Experts give feedback to ‘pingdemic’. What should we do against wave after wave of Covid-19?

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.

“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.”

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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 coronavirus.data.gov.uk 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 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.”

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