I wrote the following in my newsletter on 1) herd immunity and 2) vaccines.
There have been numerous models that attempt to come up with a number and I have reported on most of them. Percentage of infected needed to achieve herd immunity range from 20 to just over 70%. Part of New York City are thought to have achieved this if the value is at the lower end of the range. However, this may not be the case as it only applies to the stochastic case of a closed system. If Queens can be isolated from the outside, herd immunity may exist. However, if the value for herd immunity is 30%, then 70% are still naïve and subject to infection. Travel in and out of Queens will subject those people to potential infection. One simple example as to how this happens are the sporadic outbreaks of measles in the US because of insufficient vaccine compliance. According to CDC, 91.5% of children receive MMR vaccination and yet outbreaks still occur. Does this mean that herd immunity for this disease is greater than 91% (quite a high number!)? No, it just means that there are variables that we still don’t fully understand. As the famous literary and film quote goes, “it’s complicated!”
Apparently President Trump’s chief of staff, Mark Meadows, does not know how clinical trials work. Subjects need to be enrolled, data needs to be gathered, and case reports need to be analyzed and quantified. Unless Mr. Meadows knows of some magic way to find a shortcut, the time to do the trial and analysis is easy to quantify. Let’s look at the Pfizer m-RNA vaccine. This past Friday, Pfizer said they had enrolled 11,000 of the 30,000 patients needed. Two injections are required, the second one is 21 days from the initial shot. The vaccine is being tested globally, currently enrolling in the US, Brazil, and Argentina with additional enrollment in Germany, Turkey, and South Africa. Assuming enrollment is completed early September, the two-shot vaccination regimen will be completed by the end of that month at the latest. I do not know what the evaluation time frame to judge how protective the vaccine is. According to the trial description, confirmed COVID-19 cases are measured beginning seven days after the second vaccination. Pfizer say the expected end date for the trial is November 11. This means the last enrolled patient would be observed for about six weeks If I have done my math correctly. The linked press release states Pfizer may be in a position to seek regulatory review as early as this October and perhaps they will have compelling but incomplete data if that is the goal. This assumes everything goes right with the trial. One further note, Pfizer indicate 100 million doses would be ready by the end of the year. With a two-dose regimen, this would be enough to immunize 50m. We do not know whether all of these 50m would be available to the US.
Personally, I am not a fan of the gene based vaccines as I do not think they will provide enough immunity for those of us over 65. Those of you in this category who received the new shingles vaccine know first hand what it's like to get a super-potent vaccine. It has a lot of antigen and a new adjuvant that jack the immune system into producing a strong response. There is only one near term vaccine that fits this bill and that is the one made by Novavax. Sanofi/GSK are working on one but I don't know the time frame. GSK make the shingles vaccine and have developed the adjuvant as well.
