Potpourri -- December 25, 2021

Covid-19: almost no indication of asymptomatic spread, the NFL chief medical officer. It's as good as any "science" Dr Fauci cites. Link here. 

Spanish flu; burned itself out after about four years.

Smallpox: eradicated by herd immunity? USA Today.

Because immunity varies with age and not everyone can get vaccinated — such as those who are immunocompromised, have specific allergies or pregnant women with certain types of vaccines — herd immunity is a crucial protective phenomenon. To establish it, one important factor is the number of immunized people within a population has to be at a certain percentage or threshold. According to the WHO, this figure was eight out of every 10 people for smallpox, based on its early eradication effort.

And because pathogens are not confined by geographical borders, this 80% immunization or higher is not a threshold restricted to one population — it has to be shared by all, whether at a local, national or global level. This means if any populations have vaccination rates below the threshold, there is a great risk for disease transmission to other unvaccinated or vulnerable individuals, even in populations with adequate herd immunity, such as in the case with measles outbreaks in recent years.

For smallpox, this homogeneity in vaccination rates across varying populations was only successfully achieved with mass smallpox vaccination, as claimed by the Facebook post.

A second important determinant for herd immunity is how long biological immunity against a pathogen lasts. While immunological memory forms with every new infectious encounter, this can fade over time, which is why booster shots are typically given. Smallpox immunity unfortunately does decline — after five to 10 years — but it is believed vaccinated individuals still have some protection against fatal outcomes should an outbreak, in the very rare event, reappear.

Routine smallpox vaccination in the U.S. was stopped in 1972, after it was declared eradicated. The CDC only recommends the vaccine to lab workers who work with smallpox or smallpox-like viruses, and to those who need long-term protection like military personnel. 

That's probably as good a summary I've seen in mainstream media. Which raises two questions:

• did the world really get to 80% vaccinated; and,
• if so, how did they ever do it, 80%?

Investing: one of the bigger stories I am watching this next year. COP. Link here. 

Gasoline demand: US gasoline demand the week before Christmas, through Thursday, was up 5.5% from Thanksgiving week and the highest week of 2021.