Facundo Arrizabalaga/EPA Coronavirus: can herd immunity really protect us? 13 mars 2020, 15:12 CET -- -- 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 -- -- 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. -- -- 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 -- 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 -- -- 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. -- -- 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 -- -- 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. -- -- 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 – -- -- 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. -- -- 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. -- -- community” is not a good public health strategy. * Pandemic * Herd immunity * Coronavirus * UK government