About life in the last third

The effectiveness of the vaccine against the Delta

I just wrote about the Delta variant and what I term PCR disease. Now I would like to say a bit more about the variant. Once again, please be reminded that I am expressing my opinion, and they should not be taken as facts.

Antivaxers are misrepresenting the data from Israel, for instance, either because they do not understand or worse, because they do. When the original clinical studies were done, 50% of subjects were vaccinated, and 50% were not (control group). The study then compared the number of subjects that had symptomatic disease with those that did. The conclusion was that the vaccine was 95% effective. That means that of the 100 classified as having COVID 19 (symptomatic), only 5% were from the vaccinated group.

Vaccinated with Symptoms: 5%
Unvaccinated with Symptoms: 95%
Total Subjects: 100%

It is easy to misunderstand these numbers. They do not say anything about how many people got ill. In the Pfizer study, only 170 out of 43,000 of the total population studied contracted the virus. The purpose of the study was to determine the ratio. It is assumed (and later verified) that this ratio would remain. Over time more of the subjects would contract the virus, but for every 100 that did, 95 would be from the unvaccinated group.

The study said nothing about how infectious the virus was. For example, if twice as many people got sick, but the ratio was the same, it would still be 95% effective.

Since half of the people were vaccinated and half not, we did not have to be concerned with the “base rate.” The base rate would be the percentage of people in each group that got ill. But now that people are vaccinated, we have to consider what percentage of the vaccinated group are getting ill versus the unvaccinated.

In Israel, more than 90% of those over 65 have been vaccinated. So if the vaccine were not effective, we would find that 90% of those infected would have been vaccinated. But let’s imagine that the vaccine is 90% effective in preventing severe illness. In this case, 10% of those infected would be from the vaccinated group and 10% from the unvaccinated group. This leads to the statement “half of those sick have been vaccinated,” which implies that the vaccine is not effective, but it is not true. It is essential to understand this.
For example:

Vaccinated 90% Percentage infected 10% 9 ill
Unvaccinated 10% 90% 9 ill
Total 100% 100%. 8 ill

This does not have to do with how infectious the virus is. It appears that the Delta is twice as infectious as the original Alpha. This could result in substantially more people in both the unvaccinated group and in the vaccinated group becoming infected.

When it comes to severe disease and mortality, we might find that the difference between the Alpha and Delta will not be twice. This is because I think that the Delta may develop faster in addition to getting more easily infected than the Alpha. This would result in more vaccinated people getting some symptoms before the immune response kicks in. I would expect that more people would have positive PCR test as a result. We might see the death rates as a percentage of infections increase for the unvaccinated because the unvaccinated immune response will not respond fast enough.

So bottom line, if it made sense to get vaccinated against the Alpha variant, it makes double sense to get vaccinated against the Delta.

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