COVID Israel: 86% Increase in Effectiveness with 3rd Pfizer Dose

[bhobba]

Data has come in from Isreal about the effectiveness of a third dose:
https://www.straitstimes.com/world/...e-in-over-60s-says-israel-healthcare-provider

Remember this is 86% better than those that have already had two doses.

I will leave it to others to do the calculations but my initial calculation in the next post says we may be able to get heard immunity. Saying something like that is so important I would like others views.

Note: Edited to reflect more detailed calculation.

Thanks
Bill

 

[bhobba]

Ok, here is my detailed calculations. Vaccine effectiveness is 37/149144 = 99.975%. So the vaccination number is (1-1/6.9)/.99975 = 86%. It looks like my initial calculations may have been overly pessimistic. We could get herd immunity at greater than 86% vaccination. If true, it could have a big impact.

Thanks
Bill

 

[Ygggdrasil]

A key piece of information missing from the news article is how they measured protection. Is the figure they cite protection against symptomatic disease or protection against infection? Studies of the vaccine shows that protection against symptomatic disease is higher than protection against infection. However, these numbers would exclude people infected asymptomatically who are still capable of spreading the virus.

Some of your conclusions (esp. with regard to herd immunity) assume that the figures represent protection against infection, which is not clear in the article (measuring protection against infection is much harder to do as it requires regular testing, so it is unlikely that this study measured protection against infection).

This is why it is quite annoying when data gets released via the news media rather than from scientific publications or pre-prints detailing the methods used to collect and analyze the data.

 

[atyy]

From the other human coronaviruses, protection against infection will fall again with time. So I don't think this supports a stable herd immunity plan.

https://www.nature.com/articles/s41591-020-1083-1
"Caution should be taken when relying on policies that require long-term immunity, such as vaccination or natural infection to reach herd immunity. ... We show that reinfections by natural infection occur for all four seasonal coronaviruses, suggesting that it is a common feature for all human coronaviruses, including SARS-CoV-2. Reinfections occurred most frequently at 12 months after infection, indicating that protective immunity is only short-lived."

It will slow down transmission, and buy time for people to get vaccinated. But I think it ultimately requires people to get vaccinated to protect themselves against severe disease, rather than relying on others to get vaccinated.

 

[atyy]

Eran Segal: "Israel is reporting a 4-fold increase in protection from infection after a 3rd booster shot, compared to an age-gender matched cohort of 2 doses And 5-6 fold increased protection from hospitalization and severe disease 3rd dose now approved for all, tomorrow starting in 40+ y/o"