COVID19 update, November 10, 2020: Good news on Pfizer vaccine; whole-country testing in Slovakia

With all the news about the US election, you might wonder if I have forgotten about COVID19. There is, in fact, some big news.

(1) Dr. John Campbell shares with us the good news on the Stage 3 trial of the Pfizer vaccine.

Let me quickly share the gist with you. Pfizer’s vaccine is an mRNA (messenger RNA) vaccine, specifically a piece of RNA that encodes the viral spike protein, rather than a piece of spike protein itself. Downside is: it requires deep-freeze (just –18°C=0°F) for transport and storage. Upside: production can be scaled up very quickly.

The trial so far had 43,538 volunteers from six countries in it, with a range of ages, ethnicities, and comorbidities. The volunteers were divided into two equal-sized subgroups, as closely matched in composition as possible. One-half were given the vaccine, the other half a placebo. They were encouraged to go about their daily lives in the community, with their usual protection or lack thereof.

94 people caught COVID19. Drumroll… 90% of those were in the placebo group. Hence Pfizer’s claim that the vaccine is 90% effective, which is actually quite high for this type of vaccines — much better than the 10-60% of seasonal flu vaccines, and better than the 78% of mumps vaccine, but not as good as the 99% immunity from measles that two-dose MMR can achieve.

This was an interim report: the trial will continue to enroll new volunteers until they have at least 164 cases total.

You could get statistics on effectively with fewer people if you found brave volunteers for a “challenge trial” (i.e., people who agree to be deliberately administered the live pathogen). But then you would still need to do the large-scale trial anyway to establish safety. Better to just do the whole Stage 3 trial then.

Papers will be submitted for an EUA (emergency use authorization) in the US. The UK has preordered 40 million doses.

Dr. Campbell predicts several more vaccines will be announced in the next weeks. He sees this as a good thing: some of them may have better safety or efficacy profiles for some age groups and populations.

How long the protection is good for? Time will have to tell. Immunity against the four common cold coronaviruses (which account for 15% of all common colds) is quite short-lived: on the other hand, people who got SARS-CoV-1 seventeen years ago still show immune response. His educated guess is that the SARS-CoV-2 vaccine will fall in the middle.

(2) Mrs. Arbel drew my attention to an article in the WSJ about Slovakia’s “whole-country testing” experiment. Basically they on one weekend administered SDBiosensor antibody tests to their entire population. (RT-PCR testing on that scale is simply not realistic.)

Why not do the same elsewhere? Belgium is now considering the same option.

An Israeli insider, however, told me the following (my paraphrase of a phone conversation): False positives (FP) would be a few %, which means that at an actual prevalence rate under 1% in the population, most of the “positives” are likely FP. If we applied the same in Israel, we would have to put about 100,000 people in isolation — and many would violate their quarantine if they realized they were likely false positives. Furthermore, test of this type usually have 20-30% false negatives, so you would have to repeat the “test weekend” process a few times to be sure you catch at least most.

Instead, my source told me, monitoring and enforcing isolation, combined with track & trace, would allow us to keep things under control with about 20,000 tests/day. If people who tested positive routinely break isolation (and we know this happens), then no amount of TT&T will cut off the infection chains.