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expert reaction to the ‘pingdemic’

There have been several media reports discussing the impacts of the high number of isolation alerts being received from the NHS Covid-19 app, dubbed the ‘pingdemic’.


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:

“We are experiencing another wave of the Covid-19 pandemic – the third or the fourth, depending on what you count as a wave. And the government in England has relaxed the legal restrictions imposed to limit spread. It is not clear if the new guidance is actually lawful.1

“It may be that people will continue to behave in such a way as to limit spread – reducing contact with other people, maintaining distance, wearing a mask in enclosed spaces, and so on. But the relaxation of these legal restrictions and the message it sends – that Covid-19 is no longer a serious risk (although it is!) can be expected to mean that at least some people will, slowly or quickly, return to pre-pandemic behaviours, thus facilitating further transmission.

“The Covid App is designed to alert people when they have been in significant contact with somebody who has been identified as a case (and thus at risk of having been infected).

“Of course, many cases will not have been identified as such, so some who have been exposed won’t be alerted, meaning that some infectious people will not have been advised to self-isolate. I have also heard suggestions that the app may have alerted some people who did not actually have significant contact with a case; but I think we have to assume that most of the time it works as it should.

“What has changed, since the app was introduced, on the plus side, is that:

  • A large number of people have been vaccinated.
  • Cheap, widely available (albeit not very sensitive) tests have become available.

“On the other hand, we have also seen:

  • The introduction and widespread replacement of previous variants by the far more infectious alpha and delta variants.
  • The now-prevalent delta variant, in contrast to previous variants, is poorly prevented by a single dose of vaccine.

“We should also have better data on what proportion of the contacts actually go on to become infected and infectious.

“Because the pandemic, and in particular the delta variant, has been allowed to enter the country and spread out of control, there are now many, many cases of Covid-19. Because of the vaccination programme, fewer of them than previously are seriously ill, requiring hospital or ICU admission, or dying; although the vaccines are not and never will be 100% effective at preventing such severe outcomes, and even if only a small percentage of fully vaccinated cases require hospital admission or die, given the massive number of cases, the actual numbers will be high.

“With the delta variant being so much more infectious, people who are not immune – they have not (yet) been fully vaccinated (which means it’s at least 14 days after the second dose), or for some reason the vaccine hasn’t worked for them – are much less able to avoid infection.

“Changes to risk and exposure, and the initial focus on ensuring older people were vaccinated, means that a higher proportion of the cases who are seriously ill or die are younger than in previous waves – clinical colleagues comment on the relatively high proportion of cases admitted to hospital, to ICU, or dying being in younger age groups.

“So the app, which is designed to ensure people who have been exposed and who are potentially infectious, self-isolate until we can be sure they are not infectious, is still an important part of our armoury to control the pandemic; and we must still do what we can to limit the pandemic.

“With so many people being exposed, however, this does put pressure on society’s ability to provide essential services.

“It is possible, now that so many people have been fully vaccinated, and given the availability of testing, that the risk of transmission might be low enough to permit people who have been “pinged” to work in certain circumstances.

“We need to consider, for example:

  • How much less likely is somebody to be infected and infectious following exposure if they are fully vaccinated?
  • How much less likely is somebody to be infectious if they have a negative test – at the time of the test, and until their next test?
  • Do other mitigations (such as requiring them to wear an FFP2 or better mask while working) further reduce the risk?

“These are not simple questions, and answering them will require some assumptions to be made which are based on a “best-guess” rather than good quality data.

“Balancing the need to keep society moving by not preventing key-workers from doing their jobs, while at the same time not fuelling the pandemic by allowing infectious workers to infect others and mean many are seriously ill, requires difficult judgements.

“We must hope that the decisions that have been made are well founded; and that the effect the measures used to reduce the likelihood of infection are at least as effective as the decision-makers have estimated them to be.”


  1. Wagner A. @AdamWagner1: Still don’t really understand the legal basis for this if workers are avoiding test and trace notifications (not just the app). Is it all “research”? Is there guidance on it somewhere? Twitter thread 2021; Updated 23 Jul 2021; Accessed: 2021 (23 Jul): ( or


Prof Allyson Pollock, Clinical Professor of Public Health, University of Newcastle, said:

“The problem is the government is committed to a policy of unevaluated mass testing for the population. This together with the app is causing enormous harms as the yield of cases for the enormous number of people isolating will be very small.

“The virus is endemic and reinfection with different variants will likely become common place but it is likely that for most people ie. those who have had prior infection or have had vaccination or children infections will be mild, no worse than the common cold. This is evidence from the much lower hospitalisations and deaths.

