Update: Miami-Dade County vaccination rate even lower than I thought

Last September I wrote about something which had been bothering me for awhile:

HOWEVER, there's one major outlier over the 65% threshold...Miami-Dade County.

According to the Centers for Disease Control, Miami-Dade has fully vaccinated 68% of their entire population (1.84 million out of 2.72 million residents). I use the slightly lower official 2020 U.S. Census popualtion count for Miami-Dade County (2,701,767), which makes the vaccination rate slightly higher still: 68.24%.

And yet, somehow the 10th-largest county in the United States, which has the 6th highest vaccination rate of any county over 1 million residents, also has the highest new case rate of any county over 1 million residents.

At the time, it was Miami-Dade's massive outlier status in terms of COVID cases since the beginning of July which had tipped me off; it looked like this:

After putting this out as an open question to anyone from Florida who had some insight, a two common themes kept coming as reasions for the discrepancy:

...the most common thinking is that it's a combination of lots of snowbirds (seniors who live up north and only spend the winter in Miami-Dade) who got vaccinated in M-D back in January/February before flying back up north for the rest of the year) and "Medical Tourism"...i.e., folks from other countries flying into M-D, getting vaccinated and then flying back to their home country.

In March, Palm Beach Post reporter Chris Persaud (w/help from David Berman) published an in-depth analysis of Florida's questionable vaccination rate data and sure enough...

Florida overcounts vaccinations by 600,000 people. Snowbirds responsible, analysis shows.

  • Health officials and Gov. Ron DeSantis say they have no plan to fix this statistical flaw, driven by out-of-staters.

...More than 100 Florida ZIP codes each report that more than 100% of their residents have gotten at least one coronavirus vaccine shot. In some cases, the number of vaccine recipients recorded by the state Health Department exceeded U.S. Census population estimates by more than 1,000%.

These ZIP codes — popular among seasonal residents and tourists — together counted about 622,000 more inoculations than people living there year-round.

That comprises 4% of vaccine recipients tracked by a database state health officials gave on Wednesday to lawyers representing a consortium of news outlets, including The Palm Beach Post.

About 74% of eligible "residents" ages 5 and older are at least partially inoculated, state health officials reported March 11. And about 24% have received a booster shot. The overcounted inoculations are equivalent to about 3% of vaccine-eligible Floridians.

...Florida's official data also underestimates how many residents have never been vaccinated, Salemi said.

...Florida reported a total of more than 5.8 million infections and 71,860 deaths as of March 11. But those numbers exclude tourists, snowbirds and other visitors who caught the virus here.

...Nearly 2.3 million immunized people across Florida listed their residences in ZIP codes with impossible vaccination rates, according to the state Health Department database.

But fewer than 1.7 million vaccine-eligible people live in these places for more than half the year, Census surveys conducted from 2016 to 2020 found. ZIP code-level estimates for 2021 are not yet publicly available.

Florida’s growth since 2020 does not fully explain the six-figure discrepancy between immunizations and estimated population in ZIP codes analyzed. Much of it is driven by out-of-state residents who stay here during winter.

...Much of the impossible immunization rates in Miami-Dade County can be explained by “international people who give a local address just to get the vaccine,” Alonso said. “We have vaccinated almost all of Colombia. That's one of the jokes.”

The full 100+ Florida zip codes noted in the Palm Beach Post weren't easily available (you had to roll over each individual zip code on the interactive map), but I managed to match up 23 of them within Miami-Dade County which contained over 331,000 of the ~622,000 "phantom resident" vaccinations referred to, or over 53% of the total state-wide.

My conclusion at the time was that the actual 2-dose vaccination rate of residents of Miami-Dade County was at least 331,000 fewer than the official tally for the county...or just 72.4% as of late March 2022, as opposed to the official vaccination rate of 84.7%.

Recently, Mr. Persaud kindly forwarded me the raw data used in the March article, which includes all 102 of the zip codes in question (as well as the other 850+ zip codes in Florida). It turns out I had missed 4 more Miami-Dade County zip codes in which the official vaccination rate as of late March was over 100% of the total over-5 yr old population.

In other words, instead of M-D County's late March vaccination rate being overstated by 331,000, it was actually more than 428,000 people...or nearly 69% of the total "phantom resident" vaccinations statewide.

In actuality, the total number at the time was likely considerably higher than 622,000...those are just the ones which surpassed 100% of the resident populations of those zip codes. There are likely several hundred thousand more in zip codes where the official count is, say, 98% when it should actually be 75% or whatever...but there's no way of being certain about those.

When updated as of June 8, this means that in Miami-Dade County, at least, the actual 2-dose vaccination total is only around 1.90 million residents (70.4% of the total population) at most instead of the official count of 2.33 million (86.2%). That's a drop of 15.8 points.

Assuming the actual vaccination rate for M-D is ~70.4%, it would be where the big black circle below is: