Covid-19: Past infection provides 83% protection for five months but may not stop transmission, study finds
BMJ 2021; 372 doi: https://doi.org/10.1136/bmj.n124 (Published 14 January 2021) Cite this as: BMJ 2021;372:n124Read our latest coverage of the coronavirus outbreak
All rapid responses
Rapid responses are electronic comments to the editor. They enable our users to debate issues raised in articles published on bmj.com. A rapid response is first posted online. If you need the URL (web address) of an individual response, simply click on the response headline and copy the URL from the browser window. A proportion of responses will, after editing, be published online and in the print journal as letters, which are indexed in PubMed. Rapid responses are not indexed in PubMed and they are not journal articles. The BMJ reserves the right to remove responses which are being wilfully misrepresented as published articles or when it is brought to our attention that a response spreads misinformation.
From March 2022, the word limit for rapid responses will be 600 words not including references and author details. We will no longer post responses that exceed this limit.
The word limit for letters selected from posted responses remains 300 words.
Dear Editor
Will viral spike protein produced by mRNA vaccines cause recipients to develop a positive PCR (antigen) test (as opposed to only a positive antibody test)? If so, how will vaccinees be differentiated from genuinely infected individuals? And how long could they remain 'positive', giving the impression of a continuing pandemic?
In addition, does the partnership between manufacturers and private testing laboratories, who can, "create standard processes and quality control", represent a conflict of interest, by setting PCR Cycle Thresholds at levels to determine vaccine "success" or, "need for more doses"? (1)
(1) Why bypass NHS labs for mass testing? Concerns over new super-labs. The Lowdown 27 April 2020.
Competing interests: No competing interests
Dear Editor
I am sceptical of the findings of this study which claims that having had covid-19 previously provides 83% immunity protection for 5 months.
Firstly the study was carried out among healthcare workers not the general public who may have certain underlying conditions such as Diabetes, COPD, cardiac issues. So the findings may not be directly representative of the population at large.
Secondly, there are now 33 well documented cases of people around the world having repeated covid-19 reinfection. These cases are listed on the Cov-19 reinfection tracker website with literature citations which is constantly being updated. There well be many more cases of cov-19 reinfection being under reported. The PCR test has a serious short coming. It cannot definitively prove someone is infectious with live Sars-cov-2 virus.. This can only be established by a differential viral culture. It is possible for someone to have a positive PCR test result but be free of live virus as the test detects residual RNA fragments from a previous infections weeks after recovery. A negative PCR test result does not necessarily mean someone is not infectious, they may be incubating the virus again this would need a viral culture taken at the same time to confirm the person is not infectious. Were the PCR test results reported in this study confirmed by taking simultaneous viral cultures to determine infectious status?
Thirdly, the mean interval between covid-19 reinfection among the recorded 33 cases is 87 days, which is just under 3 months, much less than the findings of this study, so having a previous covid-19 infection may only give barely 3 months immunity. This suggests that the Chief Medical Officer's advice on extending the interval between Pfizer vaccinations from 3 to 12 weeks to be unwise as someone could easily acquire an infection between vaccinations.
My concern over vaccines is the manufacturers cannot quantify how long immunity protection might last, nor can they confirm whether they prevent viral transmission, nor can they adequately predict long term unintended adverse effects. In a sense the vaccine roll out in the population is substituting for a massive cohort challenge study.
References:
Covid-19 Reinfection Tracker. BNO News
Competing interests: No competing interests
Re: Covid-19: Past infection provides 83% protection for five months but may not stop transmission, study finds
Dear Editor,
What is the definition of protection? We know that immune response (not necessarily viral damage) often causes headaches, myalgia, and fatigue, (even chills/fever). Even mRNA vaccines (which only involve the Spike protein and no other viral aspect) can stimulate the immune response and present these symptoms.
So, how are "symptomatic" cases defined? Symptoms that are unique to viral damage like sore throat, congestion, cough, etc? Or do we include a short period of symptoms that are solely immune response?
Also, do we count asymptomatic infections as protective or non-protective? And what Ct is used to define "infection"? How are high Ct that are borderline negative and essentially non-shedding categorized? Should Ct be "banded" into categories of "strongly shedding", "moderately shedding", "borderline positive / lightly shedding", "negative" based on Ct counts so these categories could be used to identify PCR "positive-ness"?
I would propose that a number like 83% is meaningless unless a clear definition of what the 83% represents is clearly specified. Below we can see that only 15 of the 44 were symptomatic.
Also, serious cases such as admission to a hospital should be categorized.
"The researchers detected 44 potential reinfections in the positive cohort, 15 (34%) of which were symptomatic. Some 42 were defined as possible (two positive PCR samples 90 or more days apart, or a new PCR positive at least four weeks after an antibody positive result), and two were defined as probable (additionally required quantitative serological data or supportive viral genomic data)"
How much immunity does Covid 19 infection give?
That depends upon how "immunity" is specifically defined.
Competing interests: No competing interests