Liam Fox is a former Secretary of State for International Trade, and is MP for North Somerset. He is currently writing a book on pandemics.

Sars CoV-2, the virus that causes the clinical illness Covid 19, started to spread around the world from its origins in China in December 2019 – although the date is somewhat speculative because of the delay in Chinese reporting. Since then, the world has literally lost trillions of dollars in economic output and tens of thousands of lives have been lost.

The response of most governments has been to lockdown its citizens to, in effect, reduce population interactions with a view to slowing the spread of the disease. The most notable exception to this is Sweden, where the emphasis is on the responsibility of individuals to maintain social distancing and good hygiene. Businesses and some schools there remain open based on a very different model from that which has been followed in the UK, originating in Imperial College. The whole world will be watching the respective outcomes.

We know that we cannot keep the economy in lockdown permanently, as a much smaller GDP will mean that we have less money to spend on crucial services, including the NHS and, if extended, may have its own impact on mortality rates. So both the government and the British people want the lockdown to end as quickly as possible, but we are operating in an environment where we lack some of the most important pieces of data in order to make informed policy choices.

For example, we have no idea what proportion of the population may actually have been infected by the virus. When we talk about the number of Covid cases in the country, we are talking only about those who have tested positive. We know next to nothing about the rest. A number of studies in other countries have shown a sizeable proportion of people have had only minor, if any, symptoms. This potentially means that there are potentially large numbers who already have immunity from the virus and could be returning to work.

We also do not know how many people have actually died of Covid-19 and how many people have died with it – in other words, how many of those who have died after contracting Covid-19 would have died of seasonal flu or of the underlying health conditions that many of them have.

There is unavoidably a choice about the optimum speed with which we get the economy and society moving again balanced against public health, remembering that every death is a tragedy leaving behind grieving partners, families and friends. So how do we unwind the lockdown?

I think it is worth repeating some of the science, with apologies to those for whom this is teaching granny to suck eggs. Viruses are composed of two main building blocks. The first is genetic material (DNA or RNA), which will be injected into the host cell as part of a “hijack and occupation” operation. This will result in replication of the virus inside the host cells themselves. The second, a protein shell, is involved in physically breaking into the host cell and providing the basis for replication once the operation is complete. Many animal viruses also have a lipid membrane that surrounds the protein element, which helps protect the virus. This is true of the coronavirus and, since lipids are part of the same group that includes fats, this is what makes it vulnerable to contact with soap – hence the importance of handwashing.

Once inside the cells of the host, the immune system may not be able to “see” the virus and recognise that infection has occurred. To overcome this, cells display pieces of protein from inside the cell upon the cell surface. If the cell is infected with a virus, these pieces will include fragments of proteins made by the virus. A viral protein is a potential antibody specified by the viral gene that can be detected by a specific immunological (antibody) response. Immunoglobulin M (IgM) is the first antibody to be made by the body to fight a new infection and has broad activity within the first few days. Immunoglobulin G (IgG), the most abundant type of antibody, is more specific for the virus and more potent, but it takes a few weeks after the infection to develop.

Antigen testing looks for the presence of the genetic material (RNA) of SARS-CoV-2. The test is highly sensitive and specific, but it can only identify patients with active infection because the viral genes are quickly degraded.

Antibody testing, on the other hand, will determine if an individual has been exposed to COVID-19 infection previously, and IgG antibodies may indicate immunity to subsequent infection by the same virus. Hence antibody tests would provide critical information, because they would almost certainly predict whether an individual was immune or susceptible to future Covid-19 The Food and Drug Administration in the United States has issued its first authorisation for a Covid-19 antibody test but none have been approved yet in the UK.

Understanding the advantages and limitations of these tests will be key to utilising them in unwinding the lockdown.
There seem to be two broad models for this process in the absence of a vaccine being available, something that seems at least many months away from. The first model we might describe as the “public health first” model and the second the “economy first” model. In practice, of course, there is likely to be overlap between the two.

In the “public health first” model, the main consideration is the resumption of normal social and economic life without causing a resurgence in the number of serious cases requiring hospitalisation or causing death. This will require both stratification of the population and widespread testing if it is to be effective.

First, the population of needs to be categorised according to the risk they carry themselves and the risk they pose to the rest of the population. Those at highest risk are those recently identified in the Government’s NHS letter – those, for example, who have had transplants, are immunocompromised or have severe underlying conditions such as long-standing respiratory disease.

Next come the elderly especially those who have underlying health issues such as cardiovascular disease, hypertension or diabetes.

Then we have the general population who can, if desired, be broken down into other health risk subgroups. It is arguable that the young should be treated as a separate group as all the evidence suggests that they are much more likely, on average, to have a less severe form of the illness.

Those who have had an antigen test (probably because they exhibited symptoms) which has been positive (and they have been isolated for 14 days) are unlikely to pose a risk to others. This will also be true for those who have had a positive IgG antibody test indicating recovery from infection. These will be the safest to return to work and have a less restrictive social practices. The widespread testing of the population is the key to implementing this.

After these groups, those at lowest risk can gradually be reintegrated while those at the highest risk will need to maintain isolation until a vaccine is available or the rate of infection drops dramatically to what is deemed an acceptable level. In any approach that depends on levels of immunity there will need to be an ability to verify and police those who have had, or claim to have had, the necessary testing. Fortunately, the technical capacity to do this already exists in the UK.

The second model places greater emphasis on the need to get economic recovery underway, based on the argument that we cannot, for the sake of future generations and the long-term impact of a sustained shutdown, continue to prevent the economic activity of our people in order to prevent what is, in historic pandemic terms, a relatively modest risk to mortality.

Since the initial lockdown was justified in terms of not overwhelming limited NHS capacity, especially ICU and the availability of ventilators, it follows that if that capacity has grown and the rate of infection in the population has slowed, then greater public health risks can be justified. Such an approach depends less on mass testing, and could also be rolled out with those in what are assessed as being the most economically necessary areas returning to work first and others in a phased approach.

Whatever model, or hybrid of the models, is adopted or whatever alternative proposal is deemed better, the public need to know that there is an exit strategy in place. The idea that the current lockdown can be maintained for a long period, either socially or economically, is untenable.

Increasingly, people can see the great economic difficulties that may lie ahead as a result of our response so far to the coronavirus outbreak and know that it cannot continue indefinitely. We must also be aware of the social consequences of the lockdown. It is one thing to be confined to home if that home has a spacious garden and quite another if you are living as a family in a crowded flat in an inner city area.

Whatever approach is taken it is highly unlikely that there will be a single point at which the lockdown is entirely lifted, and it is worth preparing the country for the fact that any winding down of the current restrictions is likely to occur on a phased basis. There can be no “declaration of victory” against a viral outbreak, not least because subsequent waves are likely to occur and it is essential that the public are prepared for this.

The Government should be given due credit for its overall approach to this crisis based on the expert advice it has been given,china and deserves our support as it continues to walk a difficult ethical-economic tightrope.