Why are Infections on the Rise Again? (Part 2, Beyond Arizona)
About three weeks ago, I noted that infection rates were going up in the UK. It has a history of leading pandemic trends in the U.S. by a couple of weeks. Sure enough, now cases are rising all over the U.S. The same thing is happening all over Europe.
On Saturday I blogged about the huge numbers of people in Arizona who are unvaccinated and previously uninfected as a way of explaining how we could still be seeing such high infection rates. But what about other states where they have higher vaccination rates?
Vermont has the third-highest vaccination rate in the country, at 71.87%. Yet they are experiencing a new surge of cases.
The estimated Vermont population is 623,251. That's 8% of the population of Arizona, so it's important to adjust for that if we are going to compare them.
The infection rate for Arizona is 46.47 cases per 100K people (based on a 7-day average). The same figure for Vermont is 54.71. How can this be when they have such a high vaccination rate, essentially 20% higher than Arizona? The answer is they haven't had as many infections.
Here are the same estimates I did for Arizona on Friday, applied to Vermont. The covidestim.org site estimates that 37.59% of Vermonters have been infected (versus 75% of Arizonans). That's means 388,971 of them have not been infected. If we assume vaccinated and unvaccinated people are distributed according to population rates, that means 109,417 Vermonters are both uninfected and unvaccinated.
That's about 17% of their population, not that different from the approximately 11% of the Arizona population that is uninfected and unvaccinated. In both cases, there are plenty of people for the virus to get.
Questionable Assumption
But as noted on Friday, that kind of statement depends on a questionable assumption—that the only people who can still be infected are people who are not previously infected and haven't been vaccinated. We know that is not the case.
Vaccines protect against infection and serious disease but "breakthrough" cases do occur. In September the CDC estimated they happen at about 1/6th the rate of infection in unvaccinated people.
New research also shows that Pfizer vaccine quickly begins losing effectiveness. People are 1.3 to 1.7 times as likely (depending on age group) to be infected two months after their second dose as they are right after their second dose (as noted in a Part 1, Arizona relied heavily on Pfizer in its early rollout; I don't know about Vermont).
So vaccinated does not equal "ineligible to be infected." Neither does previously infected but unvaccinated. A study in the UK among medical workers done before vaccine was available showed that a previous infection was only 83% effective at preventing re-infection. That number may be even lower now that we have Delta.
So the possibilities of breakthroughs and re-infections mean there are even more more people available to be infected than my estimates suggest.
It Ain't Over
No matter how much we might wish otherwise, the pandemic is not over. Frustratingly, we are probably looking at a fifth wave.
As Andy Slavitt (departing White House pandemic advisor) noted in a recent tweetstorm, we need to stop thinking it's over. That kind of mindset encourages people to let their guard down.
Instead we need to double-down on efforts to curtail spread of the virus. That means getting vaccinated, getting boosters, and wearing masks indoors, especially in crowded places.
Image by Peggy Marco from Pixabay
