In the US, Southern states have the lowest vaccination rates, while North Eastern states have the highest vaccination rates. This pattern appears to be largely down to partisanship: Republicans are less likely to be vaccinated than Democrats.
At the end of August, when the Delta variant was dominant, case rates were highest in Southern states like Alabama, Georgia and Florida. Meanwhile, they remained low in North Eastern states like New York, Massachusetts and New Jersey. This is shown in the map below, which gives the official case curve for each state up to 26 December:
The much higher case rates in the South seemed to provide evidence that the vaccines stop infection (in addition to protecting against serious illness and death). Hence, it was believed, vaccine passports will help to curb transmission.
Fast forward three months, and the situation is rather different. Infections are now surging in the North East. This has led to the somewhat peculiar situation whereby case rates are highest in some of the most vaccinated states. See the chart below, based on data from the CDC:
What explains this? One factor is waning effectiveness against infection. A few months after vaccination, you’re not that much less likely to become infected than someone who’s never been vaccinated.
Another factor is regional clustering. Case curves seem to be strongly correlated within regions of the US. This is probably due in part to seasonality. But it could also be due to the simple fact that transmission is more likely to occur between neighbouring states than between ones that are far apart.
A third factor is the spread of Omicron. This mysterious variant has immune escape properties, rendering both the vaccines and natural immunity less protective. And there’s even evidence of negative vaccine effectiveness – i.e., that double-vaccinated people are more likely to catch Omicron than the unvaccinated.
While offering vaccines to the elderly and vulnerable makes sense as a way to achieve focused protection, it’s clear that high vaccination rates in the North East have not curbed transmission. Vaccine passports don’t work in Europe, and they don’t work in America either.