One thing I am curious to see but have not yet found are good models or studies which draw connections between declining COVID case counts and the progress of vaccination. For what I assume are obvious reasons I follow the data in New York State most closely. New York’s numbers were coming down quickly early in 2021 but then plateaued and even ticked up somewhat. This was seemingly an interaction between rising vaccination rates, aggressive reopening and the spread of more contagious variants. Over recent weeks those numbers have resumed their rapid decline.
New York State is running ahead of the rest of the country in vaccinations but not by a tremendous amount. The Times says 31% of New Yorkers are fully vaccinated versus 27% of the country at large; 45% to 41% for at least one shot. Remember that these are percentages for the whole population. But almost 20% of the population – those under 16 – are barred from getting vaccinated. The CDC says that 52.6% of Americans 18 or over have already received at least one shot; 35.2% are fully vaccinated.
So, how much of the current decline is tied to the vaccine now that roughly a third of the population is immune (higher if you include the number with natural immunity from getting COVID). We’re certainly not at herd immunity. But as we’ve discussed, it’s not a binary thing, on or off. If COVID can’t get traction with half the population it becomes much harder for it to spread. I have yet to see any modeling of this question. It wouldn’t necessarily be easy. There are many confounding factors: seasonal/climate variation, evolving levels of mitigation, new more contagious variants. Still there’s a lot of data to work with. And it’s not just curiosity. It’s key to planning and likely key to public messaging campaigns to get people vaccinated.
If you’ve seen such modeling or estimates by people with relevant expertise please let me know.
It certainly seems like we have enough data that we should be able to draw some inferences, connections between the rate of vaccination and the rate of spread through communities.