There’s a built-in fallacy to herd immunity that shows the difference between a mathematical model where there’s an assumption of even distribution and the practical world where samples are heavily clustered. It’s also not a stable temporal model when that immunity is perishable with a half-life of around 6 months.
I think herd immunity was presented as a target to encourage optimism and participation but I think the lazy, the “vaccine hesitant” and the “my freedumbs!” crowd have used it as an excuse not to be responsible for their own health choices because others will make the waters safer for them. It really doesn’t work that way.
As we can see from our own country, and especially in foreign countries which are more vaccinated than the US, COVID still exists in regions which are heavily vaccinated because contagion is fluid. It’s like peeing in a swimming pool. Vaccination works on a micro level. The numbers unarguably prove that it does. But it’s a fragile stasis because geographical immunity is like boxes within boxes within boxes. People, particularly those with no immunity, don’t stay in their home boxes.
My Brooklyn zip code is reported by NYC DOH to be 90.78% fully vaccinated. That’s higher than the citywide median of 69.9%. but we still had a COVID positivity rate this past week of 1.58% by those who got tested. That’s because immunity is leaky in Box #1 when the citywide vaccination rate (Box #2) is 29% lower, the state rate (Box #3) is slightly lower than that and the national rate (Box #4) is significantly lower: 59% as of this week.
I think we need to abandon the herd immunity model because it’s only going to disappoint those who expect that COVID will miraculously disappear once the country reaches 70%, 80%, 85%, etc immunity. The disease will easily bide its time, waiting for its next victim, including those with waning immunity.
I believe the future of this endemic — because it’s really not a pandemic anymore — is that there are those who will get their annual or biannual COVID shots along with their flu vaccines and, barring a breakthrough variant, they’ll be 99.999% safe from infection and serious illness. The rest of the public will still be up for grabs by the pathogen. The deadly bug will continue to claim victims from its ranks, especially every fall and winter. The writing’s already on the wall to prove that when 99% of the people dying in COVID wards now are unvaccinated or lacking in disease-acquired immunity.
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