CDC realizes the vaccinated can spread covid 19 delta variant-now what

 CDC has now seemingly realized that fully vaccinated people can harbor large amounts of the delta variant in their noses and are able to transmit the disease to others. This is a conclusion that could have been reached upon analysis of the Houston Wedding event in which 6 fully vaccinated attendees develop covid  although admittedly there are alternative  less likely explanations for the Houston wedding cases.

In May 2021  when CDC seemed to set people free from mask use the data it had indicated that the likelihood of spread  from the fully vaccinated was low enough to recommend that masks were no longer necessary for vaccinated people under many circumstances.

But by July 29 with access to new data CDC concluded  that fully vaccinated people could  actually spread the disease and that the data they relied on for that conclusion would soon be released. That data is now available Further the greater infectivity of the Delta virus prompted CDC to express a much greater concern.

It now seems that the following should be considered the  operational reality on the ground.

1. Fully Vaccinated people can develop and spread covid 19 delta variant.In the vast majority of cases the disease is either mild or asymptomatic.

2.Some very small  percentage of fully vaccinated people can develop serious and fatal covid 19

3.Delta variant infection results in significantly higher viral loads and infectivity and possibly 

more serious disease. (data from Canada ,Singapore and Scotland  show Odds Ratio for ICU admission range from 3.87 to 4.9 ) 

4.Large areas of the US have relatively low levels of full vaccination 

So practically what does all of this mean.

If you are vaccinated you still  may need to wear a mask.

Why?

Since fully vaccinated people can spread covid wearing a mask protects others. There are two sets of others, the vaccinated and the unvaccinated.  A vaccinated person can contract covid and bring it home to infect children and the elderly. 

If you are not vaccinated you need to wear a mask.Masks should be N95s and ideally covered by a blue procedure or surgical mask.After exposure the mask could  be stored in a container so that they can be used after a several days period of "decontamination "  Adding a face shield to the mask may add another layer of protection although strong supporting data to that point seems not to exist The double mask has not been recommended this time by the CDC but that was recommended for a surge from a Covid version that was less contagious and perhaps less lethal than the delta strain.. Now the CDC advises that the vaccinated should wear masks if they live in a area with a high test positivity rate and a low rate of vaccination.

5.At least some of the geographic  areas cited in item 4 have governors and/or legislators who resist or oppose the standard public health measures used to control epidemics of contagious respiratory disease specifically mask and vaccine mandates. Quantification of the harm that is causing awaits the scrutiny of epidemiologists.

Breakthrough Covid cases-how many vaccinated ? Unvaccinated ?

 In the pre Delta variant era the vaccines were thought to be the answer. The expectation and hope were that a vaccine could provide immunity, stop spread and push us all to the elusive herd immunity and life would return to the pre Pandemic norm.

And for while it  appeared that was the case.As cases numbers dipped lower and lower by the spring 2021 it appears that the worse was over at least in the US and by May  2021 the CDC believed it was time for the fully vaccinated to no longer wear masks with a few exceptions noted ( eg the immunocompromised, in health care setting etc)

But then the Delta variant spread rapidly mainly in the southern states whose vaccination numbers lagged behind. Data from Israel and the US now seemed to indicate that fully vaccinated (FV) people could not only contract Delta but they could spread it.A wedding outbreak in Houston seemed to indicate that fully vaccinated people could spread it to each other. We were learning that Delta was definitely more contagious and data from Canada and Scotland suggested it was also more virulent. 

So while the vaccine promises were not met in some regards it was believed and regularly quoted by the public health and vaccine experts that the vaccine really worked well in that serious disease -the type requiring ICU care,was quite rare. 

Even with or  perhaps because of the unpresented avalanche of covid data published it has been difficult to determine how common are breakthrough cases, how frequent are the serious cases and who does it mainly attack ( is it only a disease of the unvaccinated?) ?  

Data from Israel is instructive. Israel is like an experimental lab for the world.Israel has 78% of its citizens who are over age 12 years fully vaccinated. Most if not all of the citizens are members of one of the HMOs which collect individualized  data which seems to be quickly available for analysis.

Israel is in a Delta surge . A 78% vaccination level is not high enough to prevent Delta surges. 

As of data from August 15 2021 there are 514 patients in hospital. Of those 59% are fully vaccinated  and 87% are over age 60 years. See foot note 1

In Israel serious breakthrough Covid 19 due to delta variation is not rare.

Is serious breakthrough really rare in the US or do we just have not the data to know what is going on with Delta?  Eric Topol and Dr L Wen have been critical of CDC for our flying blind predicament.

Antibody levels have been shown to be decreased at 6 months for both Moderna and Pfizer. Antibody responses in the elderly have been shown to be lower  Does that explain the preponderance of older patients in the Israel ICUs. Increased infectiousness of Delta and decreased antibody levels in patients immunized 6 month or more ago are suspects in regard to delta breakthroughs.intensified by less public attention to masking and distancing.

