I am not particularly interested in the cause ... but, the Bayesian in me combines the fact that CDC stopped reporting number of breakthrough infections combined with the facts that chances of dying from Covid19 are low to being with and supposedly lowered by the vaccine gives me the gut feeling that breakthrough infection rates are now probably around 2-3% which means there are a whole lot of typhoid Marys walking around with high viral loads.
> Among 1497 fully vaccinated health care workers for whom RT-PCR data were available, 39 SARS-CoV-2 breakthrough infections were documented. Neutralizing antibody titers in case patients during the peri-infection period were lower than those in matched uninfected controls ...
For the record, that's 2.6% breakthrough infection among fully vaccinated people who are healthier and more careful than the general population.
Right - the only logical variable to account for the increase would be Delta. Unless you're implying some other cause for the increase?