People asked for some info about the FDA approval process. Here is basic information on the regulatory process for approval of a vaccine. (FDA Basics) Here is some basic guidance on the emergency use authorization, which maybe will help tamp down some of the misinformation being spread about how that approval works. (FDA Guidance) These are easy to read and give you a sense of the process used to develop and approve a vaccine. I just want to reassure people that nothing unusual happened here. This isn’t the first time that the FDA has had to deal with a hurry-up process for a vaccine. So don’t fall for whacko conspiracy theories and other nonsense about the FDA and the CV-19 vaccines.
We keep hearing about how the Delta variant is so much more transmissible. I don’t buy that yet. And this article, examining the spread of another variant in Europe, is a cautionary tale on why we should be cautious about claims of greater contagiousness. As the authors detail, epidemiological factors, like general prevalence, number of introductions in a population and relative rates of spread in areas with different rates of variant spread, can explain what appears to be a transmission advantage. (Nature Article) The only way to identify for sure that a variant is more transmissible is to specifically show that across two pretty identical group of people, if they were infected with Alpha and then with Delta, there would be more infections in the same time with Delta. Just as with Alpha, I think we will ultimately see no transmission difference. And just because mechanistically a variant may have the capability to infect a cell more easily does not translate to greater infectiousness. But terrorists gonna terror.
This is a great article if you are interested in the detailed explaination of how CV-19 gets into cells. But the authors have to throw in the obligatory Delta terrorism. (Nature Article)
This is an interesting study on the association between rates of homebound adults over 70 and CV-19. While nursing home residents have been the primary casualty of the epidemic, older adults living at home also have endured significant mortality. The US has pushed “aging in place” so that more of the frail elderly are not in nursing homes than are in them. The researchers ascertained that in 2020 there was a significant increase in these homebound older adults, likely because people were avoiding nursing homes. Yet many of these persons are now in multigenerational and large households where they may also have exposure to CV-19. (JAMA Article)
Here is a research letter from the UK on whether vaccination affects rates of household transmission. Vaccinated persons were half as likely to transmit CV-19 to an unvaccinated household member as were unvaccinated index cases. Now what is interesting is that there was some household transmission by vaxed index persons. But there was no information about viral loads or disease severity. And the study reminds us than contact tracing and testing was just another huge failed intervention with a ton of cost and little value. When you read these studies, remember that researchers often don’t actually know who the index case was or how any secondary cases in a household got infected. (NEJM Article)
There are a lot of really smart scientists and researchers in China, so I hate having to always give this warning, but the government there controls everything so you just have to be cognizant of that when you read studies from that country. These researchers were looking at transmission patterns in China. (JAMA Article) The likelihood of transmission from an index patient was found to be greatest two days before and three days after symptom development. Overall transmission rate was a measly 3.6%, as 730 index patients transmitted to only 327 persons out of around 8852 close contacts. Note that this is an R(t) of under .5. The rate of transmission by asymptomatic persons was one-third that of symptomatic ones. Asymptomatic index cases were likely to transmit asymptomatic cases, suggesting lower viral loads and infectiousness.
Not sure how much more trustworthy research from Russia is. The country has its own CV-19 vaccine and this study says it was about 80% effective in preventing hospitalization. (Medrxiv Paper)
Delta is going to kill us all is the theme of the day. Another study that examines vaccine effectiveness against Delta, comparing it to Alpha and looking at the characteristics of breakthrough infections. (Medrxiv Paper) The research was done in Portugal and looks like a very solid case comparison design. One big caution is that the comparison is made at a different point in the Alpha wave and the Delta wave. 12% of Delta cases were among vaccinated persons, versus 5% of Alpha ones, but again, very different percents of the population were vaccinated during the relative waves of these strains. Delta breakthroughs were said to have a higher viral load and to have less difference between vaccinated and unvaccinated persons’ viral loads, but Delta viral loads in the vaxed were still noticeably lower than in the unvaxed. On an adjusted basis, however, there was a very minor difference in viral load in the unvaccinated between Alpha and Delta, and no difference for partially or fully vaxed persons. The authors infer greatly transmissibility of Delta. I always wonder about that inference. Does a higher viral load always mean greater infectiousness? That assumption should be tested, and we have the lingering problem that if vaxed people generally have lower viral loads and a different curve of viral load over time, then when people are tested in the curve could be misleading as to average viral loads.
If you really want to freak out, this study from Japan claims that the Delta variant is itself mutating in a manner that will allow it to completely avoid neutralization by antibodies stemming from the vaccines. (Medrxiv Paper)
This is a very large study from England on clotting issues following vaccination. They basically surveyed the entire population using electronic medical records and vax records. For persons over 70, there was no distinguishable uptick in clotting issues following vaccination. For younger persons there was a very slight increase in events amounting to one in a million persons. Another greatly exaggerated vaccine risk. (Medrxiv Paper)