Making Shit Up: CDC Had No Basis For New Guidelines

Hard to believe a public health agency is running a campaign to drive vaccination by scaring people about cost of seeking care. Is CDC unaware of gaps in our healthcare system that already leave many vulnerable Americans excessively exposed to the costs and consequences of Covid? https://t.co/iEmPxYP1uO

— Scott Gottlieb, MD (@ScottGottliebMD) December 27, 2021

erictopol  |  There were serious problems about the new 5-day isolation period. First, there are no data or evidence to back it up. Yes, we’re facing an Omicron onslaught of cases and it would be useful to come up with a strategy to avoid a mass loss of functionality among our workforce and the on-the-go public, no less in the midst of the holiday season. But that doesn’t justify issuing a vacuous guideline. Second, there was no mention of using a test, to confirm that the isolated individual is now OK to circulate, that there is no indication of infectiousness. That could be done via a rapid antigen test, which denotes infectiousness, carries some reduced sensitivity with Omicron, or via a PCR. The cycle threshold value of a PCR test is also indicative of infectiousness; the lower it is, the more likely potential for spread. Either of these tests would be far better than no test to justify a reduced isolation time in any individual.

Third, there are no data for Omicron’s clearance time. We know the characteristics of shedding and average time it takes for clearance of the virus for Delta and preceding variants, but to date we have not seen any such data for Omicron kinetics. With the Hong Kong report of 70-fold copies of the virus in the upper airway for Omicron versus Delta and prior variants, there is no certainty yet that Omicron’s clearance is fast.

Fourth, the guidance did not mention a word about vaccinated or unvaccinated status of people. We know from past studies there is a more rapid clearance among vaccinees than people who were not vaccinated, but the recommendation does not take this knowledge into account. Fifth, it assumes that all people handle the virus similarly when, it fact, there is considerable variability.

Note from the Figure that there are significant differences for vaccinated, average 5.5 days (95% CI 4.6, 6.5), compared with unvaccinated, average 7.5 days (95% CI 6.8,8,2) There is marked inter-individual variability: for example, look at all the green dots even >20 days in the unvaccinated group, panel D. These data, representing nearly 20,000 samples, were obtained from predominantly healthy young men and may not be representative of the population at large. By the way, the NBA uses a 6-day isolation cutoff with testing with heavy emphasis on testing.

This problem can be fixed. The CDC could come out and revise their guidance and say there are no such data for Omicron (as a cover, like they did when they finally recommend boosters for all adults) and require testing. Even the airlines, which pushed for a shortened 5-day isolation period, wanted to use testing as part of that requested change in policy.

But the bad day wasn’t just about isolation in isolation. There was also the major gaffe about genomic sequencing surveillance. Here are the data from last week, and the corrected data this week, announced today by CDC. The point estimate for Omicron changed for the week ending December 18th from 73% to 22.5%, which is remarkable. We were led to believe that the country was well in the midst of the Omicron wave when, in fact, we were and are still experiencing a large number of Delta infections. As of December 25th, the point estimate is 59% with 95% confidence intervals lower 42%, upper 74%, indicating there is a lot of wobble, a relatively limited number of sequencing samples to draw upon, no less a reduction in confidence for the CDC itself.