The NC Threat-Free Index and Immunity Update for the Week Ending January 10

Image source: Screenshot from a Youtube video posted Jan. 8 featuring happy crowds enjoying the NC Chinese Lantern Festival at Koka Booth Amphitheatre in Cary, which does not require masks of its patrons, stating that “As always, all patrons and guests have the right to make choices that work for themselves and their families.”

This past week 97.7% of people in NC were estimated to pose no threat of passing along COVID-19 to anyone. That is the lowest estimate recorded by this index, dropping below estimates from this time last year, which is in the height of cold and flu (respiratory viruses) season. Nevertheless, about 13 out of 14 (92.7%) adult North Carolinians are estimated to have either vaccine-induced or natural immunity.

A note about that immunity estimate: In keeping with the shifting definitions of “vaccine” and “vaccination” from the Centers for Disease Control and Prevention (see discussion here), the Associated Press recently filed a story explaining “Why are so many vaccinated people getting COVID-19 lately?” The AP wrote that “People might mistakenly think the COVID-19 vaccines will completely block infection, but the shots are mainly designed to prevent severe illness.” 

Shame on you for mistakenly thinking such a thing. Further shame on you if you are in the possession of a memory that the CDC’s longstanding definition of a vaccine used to include “A product that stimulates a person’s immune system to produce immunity to a specific disease, protecting the person from that disease.” Only very recently did the CDC “correct” its definition of a vaccine to “A preparation that is used to stimulate the body’s immune response against diseases,” removing the part that added “to produce immunity to a specific disease, protecting the person from that disease.”

The Threat-Free Index’s discussion of vaccine-induced immunity is based on the proportion of North Carolinians who have received a Covid-19 vaccine, which is unfortunately an inescapable limitation of estimating who has (old definitional) immunity from Covid-19.

With respect to naturally acquired immunity from prior infection, there are as of this date 146 research studies attesting to the strength of natural immunity, even in comparison with vaccine-induced immunity.

Here is the NC Threat-Free Index for the week ending January 10. All of the statistics generated for the NC Threat-Free Index are based on numbers provided by government sources. This link gives a detailed explanation of how each statistic is derived.

• As of January 10, there were 1,620,648 North Carolinians presumed to be recovered from Covid-19.
• Active cases comprised 13.1% of NC’s total case count. A case of Covid-19 isn’t a permanent infection. Only someone with an active case of the virus can conceivably transmit it to you. The total case count given banner headlines comprises active cases, the very large proportion of people who have recovered, and the very small proportion of people who have died with Covid-19.
• Active cases represented 2.3% of NC’s population. Active cases are lab-confirmed cases of Covid-19 minus recoveries and deaths.
• Also, about 6 out of every 7 (85.9%) of NC’s total cases were recovered. People who have recovered from Covid-19 are no longer infectious. More importantly, a large and growing body of empirical research (“science and data”) shows that they have acquired persistent, long-lasting, and robust natural immunity to Covid-19 — immunity that is stronger against Covid-19 and its variants than even that enjoyed by those who are fully vaccinated.
• Only 0.18% of people in NC had died with Covid-19. This statistic must be phrased in that manner (“with,” not “from”) because of the lack of clarity over the actual cause of death and because of the research finding as well as DHHS and the CDC admitting that a significant proportion of COVID-19 hospitalizations and deaths were “not related to Covid-19.” A recent investigative report found that 1 in 3 Covid patients at UNC Health and a whopping 60% of Covid patients at WakeMed had gone to the hospital for non-Covid reasons.
• All things considered, 97.7% of people in NC posed no threat of passing along Covid-19 to anyone. This estimate will fluctuate based on relative growth in lab-confirmed cases vs. recoveries.

Herd immunity, reinfections, and post-vaccination infections

For the week ending January 10:

• Now about 13 out of 14 (92.7%) adult North Carolinians are estimated to have some immunity, whether vaccine-induced immunity or natural immunity, the stronger and more durable immunity, to Covid-19. Adults are the ones most at risk of losing their jobs, access to government services, ability to travel, ability to buy groceries, etc., for not being vaccinated even though the ostensible public interest is in immunity. 
• Conversely, as of January 10, only about one in 14 (7.3%) adult North Carolinians were estimated to have neither vaccine-induced nor natural immunity.
• Looking at the total population, almost eight out of nine (88.3%) North Carolinians are estimated to have some immunity. These estimates are based on DHHS case numbers, CDC estimates of actual infections, DHHS estimates of current vaccinations, and the formula outlined here.
• After pointing out again last week the wide discrepancies in the official counts of fully vaccinated individuals given by DHHS (from 5,567,698 for November 6 down to 5,302,535 for December 11), the latest update added over half a million fully vaccinated individuals to the count from December 11–25. It is now 5,838,242.
• The most recent update from DHHS found 135,956 post-vaccination infections, which would put the estimated post-vaccination infection rate for the week ending December 27 at 2.3%. Given how strictly DHHS defines a “post-vaccination infection” — as of now, someone must be at least two weeks past receiving the second of two injections; anyone with only one injection or within two weeks of receiving the second “counts” as an unvaccinated case of Covid — the actual post-vaccination infection rate could be much higher than the estimated rate.
• Also as of the week ending December 27, 28% of Covid-19 cases in North Carolina were to people considered fully vaccinated.
• As of the week ending December 27, there had been 23,463 reinfections for those with prior lab-confirmed cases of Covid-19, and the estimated reinfection rate was 1.4%. For reasons discussed here, the actual reinfection rate is likely much lower than the estimated rate. 

DHHS discovers another “new” case from a year ago

Sometime in the past week, DHHS reported as a “new” case one that was found back on January 3, 2021. Also, DHHS continues to amend its daily counts of reinfections back to the beginning of October (when it started tracking reinfections daily). 

I find it surprising that those data are still changeable several months after the fact, except for the reality that it is perfectly consistent with how DHHS has treated data from the very beginning. As the COVID Tracking Project finally had to warn: “Interpret North Carolina’s historic data with caution.”