No briefings so far this week and the case plummet continues, notwithstanding the Delta or Indian scariant. What happens with these variants reminds me of the early weeks of the epidemic, when “front-loading” made outcomes seem far worse than they eventually turned out to be. If you assume in your modeling that the virus random samples the population from the start, that is, that everyone has an equal chance of being infected, you are making a huge and typical statistical error. In fact, in any epidemic, the most susceptible are the most likely to become infected early on and to have worse outcomes. So it is with the variants. When they first get going, they tend to infect the most vulnerable disproportionately, and it may look like they have worse outcomes, but inevitably we learn that they don’t. But as I said last week, terrorists gonna terrorize with whatever they can find.
And here is a piece of research talking about how Delta and P1 are displacing B117 as the most common strain found in the US. (Medrxiv Paper) Big yawn. And, wow, who would have thought this; it is growing faster in counties with lower vaccination rates.
Wuhan, China was the first known epicenter of CV-19 infections. So how long does antibody protection appear to last in those early infectees? According to this paper, one year later those who were infected still had strong antibody responses. While there was somewhat less effectiveness against certain variants in regard to the spike mutations, the antibodies strongly reacted to other segments of the virus and were effective at preventing infection and serious disease. (Medrxiv Paper)
The Pfizer vaccine has probably been given to the most people and appears highly effective. This study compared the antibody effects of vaccination in 871 health care workers with those of natural infection in 181 patients. (Medrxiv Paper) Older vaccinated persons tended to have weaker antibody responses than did younger ones. Females had stronger responses than males. (No word on the other 82 genders.) People who experienced vaccination side effects had a stronger response as well. Among the infected patients those with serious illness had far higher antibody responses than those with mild disease. Vaccination produced stronger antibody responses than did natural infection in almost all cases.
This study attempted to ascertain why some people had higher or lower antibody levels following vaccination. The primary immune system factors leading to higher levels appeared to be more naive (undifferentiated) and transitional B cells and more activation of certain kinds of T cells. (Medrxiv Paper)
Public health experts tend to be more concerned about diagnostic tests that might miss some one who actually has a disease, rather than falsely saying they do. That is a bad attitude that leads to all kinds of costs imposed upon people without the disease. In this research, the authors laud two rapid molecular tests that had a negative predictive value of 99.9% (i.e., basically no false negatives) and were superior to traditional PCR testing. (Medrxiv Paper) The positive predictive value, however, was only 65%, in other words there were a lot of false positives. False positives create a false impression about epidemic spread and have serious consequences, including causing anxiety, among those found falsely positive. Maybe we should be a little more concerned about a test’s ability to be accurate both ways.
Several studies have found that prior immunizations for various diseases, especially viral ones, may provide protection against CV-19. This paper examined the effect of polio vaccination and found a beneficial effect. (Medrxiv Paper)