A study, published in PLOS Pathogens, looked at antibody responses and duration in COVID-19 patients.
Professor Danny Altmann, Professor of Immunology at Imperial College London and British Society for Immunology spokesperson, said:
“After the initial publications about SARS-CoV-2 antibody assays and levels, important papers are starting to emerge which look at specificity and durability of the response in more detail. Studies like this are a vital part of the ‘work-in-progress’ to make sense of who has immunity and how long for. This paper makes a number of points: the gold-standard in assessing the antibody response to a virus is measuring ability to neutralise the entry of virus into cells, although this is not one of the routinely available tests. Most convalescent patients show this response though, importantly, 20% do not. Also, this antibody level declines in most people by the time of their follow-up appointment a month later. Once again, evidence shows that the half-life of these antibodies in the blood is not particularly sustained. We don’t know to what extent this is bad news unless we know the extent to which the white blood cells that make the antibody (B cells) are up and ready to defend against any repeat attack.”
Dr Alexander Edwards, Associate Professor in Biomedical Technology, Reading School of Pharmacy, University of Reading, said:
“I don’t see that it’s a ‘game changer’- it certainly adds more data to existing studies, but nothing dramatically new pops out. All these studies are vital right now as we seek to fill in details and build up a detailed understanding of our immune response to SARS-CoV-2 virus in COVID-19 patients. The study illustrates that there are multiple antibody measures and that these will change over time. We wouldn’t expect antibody levels to remain high all the time, but the antibody ‘memory’ would mean that although levels might be low, there may be some level of protection. This paper doesn’t really answer that question.
“This also should be a reminder that antibody testing is far from perfect – different tests measure individual parameters, but people won’t necessarily have the same levels of antibodies that know how to target and defeat different proteins such as the spike in the coronavirus. Individual tests still can’t tell us for certain how immune a person is against Covid-19, and only with longer, larger studies will we be able to answer the big questions like how antibody levels affect severity and reinfection.
“It’s hard at the moment to get a consensus view of big questions such as ‘how long does immunity last’ or ‘how long do antibody responses last’. Even the technical details can vary a lot leading to slightly different patterns of antibody observed in different studies. Some of the measurements made in this study rely on a single dilution of patient sample (i.e. measuring an “OD value” estimate of antibody level), rather than testing multiple dilutions to fully quantify antibody levels (i.e. measuring antibody titre).
“The study is not able to or designed to correlate any particular antibody measurement with protection from re-infection or with disease severity. It’s also vital to remember that antibody levels do fluctuate over time, naturally, as our bodies adapt to infection or recovery. For example, when you are ill with an infection or inflammatory disease, you will have higher levels of most immune components – not just higher levels of antibody. When you recover, these levels will drop back down again. So you’d expect anti-viral antibody levels to peak whilst virus is present, and fall back afterwards- this does not mean you aren’t protected from re-infection.
“This study has quantified antibody against a wide range of different virus components which is important because many early studies focus on just one target. For example, the serosurveillance tests used in the UK for the ONS monitoring studies will measure antibody against one target- for example S or N protein. This approach is correct as it’s very important for consistency to use the same test for studies over time or populations, but some individuals may generate slightly different immune response profiles, that may not give positive response in one particular antibody test. Individual antibody tests still don’t confirm for certain how immune that person is.
“The remaining unanswered question is still: how do these fluctuations in antibody levels affect both COVID-19 severity, and the chances of catching the same infection a second time.”
‘A comprehensive, longitudinal analysis of humoral responses specific to four recombinant antigens of SARS-CoV-2 in severe and non-severe COVID-19 patients.’ by Chen el al was published in PLOS Pathogens on Thursday 10th September at 19:00 UK time.
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Dr Alexander Edwards: No COIs.
None others received.