“A much more sensible strategy would be: for testing to be reincorporated into clinical diagnosis in health services, for people with symptoms to stay at home and isolate and for the government to consider a much more targeted test and contact tracing strategy for high risk groups.

“This strategy must be evaluated to look at the yield, the harms costs and benefits and extent to which transmission is reduced. 

“The current policy of mass testing and the NHS app, mandatory vaccination of careworkers, mass isolation, covid passes and covid passports are unnecessary and disproportionate.  Commercial interests are trumping public health.”


Dr Simon Clarke, Associate Professor in Cellular Microbiology at the University of Reading, said:

“The number of pings from the app has been increasing because more people are infected with the coronavirus.  The best way to bring down the number of pings would be to bring down the number of infections and the idea that this is a problem with a faulty app which just needs to be binned is nonsense.

“While it may very well be necessary to allow more people who have been contact traced by the app to avoid isolation, this is not without substantial risk. It is entirely possible that many people will test negative but still be infectious. In the NHS staff carrying the virus will interact with patients, some of whom will have failing immune systems.  In other workplaces it could lead to infection of the working environment or perhaps even goods that are being handled and it remains the case that items being shipped to supermarkets could well be handled by someone with the coronavirus.  Studies in the United States1 showed that without thorough cleaning, surfaces in workplaces can remain an infection risk, once contaminated, for up to 3 days.”



Dr Penny Ward, Faculty of Pharmaceutical Medicine, Visiting Professor in Pharmaceutical Medicine, Kings College London, said:

“Several strands of evidence suggest that the small proportion of individuals that become infected despite having received a complete vaccination course will be less likely to transmit infection to contacts, not least the observed reductions in viral load in PCR positive vaccinated individuals, reduced length of virus shedding in these individuals and finally an estimated 60% reduction in spread to unvaccinated contacts within the same household. These observations support the conclusion that completely vaccinated individuals represent less danger for spread of infection. COVID is most readily spread within close contact environments. In the early epidemic, when there was limited access to testing, and vaccines were not available, it was reasonable to advise individuals in contact with a case to self isolate until a time at which they would be unlikely to be a risk to others. However in the ‘new’ post vaccinated world, not only are these individuals less likely to become infected in any case, but also would be less likely to transmit even if infected. This then suggests that it would be very reasonable to permit fully vaccinated individuals to continue to work as long as they can undergo PCR testing test negative. In contrast, the issue of complete exemption from requirements to isolate if completely vaccinated must also take into consideration the circumstances in which the individual operates. If they are likely to be in close contact with vulnerable individuals it would be reasonable to expect that they would be undergoing regular testing as a routine and would still be required to isolate if they test positive; this approach takes into account potential variations in vaccine protection as new strains emerge.”


Dr Stephen Griffin, Associate Professor in the School of Medicine, University of Leeds, said:

“I find the use of the term “pingdemic” incredibly unhelpful and potentially damaging as it minimises the seriousness with which we ought to approach the control of a potentially dangerous infectious disease.  This has no basis in scientific method and merely reflects a biased perspective that is further undermining our pandemic response.

“The reason that so many people are receiving notifications is simple, we have a highly transmissible virus that is being allowed to spread throughout the country with the bare minimum of mitigation.  The tracing of close contacts for those knowingly infected and/or exposed to the virus is a mainstay of infection control.  As set out in our joint letter to the Lancet, allowing mass infection is a dangerous experiment, so to do away with what essentially constitutes our last line of defence against the spread of SARS-CoV2 should not be considered as any sort of reasonable option.

“The idea of exempting double-vaccinated individuals is also a mistake in my opinion, regardless of what sector they might work in.  We know vaccines are somewhat less effective at preventing infection compared to their protection from severe disease.  Delta makes this all the more challenging as it can partly evade some antibody responses.  This means that individuals can potentially be infected and infectious, whilst potentially being unaware that they are a carrier; this could also be difficult to spot using lateral flow tests as they are less sensitive than PCRs, confirming that these are a red, not a green light option.  We must remember that only just over half of the country has had both vaccine doses, and so many younger and/or vulnerable people remain at risk.  We also do not understand whether those infected following vaccination might be susceptible to long COVID, although one assumes this is far less likely than following natural infection.

