A comparison of how we talked about herd immunity in 2019 versus 2020

Last year there was a measles outbreak in New York. It got a lot of coverage and I followed closely. There was a lot of talk about herd immunity then. I want to show you how the conversation compares:

2019

Vox:

That’s what’s known as “herd immunity,” and it means diseases can’t spread through populations very easily.

Wired:

protect the most vulnerable people in communities through a process called herd immunity. If enough people are immunized, there simply aren’t enough susceptible individuals for a virus to spread easily throughout a group. The virus runs out of steam ramming the doors of impenetrable fortresses before it can reach those who are too young to be vaccinated or whose immune systems are weak.

New York Times

Herd Immunity: For an outbreak to end quickly, each infected person must infect, on average, fewer than one other person. In this example, at least 17 of every 18 people (more than 94 percent) would need immunity. This threshold is sometimes called the herd immunity threshold.

2020

The Daily Beast

White House advisers have embraced the controversial belief that herd immunity will help control the COVID-19 outbreak, according to three senior health officials working with the White House coronavirus task force. More worrisome for those officials: they have begun taking steps to turn the concept into policy.

New York Times

A manifesto urging reliance on “herd immunity” without lockdowns was warmly received by administration officials. But the strategy cannot stem the pandemic, many experts say.

NBC News

Covid-19 herd immunity, backed by White House, is a ‘dangerous fallacy,’ scientists warn

BBC

WHO head calls herd immunity approach ‘immoral’ The head of the World Health Organization has ruled out a herd immunity response to the pandemic.

________________________________

So what gives?

The difference between 2019 and 2020 is that last year, they talked about herd immunity reached by vaccination. This year, they are talking about natural herd immunity. Herd immunity in itself is not something anyone is disputing. The media is misrepresenting it.

There is a lot of confusion about herd immunity because the coverage of it has been so polarized. Herd immunity is not some magic thing that makes a virus die out forever. Herd immunity is not a button or a moment. It’s a concept that explains how the benefits of our collective provide extra help (besides for the work of our immune systems) in dealing with outbreaks.

Sunetra Gupta gave some great explanations on herd immunity in this interview in July:

It [Herd immunity] is just a technical term. It’s just a technical term for the proportion of the population that needs to be immune in order to prevent the disease from spreading, which is the central concept in vaccinations. It’s a fundamental epidemiological concept, which clearly has been subverted. I guess the fact it includes the word herd has made it easier.

So, there’s the herd immunity threshold, which is the point at which enough people are immune to a pathogen that the rate of growth will start to decline. But there will still be more cases. Typically in an epidemic, we overshoot that threshold. So if you see an area that has a seroprevalence with 60%, that doesn’t mean that herd immunity can’t be much lower than that. What that threshold does define for us is how many people in the community you need to be immune for that thing not to take off.

Flu is clearly a very dangerous virus, but the reason we don’t see more deaths from flu every year is because, through herd immunity, the levels of infection are kept to as low a level as we can get.

Finally, Gupta predicted it will come back in some form:

I suspect that in the winter it will probably come back, but hopefully only to the regions where it was kept from going by lockdown, and where the seroprevalence levels are genuinely extremely low.

We can be cautiously hopeful that in areas where the seroprevalence levels have achieved a certain value that’s compatible with there being a proportion who are resistant, that it might not come back with such vehemence.

_______________________________

It is typical of our time that a solid epidemiological concept should become a superficial meme.

submitted by /u/friedavizel
[link] [comments]

Leave a Reply

Your email address will not be published.