(CNN) Local officials sound the alarm over another possible wave of Covid-19 infections. Quoting,

In Arkansas, which has one of the lowest vaccination rates in the nation, cases are surging, officials said…”The vaccine, as well as continued practicing of social distancing and masking when that is necessary, are our pathways out of a third surge of Covid-19,” Patterson said.

The advice of Dr. Cam Patterson leaves “when that is necessary” undefined. A prediction of vaccine breakthrough percentages, which might help decide, is given in Delta Strain of COVID — We’re in for a Rough Ride; Napkin Calculation #3,  and validated in The Royal Pharmaceutical Society; Delta Strain of COVID; Napkin Calculation #3.  Quoting,

A breakthrough infection percentage of between 5X and 10X the percentage of hospitalized patients, breakthrough of 20%-40%. compared to 5% for the viruses of the original Phase 3 study.

This is not contradictory to the established effectiveness of vaccines. Yet it allows the possibility that in Arkansas, and even in locales with borderline vaccine uptake, such as LA, community infectivity may overwhelm the protection of the vaccine.

Though vaccines are a great boon to the individual, experience with Delta is lacking in communities with high levels of vaccination, which may experience community levels of infectivity well above background. Discretion is the better part of  valor.

I’m putting my mask back on. You are invited to do likewise.