“One cannot help but perceive a growing attempt to minimise the impact of infection here in the UK, what with the dissolution of school bubbles, talk of turning the app down, or even off, and exempting people from contact tracing.  Some have even suggested that the data on the DHSC dashboard ought not to be public.  You cannot manage an epidemic without understanding disease prevalence – this much is patently obvious.  Whilst less attention to outbreaks may become acceptable in a future where our country is properly protected by sufficient vaccine coverage, this is clearly not the case at present.  If the government and industry are upset or inconvenienced by people having to isolate, then might I politely suggest that they deal with the root of the issue rather than merely ignoring the fact that we have essentially created this latest wave ourselves as a result of not coupling the roadmap to the vaccine programme.  Moreover, with the unfortunate decision not to offer routine vaccinations to teenagers at present, it is difficult to see how our vaccines will eventually fulfil their potential of restoring life to as near to normal as possible.

“Lastly, we must also remember that COVID does not exist in a vacuum.  There are is an enormous backlog of NHS activity to clear, plus autumn looms with an already obvious resurgence in other respiratory conditions that are literally turning summer to winter in terms of hospital capacity.  With the link between infection and hospitalisation only weakened, the prospect of even higher infection rates, and these other imminent challenges, I fear that the lack of caution and patience inherent to our unlocking will result in a profound cost in terms of suffering, NHS pressure and economic impact.  This is simply not something that can be ignored or dismissed with a trivial nickname.”


Prof Kevin McConway, Emeritus Professor of Applied Statistics, The Open University, said:

“It’s not at all surprising there are so many pings.  The counts of new confirmed cases on the dashboard at are at levels that were only as high as they are now, in times after the app was released, between the last few days of December 2020 and mid-January this year.  But, back then, people weren’t mixing nearly so much – there were lots of restrictions throughout that time and a pretty well full lockdown for most of it – so people weren’t contacting others nearly so much as they are now.  Also, at that time, the alpha variant was becoming dominant, and though we were (rightly) concerned about that at the time, it’s not as easy to pass on as the delta variant that is dominant now.  So people were much less likely to come into contact with an infected person back then, and, for unvaccinated people even if they did, the chance that they’d catch the virus was quite a bit less than it would be now.  Vaccines do reduce the chance of catching the virus considerably, but they don’t reduce it to zero by any means, and there are still substantial numbers of people who aren’t fully vaccinated.  So we’ve now got numbers of infected people not much less than the peak at the turn of the year, more mixing so more opportunities for infection, and a more infectious variant.  No surprise there are so many pings now, compared to then.”


Prof Sheila Bird, Formerly Programme Leader, MRC Biostatistics Unit, University of Cambridge, said:

“We need better-performing antigen lateral flow tests than the 7-packs issued in UK.  Hence, three actions are critical:

  1. We need LFT-screen-positives rapidly to access PCR-test for adjudication (not least so that their NHS T&T contacts can be stood down if the confirmatory-PCR test is negative). The % LFT-positives subject to adjudication is not yet 80%.
  2. We need those pinged (or tracked by other means) as close contact speedily to seek PCR-test [LFT is not good enough] because, if positive, then NHS T&T can get to work more quickly on alerting their contacts.
  3. We need transparency from NHS Test & Trace about how efficient NHS Test & Trace is at rolling back its instruction to self-isolate if an LFT-positive index case turns out to be PCR-negative within 2 days.
  4. Unless superbly efficient, those contacts may be sentenced to up to 7 days of needless self-isolation.
  5. Hence, NHS T&T: where are your performance statistics?”


Prof Paul Hunter, Professor in Medicine, The Norwich School of Medicine, University of East Anglia, said:

“Recent news reports of the impact that the current “pingdemic” is having on British society and especially what it could have on our essential services and food security is very concerning.

“The first thing to say is that any single measure whether it be self-isolation, quarantine, mask wearing, or any one of the other restrictions that we have lived under the last year will have some impact on reducing disease transmission.  But non single measure will be sufficient to bring transmission below 1 in a largely unvaccinated population.  For any measure we may wish to implement we should ask ourselves whether the benefits of that measure outweigh the negative impact.

“There have been several modelling studies looking at the benefit of contact tracing and quarantine of contacts on reducing transmission of COVID, in general they have found some benefit though the additional benefit over self-isolation of just cases has not been great and critically depends on high compliance with requests to self-isolate.  We also know that full compliance with requests to self-isolate are frequently ignored.

“Most of these studies were conducted prior to roll out of vaccine and at a point in the pandemic when few people will have had any immunity from natural infection.  Since then over 2/3 of adults have been fully vaccinated and almost 90% have had a single dose.  Even amongst non-vaccinated individuals a substantial proportion will have immunity from a natural infection.  There is also good evidence that if you have been vaccinated and still get infected then you shed much less virus and will not be as infectious.  This also applies to people who have re-infection following a natural infection.

“But not all contacts are equal, and we have to distinguish close family contacts of a known case with casual contacts with strangers.  Yes, you can get infection transmission in both settings, but it is far more likely in family contacts than in random casual contacts.

