Covid-19: New government study aims to track infection and immunity in population
BMJ 2020; 369 doi: https://doi.org/10.1136/bmj.m1636 (Published 23 April 2020) Cite this as: BMJ 2020;369:m1636Read our latest coverage of the coronavirus outbreak
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Dear Sir,
Currently great stress is being placed as to whether an individual has been infected with Covid-19 or whether he or she has not been infected. This has led to a push for widespread testing. In turn these two approaches rely on either antigen testing (showing the presence of the virus in the respiratory tract) or alternatively an antibody test ( which confirms recent or past presence of the virus within the body).
However, neither of these two tests approaches will detect an individual who has been exposed to the virus and has managed to eliminate it completely, before the virus has managed to come into contact with the body's "internal" immune system. The presumptive mechanism is by means of the extensive and effective mechanism within the respiratory tract. These individuals will have neither antigen nor antibody and could be classified as "exposed but not infected". One presumption is that their respiratory tract defence mechanism has effectively eliminated Covid-19 in the past and are likely to do so in the future.
It is unclear how often this theoretical but effective protective process takes place. To determine whether it does requires intrusive investigations, involving continuous gastric aspiration, matched with some very smart viral immunology of the gastric aspirate.
If, however, "exposed but not infected" individuals make up a significant proportion of the community it may cause difficulties in estimating what proportion of a population is still vulnerable to the ongoing Covid-19 virus in a community.
Paradoxically, some of those with negative Covid-19 tests, may actually have very robust intrinsic defence mechanisms and may not be susceptible to future infection.
Competing interests: No competing interests
Cardiac link with Covid-19 : Population Virus Tests may aid Cardiac risk assessment.
Dear Editor
This study of population antigen and antibody test is important and necessary but to what extent it will provide the expected answers remains to be seen.
It is very likely that there will be considerable number of inconclusive test results and yet those people still might have had the virus exposure but remained asymptomatic and recovered spontaneously. Therefore they may not react to positive antigen test and neither have reached the threshold to show positive antibody test. Of course repeated testing over weeks and months may generate some definitive answers but that will make interpretation of results more complicated. As the previous rapid response writer has said, that some people could remain in the category of “”exposed but not infected”” with both the antigen and antibody tests negative. Despite all that a study of this kind was long awaited and necessary to get as much information as possible.
Covid-19 exposure already caused a significant adverse cardiac impact and was found to have a link with complex cardiac disease and was associated with cardiac mortality and morbidity shown in a recent study and alerted by the NICE guidance - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7165109/
Therefore cardiac risk identification in Covid-19 affected general population is deemed necessary to avoid long term cardiac complications. This population virus test study could provide valuable results and identify a target population who might benefit from appropriate timely cardiac screening and early cardiac risk assessment to prevent sudden serious cardiac events.
Competing interests: No competing interests