The Covid-19 End Game
This pesky Corona virus is dominating our lives at the moment. There are constant calls to avoid social contact, no touching, no parties, rather little fun. Scott Morrison says it will go on for six months, possibly more. He says there are teams of people exploring the next stage, and then the business restoration stage after that. But what is that next stage and when will it start? What does the exit ramp from this social distancing highway look like? How many exit ramps are there?
There seem to be two ways to the end of the Covid-19 social avoidance rules. There is Herd Immunity where enough people have Covid-19 antibodies that new infections diminish, and by contrast, Containment where most of the population do not get infected. There are three technologies which can steer us into one or the other. There may be vaccines which would allow us to acquire immunity without being infected, treatment drugs which might reduce the impact of Covid-19, and test equipment might allow very wide and frequent testing to occur. Other existing technologies such as ventilators will be crucial to save lives, but do not themselves point towards Containment or Herd Immunity as the end point for the social distancing.
Without a vaccine or treatment drugs, Herd Immunity is a dreadful option. The death rate for Covid-19 is quoted as somewhere between 0.5% and 5%. Cases in South Korea have been growing at about 1% per day, so the number of infected people is probably fairly accurate. The death rate in South Korea is 2% of the reported cases of infection. The Herd Immunity level for this highly contagious disease has been quoted as 2/3rds by WORLDOMETER. For Australia that means 16.7 million of our 25 million people would have to be infected and if 2% of them die, the death count exceeds 300,000. That is roughly double the normal annual death rate. We only lost 40,000 lives in World War II. If this model is applied to the United States of America, the number of deaths from Covid-19 would be more than 4 million, and the US only lost 400,000 lives in World War II.
Without vaccines or drug treatments, the death rate would have to be held down to allow hospitals for operate properly. The present 2,000 Intensive care unit (ICU) beds in Australia might be expanded to 7,000 to allow 5,000 for Covid-19 patients (this has been suggested by the Deputy Chief Medical Officer, Dr Nick Coatsworth), so that an intake of 2,000 per week might be accommodated. If for example, the number of patients in ICU beds is 5% of the number of people recently infected, then we can infect 40,000 per week, and it would take 400 weeks or 8 years to reach the total of 16,000,000 required for Herd Immunity. This is an exit ramp to be avoided.
Vaccines change all that. If someone can produce a vaccine which is effective in 99% of cases, then you can drop the deaths by a factor of 100 down to 3,000. Australia might lose several hundred lives more before the vaccine is available. That’s the problem with vaccines. They take so long to test. You have to check that they are effective in animals and that takes a couple of months. Then you have to ensure that they cause no ill effects when given to people. Lose another month or two. And then you have to check that they really help people who get infected after receiving the vaccine, and that takes more than two months. Finally you have a product and factories have to be built to make it. Many more months go by before it starts to become available.
Bill Gates has said that funds to establish vaccine manufacture whilst human trials are progressing might be available. That could reduce the elapsed time to less than one year, but the testing process only began in March. So it seems unlikely that a vaccine could be available before November and the need in the Northern hemisphere far exceeds that where people are entering summer, so Australians would not get it until February. Unless Australia starts developing its own manufacturing capability as soon as a trial reaches human testing. Given the costs involved, we should have someone like CSL planning manufacture of at least one vaccine. We might be able to resume normal society in February 2021.
Treatment drugs can have a similar impact. If a drug can help 90% of people who would otherwise have needed ICU treatment to avoid that treatment, then it is likely to reduce the death rate by a factor 10. Australia would suffer 30,000 deaths instead of 300,000 to achieve Herd Immunity by this path alone. Too many. Obviously, the fraction of people who are not helped by a treatment drug determines the number of deaths. If it was only 1% whose symptoms were not relieved, then the position is similar to the numbers given for vaccines above, and we would probably have an acceptable off ramp. Given the raging infections in the United States we may learn the effectiveness of any drug treatment without doing any testing in Australia. The time to reach this exit clearly depends on the time to test existing drugs for effectiveness on Covid-19. Mercifully drugs which already have approval can skip the first two testing stages, and the time in the third stage when the immune system is responding to vaccine stimulus, so we might have a drug chosen in a few months. Manufacturing capability is then the issue. In August Australia will be in mid-winter whilst summer will have arrived for the existing Covid-19 hot spots. We might be able to import a treatment drug and start our own manufacture before the winter in the North. We might have an exit from social distancing in October, but only if the drug is effective for almost everyone. Some relaxation maybe, but if there is no other help, it is likely that restaurants will remain shut.
To achieve containment, you need to reduce the effective R0, the number of people infected by every newly infected person. Without any social distancing, R0 is estimated at between 1.4 and 5 although 2 to 3 is more likely. This is much worse than influenza (1.3) which is why you need 2/3rds of the population to be immune to get Herd Immunity. By keeping people apart, we may be able to get the effective R0 to be less than 1.0. However, this model as it stands requires social distancing to continue for a very long time. Without some intervention, every international visitor is a potential threat. Take your foot off the brake and the death truck will start to speed up down the hill to disaster.
There is a possible way to solve this problem. Fast convenient testing. If testing for the infectiveness of any person was easily available and quick, keeping apart could be replaced by testing followed by keeping apart if the test is positive. Any work situation involving being close to others, especially hospitals, would be the first places where this testing would be used. But it could extend to social gatherings given enough testing systems. You could invite 50 people to a wedding. They are all tested and find the results before they arrive, and all those who will not infect anyone else can come. It is a burden, but not as bad as restricting the wedding to 5 people. Automatic testing systems in shopping plazas and railways stations could reduce infection rates hugely. They might print a green ticket for those whose breath carries no Covid-19, and you put that ticket in an arm band for all to see. Sounds impossible. Well Abbott Industries claim they have devised a portable test unit called ID-NOW which does the main part of that.
They say it can produce a result in 13 minutes, faster if it is positive. If that device were to be manufactured in volume in Australia under licence to Abbott Industries, it could revolutionise social distancing. Once you can check people quickly and conveniently, you can do better than getting everyone to stay home. You might even be able to get airline and cruise ship bookings.
It might take 4 months to set up the factory and the Intellectual Property agreements. If you could make 100,000 units a month, you could start to gradually relax social distancing, when combined with testing before Christmas, with the prospect of end it all before May 2021. We should be exploring this option right now.
We can be sure that Containment becomes less and less viable as the number of infected people grows, because the need for the testing grows with that number. You can force the outcome to be Herd Immunity by ignoring the pleas of the medicos.