“What this means is that the benefit of quarantine of contacts which was never great will be even more marginal now and probably extremely low for casual contacts, the type of contacts that we are informed about through the pings from NHS direct.  This extremely low benefit for quarantine of casual contacts will be pretty much zero if you are fully vaccinated or have recovered from a previous known infection with COVID.

“To my mind it is very clear from the available evidence that the current requirement to quarantine following being pinged because you are a casual contact has little if any value in controlling the epidemic in the UK, especially if the person being pinged has been fully vaccinated or has recovered from a proven natural COVID infection.  I can see no value in waiting another four weeks to lift this requirement and I would support this being lifted tonight.  Although I would argue against the need to quarantine for people who are fully vaccinated or who have had a confirmed COVID infection if pinged by the app, continuing to use the app would enable people to make informed choices such as when visiting particularly vulnerable friends or relatives and so I would counsel against deleting it.  And these comments do not apply to other closer and especially family or household contacts where the balance of evidence does still support the need to quarantine if you are a contact.”


Prof Jon Crowcroft FRS FREng, Marconi Professor of Communications Systems in the Computer Laboratory, University of Cambridge, said:

“Pings are proportionate to positive PCR test results and contacts that people made where they were within 2m for more than 15 mins.

“So the test +ve rate went to 50k a day for nearly a week so 500,000 pings represents about 10 contacts per +ve case (or roughly one a day).  BUT you have to allow for the fact only 20M out of all adults have the app running – so say 25% chance of contact between people with app.  So you’d need about 4 contacts a day – if most these are in public transport and pubs, this is pretty unsurprising (typical crowd in a pub might involve 5-10 people at a table watching footie).

“6% of contacts lead to infection, so we might infer about 30,000 infections out of the pings.  Note there are therefore actually 4 times that many actual infections (i.e. ones from contacts between people not running the app) – i.e. about 120,000 new cases, which will show up about 5-7 days after the contact so sometime this weekend, we might predict 120,000 cases.  BUT 65% of people are vaccinated – let’s take double dose cases: about 2/3 chance of infected person being vaccinated and 2/3 chance of contact being vaccinated.

“Evidence says that vaccination reduces transmission by 2-4 times, and so about 50% of those contacts that might have led to infection, won’t.  So the 6% is reduced to about 3% perhaps, so the more plausible prediction is perhaps 60,000 new cases this weekend.

“Take all that with a large pinch of salt.

“Calls to reduce the sensitivity of the app are totally misguided – it would be totally pointless running it then.

“Calls to change the advice to people on what to do when pinged are much more sensible.  If you are vaccinated (or previously had covid), then the sane advice would be to do 2 tests for two successive days (even lateral flow).  You go back to work, but test for 2 days – if both tests negative, stay at work.  If either test positive, isolate.”



All our previous output on this subject can be seen at this weblink:



Declared interests

Dr Peter English: “Dr English is on the editorial board of Vaccines Today: an unpaid, voluntary, position. While he is also a member of the BMA’s Public Health Medicine Committee, this comment is made in a personal capacity.”

Dr Penny Ward: “No COIs. I am semi-retired, but I am owner/Director of PWG Consulting (Biopharma) Ltd a consulting firm advising companies on drug and device development.  Until July 2019 I was Chief Medical Officer of Virion Biotherapeutics, which was a company developing broad spectrum RNA therapy for the treatment/prevention of respiratory virus infections.  Between December 2016 and July 2019 I served as Chief Medical Officer of Virion Biotherapeutics Ltd, a company developing antiviral treatments for respiratory viral diseases.  Previous employee of Roche, makers of tocilizumab (anti IL6 antibody) and CMO of Novimmune, makers of empalumab (anti IFN gamma antibody).  These are my personal views and do not reflect those of either institution.”

Dr Stephen Griffin: “No conflicts.”

Prof Kevin McConway: “I am a Trustee of the SMC and a member of its Advisory Committee.  I am also a member of the Public Data Advisory Group, which provides expert advice to the Cabinet Office on aspects of public understanding of data during the pandemic.  My quote above is in my capacity as an independent professional statistician.”

Prof Sheila Bird: “SMB does not have the type of phone that accepts apps and so can’t be pinged. SMB is a member of the Royal Statistical Society’s COVID-19 Taskforce and chairs its RSS/DHSC Panel on NHS Test & Trace.

SMB is a member of RSS Working Group on Diagnostic Tests which reported on 9 June 2021 and made 22 recommendations on study-design matters (10), regulation (6), and transparency matters (6).”

None others received.


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