freiburg in Germany found that after recovery from SARS-CoV-2 infection, immune cells are formed which remain in the body and could mediate a rapid immune response in case of reinfection.
"These so-called memory T-cells after SARS-CoV-2 infection look similar to those after a real flu,” said study co-author Dr Maike Hofmann, a scientist at the Department of Medicine II at the Medical Center – University of Freiburg.
“We are therefore confident that the majority of people who have survived SARS-CoV-2 infection have some protection against reinfection with SARS-CoV-2,” he added.
Study co-author, Dr Christoph Neumann-Haefelin, Head of the Gerok Liver Center at University Hospital Freiburg, also expressed optimism about their results, suggesting that immunity against the new coronavirus can be achieved after an infection, and that, “similarly, vaccines currently being tested in trials could provide significant protection against SARS-CoV-2".
What another recent study shows
Another, perhaps more hopeful, study shows that immunity might last years, possibly even decades.
In this study, the team of researchers at the La Jolla Institute of Immunology in California, and the Icahn School of Medicine at Mount Sinai in New York, investigated multiple compartments of circulating immune memory to SARS-CoV-2 in 185 Covid-19 cases, including 41 cases more than six months post-infection.
They found that eight months after infection, most people who recovered still had enough immune cells to fight off the virus and prevent illness.
In other words, there was a very slow rate of decline of these cells, demonstrating that they persist in the body for a very long time.
Although the research, published online in pre-print server bioRxiv, has not been peer-reviewed nor published in a scientific journal, the New York Times refers to it as “the most comprehensive and long-ranging study of immune memory to the coronavirus to date”.
“That amount of memory would likely prevent the vast majority of people from getting hospitalised disease, severe disease, for many years,” said Shane Crotty, a virologist at the La Jolla Institute of Immunology, with Dr Deepta Bhattacharya, an immunologist at the University of Arizona, believing that it’s not an unreasonable prediction to think that these immune memory components would last for years.
The Times also points to another recent study that showed that survivors of SARS, also caused by a coronavirus, still carry important immune cells 17 years after being infected. The results of this study have led scientists to be hopeful that studying antibodies may be largely beneficial in an effort to develop drugs to prevent or treat Covid-19.
While scientists continue in the global race to develop a Covid-19 vaccine to help bring the pandemic under control, these findings that immunity to the virus might not be so short-lived after all are likely to come as a relief to experts.