Альтернативное мнение о британской антивирусной стратегии

Тупо скопипащу, а в следующем посту сделаю краткие выжимки со своими комментариями и свежими мыслями. 

ЗЫ.  Поскольку гугл переводит главное тут понятие herd immunity то как стадный иммунитет, то как иммунитет стада, то поясню,  что данное понятие означает, что после того, как не менее 70% популяции приобретет иммунитет к какому-то вирусу, он перестает распространяться. Поскольку в коментах к предыдущим постам британская стратегия была одобрена большинством читателей,  интересно познакомиться с тем, что эта стратегия означает на практике.  Гугл-переводчик в помощь тем, кто еще не превзошел.

 The UK government recently enacted its second phase of response to the COVID-19 pandemic: “delay”. According to ITV journalist Robert Peston,  the government’s strategy to minimise the impact of COVID-19 “is to  allow the virus to pass through the entire population so that we acquire  herd immunity, but at a much delayed speed so that those who suffer the  most acute symptoms are able to receive the medical support they need,  and such that the health service is not overwhelmed and crushed by the  sheer number of cases it has to treat at any one time”. At face value,  this seems like a sound strategy, but what exactly is herd immunity and  can it be used to combat COVID-19?

Our bodies fight infectious diseases through the actions of our  immune systems. When we recover, we often retain an immunological memory  of the disease that enables us to fight off that same disease in the  future. This is how vaccines work, creating this immune memory without  requiring getting sick with the disease. 

If you have a new disease, such as COVID-19, that we don’t have a  vaccine for and no one in the country has ever been infected with, the  disease will spread through the population. But if enough people develop  an immune memory, then the disease will stop spreading, even if some of  the population is not immune. This is herd immunity, and it is a very  effective way to protect the whole of a population against infectious  disease. 

But herd immunity is typically only viewed as a preventive strategy  in vaccination programmes. If we don’t have a vaccine – as we don’t for  COVID-19 – achieving herd immunity would require a significant  proportion of the population to be infected and recover from COVID-19.  So what would this mean for the spread of the disease in the UK?

The percentage of the population that needs to be immune to enable  herd immunity depends on how transmissible a disease is. This is  measured by the term R0, which is how many new infections each case will  generate. For COVID-19, the R0 is estimated to be 3.28,  though studies are still ongoing and this number will probably change.  This means that for herd immunity, about 70% of the UK population would  need to be immune to COVID-19. 

Achieving herd immunity would require well over 47 million people to  be infected in the UK. Current estimates are that COVID-19 has a 2.3% case-fatality rate and a 19% rate of severe disease.  This means that achieving herd immunity to COVID-19 in the UK could  result in the deaths of more a million people with a further eight  million severe infections requiring critical care.

Novel coronavirus in 3D by Fusion Medical Animation. 

Delay as a public health strategy

However, it is not clear how much of this discussion of herd immunity – reportedly proposed by David Halpern, chief executive of the Behavioural Insights Team, and later blogged about by Robert Peston – is actual government policy. 

Also, the concept as discussed is not simply to let the disease run  its course through the population, but to slow its spread and protect  those most vulnerable from severe disease. 

Slowing the spread of COVID-19 is a promising strategy, especially  when combined with enhanced measures to protect the elderly and those  with underlying health conditions. By slowing the spread of the disease,  the NHS might have more time to prepare, we might be able to develop  treatments or vaccines and we will be closer to the summer when we have  lower incidences of other diseases that burden the NHS, such as the flu.  

A delay strategy when combined with surveillance and containment, as recommended by the WHO,  could be very effective in combating the spread of COVID-19. Yet if we  slow the spread of the virus but are relying on herd immunity to protect  the most vulnerable people, we would still need 47 million people to be  infected. 

Even if we manage to protect the most vulnerable people (though no  discussion is provided on how this will be done or for how long) the  fatality rate for the otherwise healthy portion of the population may  still be 0.5% or higher. This means that even in this unlikely “best case” scenario we would still be looking at more than 236,000 deaths. 

We can and we must do better than that. China is rapidly controlling the spread of COVID-19 without requiring herd immunity (only 0.0056% of its population has been infected). Waiting for herd immunity to COVID-19 to develop in the UK by letting the virus “pass through the community” is not a good public health strategy.