Covid-19 Vaccines Have Declined in Relative Efficacy in Los Angeles County in Terms of Both Transmission and Death Rates Although Death Rates Themselves Have Declined

May 19, 2022 - Covid-19 vaccines were relatively more efficacious in preventing transmission and death seven months ago than they are today although they were never very effective at preventing transmission of disease.

Using publicly available data from the Los Angeles County Department of Public Health it is possible to compare how the vaccines performed over the summer, when they were first widely available to how they have performed this past winter.

Over the span of time between June 1, 2021 and September 30, 2021, there were:

140,789 Covid-19 cases total

53,908 vaccinated cases (38.3% of the total)

86,881 unvaccinated cases (61.7% of the total

1,760 deaths total

239 vaccinated deaths

1,521 unvaccinated deaths

4,907,895 average population of vaccinated individuals (49% of the total)

It is impossible to discuss hospitalizations, as the county counts hospitalizations for other conditions as a Covid hospitalization if the patient happens to test positive for the disease while in the hospital. The patient does not necessarily have to be in the hospital due to Covid symptoms. Therefore, it is not possible to track the vaccine's effectiveness at preventing hospitalization - or at least not from publicly available data.

Over a similarly-lengthed span of time between January 18 and May 16, 2022, there were:

604,126 Covid-19 cases total

362,205 vaccinated cases (60% of the total)

241,921 unvaccinated cases (40% of the total)

3,915 deaths total

1,541 vaccinated deaths

7,181,247 average population of vaccinated individuals (71.7% of the total)

The benefit the vaccine provides to prevent transmission dropped drastically between the summer span of time, when the Delta variant was dominant, and the winter span of time, when various versions of the Omicron variant has been dominant. During the summer span, 1.1% of the vaccinated population caught Covid. During the winter span, 5% of the vaccinated population caught Covid. The vaccine's effectiveness at preventing transmission reduced nearly five-fold.

The crude case fatality rate of the vaccinated (number of vaccinated deaths per vaccinated infections) did improve somewhat between the summer and the winter, but that appears to be due solely to the difference between the the Delta and Omicron mutations of the virus, because the crude case fatality rate of the unvaccinated improved even more.

To show this, look at the crude CFR of the vaccinated over the summer, which was .443%. Over the winter, the crude CFR of the vaccinated was .425%. The improvement was .018%.

Meanwhile, the crude CFR of the unvaccinated over the summer was 1.75%. Over the winter span, this improved to .98%. The improvement was far more for this group, .77%.

The fact that the unvaccinated are enjoying an increasingly lower case fatality rate while the vaccinated are not enoying as large an increase in improvement indicates powerfully that the vaccine is providing less of the protection against death than is the increasing mildness of the virus's mutations.