Why Is Herd Immunity Suddenly a Good Thing?
In the early days of the pandemic, the idea was prevalent that we should try to achieve herd immunity as soon as possible. It was a terrible, terrible, bad, very bad idea because it meant giving up and letting millions of people die . And yet, now that we have a vaccine, herd immunity is suddenly a good thing. What gives?
In short, herd immunity from vaccination protects people from disease. Herd immunity from natural infection is what you get after failing to protect everyone from disease.
Herd immunity describes how a community protects people.
Let’s talk about what herd immunity really means. This is also called community immunity.
While most people in the community are immune to contagious disease, the few people who are not immune have a lower risk of infection. If, for example, almost everyone in your city is immune to measles – either because of the vaccine or because of being exposed to it as a child – then children who are not yet old enough to receive the MMR vaccine are protected simply because that there are not many people around. to be able to infect them with measles.
Herd immunity is not ideal protection, but it does mean that not many people are affected by this disease, and that these people are unlikely to be in contact with each other. In such a community, it would be very difficult to start an outbreak.
Herd immunity is the goal of vaccination
Vaccinating one person protects that person; vaccinating most people protects vulnerable people throughout the community.
The definition of “most” will depend on how contagious the disease is. At least 92% of people must be immune from measles. With regard to COVID-19, one common estimate is that 70% of people must be immune in order to achieve herd immunity.
In the past, herd immunity held back disease. Smallpox vaccination campaigns have led to the eradication of smallpox on Earth – the only human disease that has ever been completely eradicated. Measles still exists, butoutbreaks in the US are quickly disappearing thanks to our good vaccination coverage and active contact tracing (although the pandemic has thwarted this work).
Infection-mediated herd immunity is not the same
In theory, herd immunity can be achieved through natural infection. But this is not the smartest plan for dealing with a fatal disease for two reasons:
First, if there is no vaccine, we only achieve herd immunity after many, many people get sick. If you had a community where 70% of people survived COVID-19, that would mean that the community would have buried many of its residents, and many of those who remained would have long-term complications. (Not to mention the collateral damage to an overburdened healthcare system and the economic fallout from an uncontrolled pandemic that would have resulted in more death and more suffering.) Even if the remaining 30% were protected, it was terribly expensive.
Second, if the only way to gain immunity is to become infected yourself, it is impossible to provide this immunity to newcomers – for example, infants – without exposing them to all the dangers of illness. Herd immunity without vaccination is temporary.
The reason vaccines are so valuable is because they give us immunity without forcing us to go through all the danger of disease. Herd immunity from natural infection is the result of tragedy, and vaccines allow us to safely achieve herd immunity.