The case is strong for older folks both vaccinated and unvaccinated to wear masks in congregate settings and the CDC has recommended that as they walked back their May proclamation of no masks for most of the vaccinated.It seeems as if the public heard and remembered the CDC May advice but not their retraction or so it seems based on my personal observation of how few people in Harris County Texas are wearing masks. 

Will the booster fix the covid surge? Well, already Israel has reported 37  breakthroughs  after the booster shot but also have reported strong neutralizing antibody response to a booster mRNA jab. 

 foot note1)

Jeffery Morris (1) offers a illuminating discussion of the Israeli data in which  he demonstrates that when  the overall aggregate data are used the vaccine efficacy is calculated to be lower than it is in either group when the population is stratified  into two groups by age which we are told is an example of Simpson's paradox. His argument is that the "real" VE for serious disease is not as suggested by computing a VE based on the aggregate  data. My take is that  yes  the loss of efficacy for severe disease is not as great as a simple data display would suggest but my main point ,ie the breakthrough cases are not rare, seems solid .

1)Morris,J.  Israeli Data- how can efficacy versus severe disease be strong ... www.covid.data science

Will the current non-plan of "Maybe delta will have a rapid downturn " really work?

 As the delta wave continues to surge steeply upward some optimistic public experts project that US will see the rapid downturn in attack rate noted in England It is nice to think so but...

The US differs from England in at least the following ways:

1.England gave their second dose later than in the US perhaps giving the vaccinated a higher antibody level when Delta landed onshore  

2.  Some or many Brits continued to wear masks even after the controls were lifted.Arguably to a higher degree than in US.

3) England did not have powerful  elected regional leaders actively opposing mask wearing as governors of several  states in the US are now doing.

Dr Eric Topol is critical of the CDC current performance. First CDC was premature in their announcement in May that masks were no longer necesary for the fully vaccinated. The next mistake, in his view and in that of Dr. Leana Wen was to discontinued surveillance of breakthrough cases that were not serious enough to require hospitalization. Further according to Topol they should be doing genomic analysis on breakthrough cases and studying their antibody levels and noting  when and what kind of vaccine they received.  Basically Topol is saying we are flying blind  regarding the delta surge.Additionally CDC is admixing breakthrough case numbers from the pre delta times frame with those of the post delta period giving a falsely optimistic estimate of the fatality rate which in turn tends to negate the impact of their "wear mask again" advice.

From my admittedly limited personal experience in Texas  people just do not seem to be taking the surge seriously. This should not be surprising   One elderly  family friend eats out serval times a week and is now to attend a mini high school reunion Another elderly couple is planning a family union. A large local church is still living by the May CDC recommendations ignoring the most recent CDC advice as well as a recommendations by the county commissioner.Looking over the crowds at the  Astros game, only a few masks are seen. Local  authorities  have been forbidden by executive order to issue mask mandates even though delta is clearly more contagious and arguably more virulent  than the version of covid dominant in earlier surges.

Why does the Pfizer vaccine seem to work significantly less well In Israel

 Data (1) are available regarding effectiveness of   the Pfizer 2 dose mRNA vaccine in Israel,Canada and England/Scotland.

As regards the vaccine effectiveness  (VE) against the Delta variant  there is a wide difference  in the  values for VE for symptomatic disease .For Canada and England/Scotland there are  values of 87 % and 89% versus 64% for Israel.

Both Canada and England/Scotland administered the vaccine not according to the time frame used in the clinical trails for  Pfizer. Due as in part to a  shortage of vaccine in Canada a decision was made to give the second short 4 months after the first .

 In England/Scotland  a similar decision was made to postpone the second shot to maximize the number of  people who received the first shot as the alpha variant was surging at that time.This was done with the realization that they using a dosing schedule different from that used in the clinical trials which is inconsistent with standard method of applying clinical trial results to clinical practice. The British decision was controversial. Some suggested that a partially immune population ( i.e many folks with only a single jab) along with a surge in cases was a set up for a  perfect storm of super surging.

  In Israel, which was not facing a vaccine shortage,the decision was made to give the vaccine according to the time schedule that was carried out in the clinical trials.Also in the US The mRNA vaccines were given according to the time schedule used in the trials.So, will the data for the US show a pattern more like Israel or\more like Canada?

One explanation for the international disparity in vaccine effectiveness  is that the longer delay between doses of the mRNA vaccine results in a more robust  protective response. Could this be another example of "sometimes it is better to be lucky than good"? Perhaps confounding the comparison is the fact that the degree to which Delta was prevalent in the populations varied, i.e.  possibly more Delta at the time of the Israel data compilation. 

1) I based this blog  in part on a slide presented by CDC on or about July 30, 2021 which I believe in turn was derived from several sources including Sheikh,  a. SARs-COV 2-Delta in Scotland.Lancet vol 397 p 2461,June 26 2021 

and an article by B Lopez et al Effectiveness of Covid 19 vaccines against the B.1.617.2 (Delta) variant NEJM July 21, 2021