Our vaccination records are bad

Almost three months ago, I noted that the gap between the "partially vaccinated" and "fully vaccinated" numbers in PA were not closing as fast as one would expect them to. For J&J recipients are "fully vaccinated" with the first shot, so no one who gets that shot is counted as "partially vaccinated." For Pfizer, the second dose is supposed to be administered three weeks after the first dose, and for Moderna, the second dose is supposed to be administered four weeks after the first dose. As I noted back in June, if people were following the schedule, one would expect the "partially vaccinated" percentage to be pretty close to the "fully vaccinated" percentage a month later. But that wasn't what happened. Among adults in Pennsylvania, 52.7% were partially vaccinated and 70% were fully vaccinated at the end of May 2021. At the end of June, the partially vaccinated number had moved only up to 54.2%, just a 1.5% increase not the 17.3% increase one would expect if everyone following the vaccination schedule. At that time, I wondered if a lot of people were bowing out after only one shot. I also wondered why there wasn't much coverage of that persistent gap.

It is now months later, and we still have not reached the 70% fully vaxxed rate I would have expected by late June.

Pennsylvania’s daily vaccine update:

12,392,854 vaccines administered
66.8% of PA’ians 18+ fully vaccinated
83.3% of PA’ians 18+ have received at least one dose
National ranking in first doses administered: 9

— Governor Tom Wolf (@GovernorTomWolf) September 10, 2021

At this point I no longer think there over a million¹ Pennsylvanians skipping their second dose of the COVID vaccine. That's just too many people for the phenomenon not to be noticed. Instead I am now convinced that a significant number of people are getting their second dose at a different place from their first dose but forgetting to bring their vaccination card or forgetting to tell the provider they had already received a first shot. So they end up getting counted as "partially vaccinated" twice. Also there are probably people who decided to get themselves a booster (a third shot of Pfizer or Moderna, or a first shot of Pfizer or Moderna on top of J&J) to get extra protection even though the booster is not currently authorized for most people, which means they may lie to the pharmacist giving the shot and their third dose gets counted as a new "partially vaccinated" person.

In other words, the persistent gap between partial and fully is more of an artifact of our decentralized crappy medical record system in the U.S. In other countries with universal healthcare, if someone went to a pharmacy to get a shot they would be found in the national healthcare database, which would be able to accurately tell which dose it is. Here in the U.S., where the shots are free so you don't even need to report it to your insurance company, the injections people get often won't be recorded accurately.

That means that some portion of that 16.5% who is thought to be partially vaccinated but not fully vaccinated probably are fully vaccinated. It also means that some portion of the partially vaccinated number are really double counts of the fully vaccinated numbers, because they represent someone who was fully vaccinated who went to get an unauthorized booster.

But it does mean that the fully vaccinated number is probably an accurate floor of the number of fully vaccinated adults there are in the state. In other words, I think it is accurate to say that at least 66.8% of adult Pennsylvanians are fully vaccinated as of today. We just will never know the real number of fully vaxxed and the partially vaxxed number is probably wrong.

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1-The adult population of PA is 9.63 million. 16.5% (the difference between 83.3% and 66.8% in the Governor's Tweet) of that adult population is 1,59 million people.