The link to the CSPI article listed a couple of days ago is back up, I strongly commend that article if you are interested in a more creative approach to epidemic dynamics.
Someone said that in regard to the Moronic variant and South Africa, that while the curve looks similar the number of cases is higher. Uhhh, so is the amount of testing–3 1/2 times greater this year than at the same time last year. More testing inevitably leads to more cases. If you assume a constant rate of positivity, actually a lot more cases last year than this year under a steady testing regime. And hospitalizations are not rising in proportion to cases, but at a much slower rate, so once more, it is testing, testing, testing.
It has taken me a couple of days to get this study because it is one that deserves fuller explication. You will recall I have several times said the appropriate analysis for vaccine effectiveness, and infection effectiveness, is to divide the population into four groups–infected but unvaxed, infected (before) and vaxed, uninfected and unvaxed, and uninfected (before) vax. Then you need to track everything by days since the event and you also should be doing your analysis by age brackets. The uninfected and unvaxed are your control group by which everything else gets measured, and your reinfection and breakthrough infection rates are what you use to calculate the effectiveness of immunity derived from prior infection and from vaccination. Your outcomes would include not just cases, but hospitalizations, including days hospitalized and ICU use, and deaths.
This study comes close. (Medrxiv Article) It was conducted in the UK among a large group of health care workers undergoing routine testing to monitor case development. The follow-up period was as long as ten months. Unfortunately the control group was very small as about 97% of the total group ended up being vaccinated. So tthe infected (before) and unvaxed group is also very small. So the analysis was really only comparing two groups, both vaccinated, one with and one without a prior infection. The effectiveness of the vaccines against infection in previously uninfected persons lessened substantially, while it remained relatively high among the group with prior infection, most of whom were subsequently vaccinated. In fact, in this subset of infected-then-vaccinated persons, even 15 months after infection protection was over 90%.
While not highlighted, the authors also found that those persons who had a prior infection but had not yet been vaccinated (measured in the period before vaccination) had fairly similar protection to those with prior infection who were vaccinated. This suggests that vaccination may add little to the protection afforded by prior infection. The researchers also found little difference in protection against infection from a longer interval between vaccine doses, even though that longer interval did appear to result in higher antibody and T cell levels.