It looks like the UK is once again setting up a colossal natural experiment which will put wave three of the pandemic into a super-exponential growth phase, says Trish Greenhalgh

“War is peace.
Freedom is slavery.
Ignorance is strength.”
― George Orwell, 1984

On 5 July 2021, Boris Johnson, the UK prime minister, announced that coronavirus restrictions will be rolled back in England from 19 July 2021. Compulsory masks and physical distancing will be abolished, though “personal responsibility” for these measures will be encouraged. There will be no more checking in to pubs or ordering from tables; people can finally re-join the human crush at the bar. Stadiums and festivals may be booked to full capacity. The “work from home” rule will be replaced by arrangements agreed between employers and their staff. Self-isolation will no longer be required for double-vaccinated contacts. Care home residents may have unlimited visitors. 

This announcement has served to further polarise a country that was already deeply divided in—among other things—its views on the trade-offs between infection control and civil liberties. One or two newspapers celebrated the forthcoming “Freedom day” with headlines like “Boris Johnson rips up Covid restrictions” (Telegraph) and “Boris lights lockdown bonfire” (Express). But for much of the rest of the lay media (e.g. The Guardian), the story was that these rules are being relaxed despite scientists’ warnings that this will increase both cases and deaths and encourage the emergence of new variants. 

As Chris Whitty, chief medical officer, pointed out during the press announcement, the pandemic is far from over—indeed, it is currently accelerating. While the link between infection and hospitalisation has been weakened by our successful vaccine programme, it has not been broken. Whitty’s advice is to “act accordingly to limit transmission;” he himself will be wearing a mask when indoors with others.

Ending compulsory restrictions on behaviour while encouraging voluntary ones feels like a variant of the Johnson’s favoured leitmotif of “have cake and eat it,” first introduced to persuade voters that it would be possible to abolish freedom of movement from EU countries, but retain free trade with them after Brexit. As John Clarke pointed out in his critique of the neoliberalism of a previous centre-left Labour government, there is a fine line between “empowering,” “responsibilising” and “abandoning” of citizens by the State. [1] In some situations—such as the speed we drive our cars—where my freedom affects your safety, there are strong arguments that certain “freedoms” should be restricted by law.  

Those debating whether masking in public places should be a matter of individual choice while covid-19 remains prevalent among us should consider the mechanism of transmission of the SARS-CoV-2 virus. Despite dissent from an outlying minority of scientists, the evidence that this virus spreads mainly through the air is strong and consistent. [2-4] Infectious airborne particles transmit most readily when people are in close contact (within 1-2 metres), causing one person to inhale air that another has exhaled. [5] This happens particularly when vocalising (e.g. singing or shouting) or breathing heavily (e.g. in a gym). [6] As time spent indoors increases, infectious airborne particles spread throughout a room, infecting those beyond 2 metres. [2] There is strong evidence that masking reduces transmission from an infected person to others, and moderate evidence that it gives some protection to the wearer. [7]

Careful analysis of super-spreader events such as public singing performances,8 which cannot be explained by any mechanism of transmission except airborne, have shown that such events may be the primary drivers of the pandemic.9 This would explain the phenomenon of over-dispersion of the reproduction number (kappa statistic10)—in other words, most people with covid-19 do not infect anyone else while around 10-20% account for 80% of known cases. [9]

It follows from the airborne nature of SARS-CoV-2 that the best way (in addition to mass vaccination) to reduce its transmission is to use a combination of measures, each of which adds a layer of protection: universal indoor masking, 2-metre physical distancing, controlling room occupancy, limiting the time spent indoors with others, effective ventilation (e.g.  opening windows) or air filtration, and—in the longer term—redesigning buildings to reduce sharing of air among occupants. [2,3,11] 

It also follows that the best way to increase transmission of airborne viruses is pretty much what has just been announced as government policy—abolish physical distancing rules, abandon universal masking, and encourage people to gather indoors in under-ventilated spaces for prolonged periods to celebrate their newfound “freedom.”

I hope I am wrong, but it looks like the UK is once again setting up a colossal natural experiment which will put wave three of the pandemic into a super-exponential growth phase. Given that we appear to be powerless to stop this happening, we should at least ensure that we collect the right kind of high-quality data to document and analyse what unfolds. 

Trish Greenhalgh, professor of primary care health sciences, University of Oxford, UK.

Competing interests: none declared.

See also: Health and wealth in pandemic times: not a zero-sum game

References:

1. Clarke J. New Labour’s citizens: activated, empowered, responsibilized, abandoned? Critical social policy 2005;25(4):447-63.
2. Morawska L, Milton DK. It is time to address airborne transmission of coronavirus disease 2019 (COVID-19). Clinical Infectious Diseases 2020;71(9):2311-13.
3. Greenhalgh T, Jimenez JL, Prather KA, et al. Ten scientific reasons in support of airborne transmission of SARS-CoV-2. The lancet 2021;397(10285):1603-05.
4. Tang JW, Bahnfleth WP, Bluyssen PM, et al. Dismantling myths on the airborne transmission of severe acute respiratory syndrome coronavirus (SARS-CoV-2). Journal of Hospital Infection 2021;110:89-96.
5. Bourouiba L. The fluid dynamics of disease transmission. Annual Review of Fluid Mechanics 2021;53:473-508.
6. Stadnytskyi V, Anfinrud P, Bax A. Breathing, speaking, coughing or sneezing: What drives transmission of SARS-CoV-2? J Intern Med 2021 doi: 10.1111/joim.13326 [published Online First: 2021/06/10]
7. Czypionka T, Greenhalgh T, Bassler D, et al. Masks and face coverings for preventing the spread of Covid-19: a narrative review. Annals of Internal Medicine 2020:doi.org/10.7326/M20-6625.
8. Miller SL, Nazaroff WW, Jimenez JL, et al. Transmission of SARS‐CoV‐2 by inhalation of respiratory aerosol in the Skagit Valley Chorale superspreading event. Indoor Air 2021;31:314-23.
9. Endo A. Estimating the overdispersion in COVID-19 transmission using outbreak sizes outside China. Wellcome open research 2020;5
10. Lloyd-Smith JO, Schreiber SJ, Kopp PE, et al. Superspreading and the effect of individual variation on disease emergence. Nature 2005;438(7066):355-59.
11. Morawska L, Allen J, Bahnfleth W, et al. A paradigm shift to combat indoor respiratory infection. Science 2021;372(6543):689-91. doi: 10.1126/science.abg2025