In early March 2020, Patrick Vallance told the BBC’s Today programme that the government’s strategy for fighting the Covid-19 outbreak was built around herd immunity, a tried and tested method for managing outbreaks of infectious disease because once a sufficiently large proportion of the population has some form of immunity, acquired either primarily via surviving a disease, and possibly later via vaccination, it becomes impossible for it to spread. Herd immunity worked for smallpox and it worked for measles.
The problem with herd immunity acquired through infection is that it comes at a price: namely that the disease runs riot and there is a degree of mortality and a number of at-risk people will die while the rest of the population has minimal symptoms.
In 1918-19, between 50 million and 100 million people died from “the Spanish flu”, despite the fact that the mortality rate for the Spanish flu is between one and three per cent, broadly in line with Covid-19. The total mortality numbers are shocking largely because of the widespread reach around the globe. Spanish flu, a viral pandemic triggered by H1N1 then disappeared only to resurface in 2009, again spreading around the world but with only a fraction of the death rate because to the far reaches of the planet, but with only a small fraction of the death rate, having a mortality of only 0.001-0.007% so that the death toll was hundreds of thousands around the globe largely because the two versions of H1N1 had different origins, and we had a degree of herd immunity as well as better living conditions than in 1918.
Herd immunity is a concept that comes from the field of zoology. It refers to the ability of a population of animals to resist infection by a pathogen — such as a virus — because a sufficiently large number of individuals within the population have immunity on an individual level so that their immune system can easily form antibodies against a specific infectious agent and it can’t take hold and make them infectious. With herd immunity, transmissibility in a population is dramatically reduced via immunological mechanisms, just like vaccines. Thus epidemics can be prevented or vastly limited, without the reactionary measure of quarantine. Pending a vaccine, epidemics like COVID-19 can be prevented by increasing the prevalence of precautionary behaviours in the general population via herd immunity, coupled with things like washing your hands frequently and properly, covering your mouth (with your arm, not your hand which then leaves viruses everywhere) when coughing or sneezing and avoiding close contact with those who are already infected. Also Disinfect your mobile device screen twice per day using antibacterial wipes as they generally kill viruses as well as COVID-19 may be able to persist for up to nine days on smooth glass and plastic surfaces, like a mobile phone screen. Avoid touching your mouth, nose, eyes and ears as they are all routes into your body for viruses, and your fingers are constantly in touch with surfaces that may contain viruses. Use a mask as it protects others. Self-quarantine is you are ill or have a fever or feel unwell. Also engage and limit your social network.
Strengthening herd immunity through behaviour is critical to preventing COVID-19 spread. We need to be talking about it more, and doing it more to talk about the low death rates across the population, especially if the vulnerable are quarantined at first. Herd immunity does not convey perfect protection to the individual, or the population, but it stops the spread quickly and economically.