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A preprint, an unpublished non-peer reviewed study, from the Oxford Vaccine Group looks at correlates of protection against SARS-CoV-2 infection.
Dr Peter English, Retired Consultant in Communicable Disease Control, Former Editor of Vaccines in Practice, Immediate past Chair of the BMA Public Health Medicine Committee, said:
“One of the most important aspects of the adaptive immune system – and the one we know most about (because it’s relatively easy to measure) – is the antibody response. It’s far from being the be-all and end-all of immunity – cellular responses are also very important. But this study aims to measure the antibody levels which are associated with protection against symptomatic Covid-19 infection – the “correlates of protection”.
“When we encounter a pathogen like the SARS-CoV-2 virus which causes Covid-19, and we are already immune (through vaccination or prior infection), antibodies can disable or neutralise it, preventing it from (in the case of SARS-CoV-2) latching on to the receptors that enable it to enter and infect cells. Antibodies can also enable other cells in the immune system to come and destroy the virus.
“(Once the virus is inside our cells, other parts of the immune system, including cellular immunity, come into play, destroying infected cells.)
“There are various ways in which knowing about the “correlates of protection” are valuable. They include: predicting duration of immunity post-vaccination; deciding when to give additional booster doses of vaccine; and predicting the likely value of candidate vaccines.
“They help us predict how long immunity will last if we know what levels of antibodies are required from protection (the “correlates of protection”), the level of antibodies following vaccination, and the approximate rate at which antibody levels decline. (This may give pessimistic responses, because if there is immune memory, antibody levels can very rapidly return to high levels following subsequent exposure.)
“They help planning subsequent booster intervals (after the initial booster dose in a prime-boost vaccination regime). By observing how quickly people’s antibody levels decline, we can get an idea of when they might, again, be susceptible to infection (although again, if they have immune memory, they might have better protection than such models might predict).
“And they help scientists developing new or different vaccines against SARS-CoV-2 by providing better understanding of what antibody levels their vaccines will need to induce if they are to provide protection from symptomatic infection.”
Prof Jonathan Ball, Professor of Molecular Virology, University of Nottingham, said:
“This study provides important insights into the levels of antibodies that are associated with protection from COVID19 symptoms. In future this kind of information might prove useful to identify individuals who have insufficient immunity to protect them from symptomatic infection following vaccination.
“Whilst very useful, the data doesn’t tell us anything about the possible contribution of T cells to protection, and because the immune analysis was performed on a single blood sample obtained 4 weeks after the vaccine boost, it doesn’t tell us how rapidly protection might wane in different groups of people.
“As the authors point out, one of the other key unknowns will be the impact of virus variants on immune protection.”
Preprint (not a paper): ‘Correlates of Protection against symptomatic and asymptomatic SARS-CoV-2 infection’ by Shuo Feng et al. was posted online on Thursday 24 June 2021. This work is not peer-reviewed.
https://www.medrxiv.org/content/10.1101/2021.06.21.21258528v1
All our previous output on this subject can be seen at this weblink:
www.sciencemediacentre.org/tag/covid-19
Declared interests
Dr Peter English: “No conflicts of interest to declare.”
Prof Jonathan Ball: “Receiving funding to develop DNA-based COVD19 vaccines.”