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Covid-19: four fifths of cases are asymptomatic, China figures indicate

BMJ 2020; 369 doi: (Published 02 April 2020) Cite this as: BMJ 2020;369:m1375

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Rapid Response:

Amidst the cacophony, don't forget the advice of Tom Jefferson, Carl Heneghan, Els Torreele and others.

Dear Editor

I cannot get the words of Tom Jefferson and Carl Heneghan out of my head: “Lockdown is going to bankrupt all of us and our descendants and is unlikely at this point to slow or halt viral circulation as the genie is out of the bottle.” (Day, BMJ 2020;369:m1375, April 2) Seven months later their opinion was unchanged: “…lockdowns do not work in the long run; they just kick the can down the road. Meanwhile, ever-increasing restrictions will destroy lives and livelihoods.” (, Oct 31) Their opinion is not isolated; it is shared by other distinguished experts, but is invisible amidst the cacophony of headlines about “waves…surges…spikes…deaths…variants…” Now the headlines are promising salvation in the form of vaccines produced by Pfizer and Moderna. In the US we are being told to hold on until the vaccines are widely distributed: 100 million…200 million…300 million people vaccinated to achieve herd immunity. Is this really the way to go? Here are some questions:

1) How effective are the vaccines? We do not know. Peter Doshi has been a real bird-dog about this. His recent review indicates that Pfizer’s vaccine may be only 19% effective, instead of the “95% effective” so widely publicized. (Doshi,, 4 Jan 2021) Furthermore, there is no evidence that the vaccines save lives or interrupt virus transmission. (Doshi, BMJ 2020;371:m4037, Oct 21)

2) How does Covid-19 vaccine immunity compare with natural immunity from the infection? Again, we do not know. How long will immunity last? How broad will it be? Remember that annual influenza vaccination has been a double-edged sword because it subverts the broad and lasting protection provided by the infection. (Bodewes et al, Lancet Inf Dis 2009;9:784. J Virol 2011;85:11995) Are we now headed for annual Covid-19 shots? Els Torreele may have had flu shots in mind when he warned that we were setting the bar for Covid-19 vaccines too low and were redefining the concept of vaccines from long term public health tools to population-wide suboptimal chronic treatments, good for business but bad for public health. (Torreele, BMJ 2020;370:m3209, Aug 18) The unfortunate history of influenza vaccines should give us pause before we get stampeded into universal Covid-19 vaccination. (

3) What is the real Herd Immunity Threshold/HIT? 60-70% population immunity to halt the pandemic is the figure most frequently publicized, but in the US experts like Anthony Fauci have been quietly increasing the figure to 75…80…85…90%. (McNeil, NYTimes, 12/27/20) Other experts suggest the HIT may be as low as 10%. ( ( ( The appearance of the B.1.1.7 variant may change things, but our CDC offers no HIT estimate and says that “experts do not know.” (NYT 12/27/20) Anthony Fauci has been criticized for “moving the herd immunity goal post to promote policy goals.” (Vinay Prasad. Op-Ed: Why Did Fauci Move the Herd Immunity Goal Posts? Dec 29, 2020)

4) What about symptom-free but test-positive individuals? Is their quarantining an example of overkill? Household transmission by such individuals is only 0.7% in the US. (Madewell et al, JAMA Network Open.2020;3(12):e2031756, Dec 14) In a study from Wuhan no viable viruses were found in any of 300 such individuals and there was no evidence of asymptomatic transmission. (Cao et al, Nat Commun 2020;11:5917. Griffin, BMJ 2020;371:m4695, Dec 1. Pollock & Lancaster, BMJ 2020;371m4851,Dec 21)

5) Is a positive PCR sufficient to diagnose a case of Covid-19? It is in the US (CSTE, 4/5/20. CDC, National Covid-19 Case Surveillance, 8/28/20), yet the overwhelming majority of positive PCRs are found in individuals who harbor no live viruses. ( A large group of international experts has demanded the retraction of a prominent article supporting the use of PCR for Covid-19 diagnosis, citing 10 fatal flaws. (Review report Corman-Drosten et al. Eurosurveillance 2020, submitted 27 November 2020)....PCR massively amplifies dead fragments of viral RNA; it is exquisitely sensitive and subject to contamination, leading to vast numbers of false positives, massive over-diagnosis of Covid-19 illness, and unnecessary quarantine of millions of healthy people. (Yeadon,, 11/30/20. Andrews,, 11/27/20)….Covid-19 is most contagious in the first 5 days after symptom onset, but beyond day 9 of the illness live viruses are not recovered. However, PCR tests remain positive for as long as 12 weeks in respiratory secretions and 18 weeks in stool. (Cevik et al, Lancet Microbe 2020, Nov 19. BMJ 2020;371:m3862, Oct 23)

6) How many deaths have been certifiably caused by Covid-19? We do not know. At one time case reports of infections in medical journals required certification by a positive culture or a rise in antibody titers, but these criteria are not the basis for case numbers reported in today’s headlines. Without such specifics we can only guess at causes of death….For weeks 8 through 49 in 2020 there were 2,620,553 US deaths reported from all causes, an excess of 389,054 deaths compared with the three-year average for the same period in 2017-19. For weeks 8 through 49 286,597 Covid-19 deaths were reported. (CDC, Covidview, 12/30/20. NCHS weekly mortality surveillance data 2013-19)….How many deaths from heart attacks or pneumonia were labelled Covid-19 deaths because of false-positive PCRs? How many of the excess deaths resulted from delays in medical care and societal disruption forced by lockdowns? Have we ignored cases and deaths associated with other respiratory viruses? Last March in California 26.1% of nasal swabs in patients with acute respiratory symptoms tested positive for non-Covid viruses and just 9.5% had Covid-19. (Kim et al, JAMA, 4/15/20)

THIS IS WHAT WE NOW MUST DO: Open up society and focus protection on the truly vulnerable. Offer the vaccines to healthcare workers, to the elderly and other high-risk individuals. Our knowledge of vaccine safety and effectiveness is limited, so we should closely monitor the recipients. Do not vaccinate healthy young and middle-aged individuals, but allow the gradual acquisition of lasting population immunity from an infection that is generally mild. Skip the flu shot. We are seeing very little influenza, and the vaccine increases the risk of illness from non-influenza respiratory viruses, probably including Covid-19. ( ….I can’t get the words of Tom Jefferson, Carl Heneghan, Els Torreele, Peter Doshi and others out of my head.

ALLAN S. CUNNINGHAM 11 January 2021

Competing interests: No competing interests

11 January 2021
Allan S. Cunningham
Retired pediatrician
Cooperstown NY 13326 USA <