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Comment by joshuahedlund | Hacker News Reader

Counterpoint is Madrid, Spain, which had one of the worst outbreaks in the spring (antibody tests showed prevalence of 11%[0], higher than Stockholm[1]) and now is having a severe outbreak again[2]. What explanation is there other than herd immunity not having been reached?

As for Sweden, there's a lot of variety in human behavior and a lot we don't understand about the virus, and there are many possible explanations for the lack of major spread in any particular area. Sweden has continued to post a steady low level of cases over the last two months, not a continuing bell-curve decline, suggesting the virus is still consistently finding new hosts, just at a low and steady pace.

[0] https://www.reuters.com/article/us-health-coronavirus-spain-...

[1] https://www.theguardian.com/world/2020/may/21/just-7-per-cen...

[2] https://medicalxpress.com/news/2020-09-doctors-hard-hit-madr...

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The number you're citing for Stockholm is from April, well before the outbreak became severe in Sweden. Cases in Sweden continued to grow after that, and didn't peak until late June, when daily case counts were 3x higher than in April. (Although it's important to point out differences in testing - the positivity rate peaked April 20th - 26th).

That's a different experience than Madrid, where the virus hit much earlier. By the end of April, daily case counts were 1/5th of their peak in Madrid.

I'm not aware of a more recent study.

Please, please, stop reading and sharing hysterical news reports and go right to the data.

Here's daily deaths in Spain:

https://i.imgur.com/G84d20p.png

All numbers about total reported cases from the spring are going to be way, way off. There simply wasn't enough testing.

Deaths do not lie, which is why we should focus on those numbers. And by those numbers, this is in no way a repeat of Spring for Spain.

It's not a repeat of the spring...yet.

The daily number of cases in Spain appears to still be on the rise, and the death curve is usually 3-4 weeks lagging the cases. So deaths is likely still on the rise.

All that said, it may not reach the same proportions as the spring. But it is too early to wave it off either.

> Counterpoint is Madrid, Spain, which had one of the worst outbreaks in the spring (antibody tests showed prevalence of 11%[0], higher than Stockholm[1]) and now is having a severe outbreak again[2]. What explanation is there other than herd immunity not having been reached?

The outbreak in Spain isn't as severe as you might think, there's a lot more positive tests, yet a lot less illness.

Herd immunity just means that R=1 without precautions. I would agree that Spain hasn't quite achieved herd immunity, but spread right now isn't anything like earlier this year.

One could speculate that because Spain went into such a strict lockdown, herd immunity could not be achieved, or that herd immunity was achieved, it just didn't last because COVID immunity doesn't last.

Antibody testing is getting tricky now, because antibodies are starting to fade, so unfortunately seroprevalence numbers will become underestimates with time.

That being said, in one hard-hit area of Stockholm, seroprevalence was 19% (https://www.folkhalsomyndigheten.se/publicerat-material/publ...). Stockholm as a whole has about 11% seroprevalence in their most recent numbers, but again, I believe antibodies are starting to fade now (https://www.folkhalsomyndigheten.se/publicerat-material/publ...).

I'm afraid I don't follow.

Sweden didn't lock down because they wanted to achieve herd immunity quickly, while still taking measures to protect the most vulnerable. Spain locked down, actively attempting to minimize the spread of the virus.

How is the failure of Spain to achieve herd immunity (while actively attempting to achieve the opposite) a counterpoint to the Swedish example?

> Sweden didn't lock down because they wanted to achieve herd immunity quickly

This is a popular myth. There are no such statements (no not even from internal communication and similar). It was never a “strategy”

"In August, emails between the two men from as early as March show how they discussed herd immunity to limit the spread of the virus in Sweden." - Newsweek: Sweden's 'Herd Immunity' Mastermind Gets Promoted by WHO

https://www.newsweek.com/sweden-herd-immunity-mastermind-who...

One email thread out of thousands released where they brainstorm theories and predictions. Doesn't mean it's the official strategy and Giesecke is not even employed by FHM but retired.

These were exactly the emails I mean. Anyone who reads them can clearly see there is not even a slight suggestion that reaching herd immunity is somehow a possible “strategy”.

The simplest explanation for Madrid is that it locked down too early, and herd immunity (which seems to occur at about 20-25%, based on Antibody testing of New York and Sweden) was never reached.

Lockdown also seems to increase the threshold for herd immunity and increase deaths, by dramatically changing the demographics of who is infected. Without lockdown, the youngest and most mobile people are likely to be infected - with minimal/zero deaths since COVID mortality is incredibly age dependent.

Under lockdown, those people are at home and intermingling with family. The only 'social' activity is shopping for food, leading to an unnatural mingling of old and young.

I live in Ukraine which has masks and little else against COVID. In shopping centers particularly in the evenings there are essentially zero old people - they fear for their lives, as they should.

The most effective policy we could have adopted was 6AM-10AM public transport and shopping for the aged only, and everyone else from then on. Segregate the elderly population into the mornings and let the masses in in the afternoon. This might have required shifting school and work to later hours in the day for three months, which seems a minor inconvenience.

Nobody credible believes 20-25% is a likely threshold for herd immunity. You cannot Realistically in America isolate the old from the young and if the young spread it like wildfire the old get sick.

Literally everything in your post is as poorly considered. It's important not to spread misinformation.

It's 20%-25% of currently detectable antibodies, coupled with another 20%-50% from prior coronaviruses or other cross-immunity. That's the important distinction. The sum approaches the 50%-70% needed for herd resistance based on 1-1/R0. That's the point of this article.

A couple people suppose is not the same as proof

See: https://www.news-medical.net/news/20200731/Research-suggests...

In addition to immunity based on T cells, the HIT depends on how individuals are networked. The original 60-70% estimates were based on 100% of people being vulnerable and also a random distribution of individuals interacting. In reality a small fraction of the population will have many interactions and once they become immune those transmission vectors away and the average R number drops. So based on the latest research plus observations of the worst hit places, 20-25% seems plausible.

Why are you assuming young people don't live with old people? It's extremely common.

It's rather uncommon in most European countries:

https://ec.europa.eu/eurostat/documents/3433488/5579620/KS-S...

Looking at this data for the US, it could be a factor for COVID mortality being higher in minorities:

https://www.pewsocialtrends.org/2010/03/18/the-return-of-the...

Your data actually says the opposite for Europe - it's highly dependent of the country of course, but if you look at page 6, in Southern countries - Spain, Italy, you have >30% of old people living with larger family (columns 'living with partners plus others' and 'no partner, not living alone'). That comes out at <10% for Nordic countries (Finland, Sweden etc)

Three-generation house-holds or households where adult children live with their older parents are very uncommon in most, but not all, EU countries.

The numbers you cite are explained by old people living in retirement facilities or coliving arrangements, but that doesn't imply cohabitation with young people. Under these circumstances, special precautions can and must be taken.

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