The UK Well being Safety Company – whose predecessor, Public Well being England, employed me for a decade and a half – launched a overview final week, wanting on the ‘effectiveness of non-pharmaceutical interventions to scale back transmission of Covid-19 within the UK’.

Some commentators have written about this as if it’s a definitive evaluation of the efficacy of various lockdown measures. However that’s not the case. This ‘mapping overview’ is only a trawl by UK research which have investigated the impression of the non-pharmaceutical interventions (NPIs) that have been inflicted upon us between early 2020 and the beginning of 2022.

It doesn’t appraise the standard of the fabric. The UKHSA’s fishing journey discovered some 151 research, 31 of them by UKHSA authors. An astonishing two thirds – 100 – have been based mostly on modelling solely. Simply 22 have been observational and solely two concerned trials to check particular interventions (and trivial interventions at that).

That is removed from superb working materials, and the authors notice that it ‘offers weak proof by way of examine design, as it’s primarily based mostly on modelling research, ecological research, mixed-methods research and qualitative research’.

Sometimes, the overview is oddly coy, particularly on the effectiveness of ‘face coverings’, the place it merely notes an ‘proof hole’. This ignores the conclusions of January’s Cochrane Evaluation – extensively thought of the gold commonplace of systematic evaluations – on ‘Bodily interventions for respiratory viruses’ (most likely as a result of it was not UK-specific). However, the Cochrane Evaluation adjudged that there was no substantive cause to imagine that masks are efficient. Not even the surgical N95 masks.

In brief, the standard of the fabric recognized by the UKHSA is poor. However, whereas evaluation is ongoing, the research clearly don’t present overwhelming proof of NPI efficacy. In any other case, you will be positive we’d have examine it, given the authorities’ and huge components of the media’s assist for lockdowns.

There’s a deeper downside for the overview, nonetheless, if the UKHSA’s intention is to develop a idea on how greatest to manage SARS-CoV-2. Particularly, Covid-19 was and is a altering virus. Which means the effectiveness of interventions alters over time, often diminishing. Anybody doubting this could contemplate China, the place stringent NPIs suppressed SARS-CoV-2 for a lot of 2020 and 2021, however failed spectacularly as soon as the Omicron variant took maintain in 2022. What labored in opposition to the early virus failed in opposition to its successors.

Moreover, NPIs themselves possible speed up a virus’s evolution. Evolution entails two distinct occasions. First, a random step to generate change. Second, a non-random step, wherein the surroundings favours variants with helpful adjustments. Within the case of SARS-CoV-2, random errors happen regularly because the virus’s RNA genome is replicated by contaminated human cells. Most adjustments are deleterious, producing variants that swiftly die out. However just a few adjustments improve the virus’s potential to contaminate new hosts. Variants with these adjustments then unfold.

And right here’s the vital level: by constraining the mum or dad virus, a semi-effective NPI may due to this fact assist new variants. It may, for instance, encourage the unfold of variants which might be higher capable of move by masks.

It’s useful right here to differentiate two types of NPIs: those who construct a wall and those who create a bottleneck. An instance of a ‘wall’ NPI is using condoms as safety in opposition to sexually transmitted infections (STIs). There’s nothing an STI pathogen can do to cross the wall, and condoms exert no selective stress.

In contrast, the NPIs used in opposition to Covid created bottlenecks, not partitions. Lockdowns meant that when you met fewer individuals, you continue to met some. Masks might have filtered some virus particles, however many handed by. Social distancing might have protected you from coughed droplets, however a lot much less so from virus-laden aerosols. These NPIs exerted ‘selective stress’ on the virus, encouraging variants that permit it to transmit extra effectively.

I imagine that an instance of this course of was seen throughout the UK’s second lockdown, in November 2020. Whole Covid instances in England drifted downwards from 20,000 per day initially of the month to 12,000 on the finish. Nevertheless, instances in Medway and Swale (each in north Kent), grew remorselessly from early October to the tip of December, regardless of the November lockdown.

Critically, Medway and Swale have been the epicentre of the emergence and early unfold of the Alpha pressure, or the ‘Kent’ variant because it was initially known as. As soon as lockdown was eased, this NPI-honed variant was prepared to brush Britain after which the world. Which it did throughout December and January.

The brutal conclusion is that, confronted with a mutable virus, bottleneck NPIs won’t solely fail. They will even hone the virus. You may briefly pressure the R quantity (the common variety of new victims contaminated by every case) to under one. However the pool of recent victims stays, and a brand new, extra spreadable variant will emerge by probability and discover a strategy to attain them. Making use of NPIs extra strictly, as in China, simply results in a much bigger closing blowout.

The one uncertainty is how swiftly such NPIs will fail. However make no mistake, they are going to fail. And it’s excessive time we realised this. The lockdown experiment must not ever be repeated.

David Livermore is a retired professor of medical microbiology.