A Current Vaccine Efficacy Estimate: 1/7th Risk of a Detected Infection

Can we approximately estimate a current measure of vaccine efficacy from basic recently reported data??Fully vaccinated people make up quarter of new COVID-19 infections in Los Angeles County (yahoo.com) ?The article indicated that there were a total of 13,598 infections from July 1 to July 16 and 3592 of these infections were in vaccinated people.?Other available LA County data indicates 70.7% have had one or more doses of vaccine (62% are fully vaccinated).?We can back out relative risk of infection for the vaccinated by using the vaccine rate data in conjunction with one additional assumption.?The vaccinated and unvaccinated have similar exposure to Covid.?The vaccinated, in LA County, have about 1/7th the chance of acquiring a case of Covid that is detected as compared to the unvaccinated.?Many recent infections in LA County are the delta variant which can be taken to infer that there is still much benefit to vaccination even in the presence of the delta variant of Covid.??

Caveats:?This is an approximate analysis and set of perceptions, caveat emptor. ?Data analysts tell stories about the meaning of data, better stories mostly survive the test of time and expert review.??