Severe corona course despite vaccination: do the numbers in Israel prove a declining effectiveness against Delta?
A statistician warns of misinterpretation.
New York / Tel Aviv - What about Israel now? Pointing fingers at other countries in the coronavirus pandemic is nothing new. Israel is a particularly popular target for judging the vaccine and its effectiveness. That is not entirely unfounded. The country has long been a pioneer, especially when it comes to vaccinations. While there was still a dispute over the distribution of vaccination doses in Germany and Europe, the nine-million-nation state has already broken all records with its vaccination campaign. At the end of April, over half of the population was fully vaccinated.
Now the corona cases are increasing again in the model country, despite the high vaccination rate.
According to official data, over half of the Covid patients treated on August 15 in Israel are vaccinated.
Over 50 percent sounds drastic.
Is that now the proof that vaccines are becoming less effective?
Was all the hype in vain?
Not quite.
Researchers caution against being misled by such statistics.
Researcher explains the Israel paradox: be careful!
- the vaccination rate can lead to incorrect assumptions
Biostatistician Professor Jeffrey S. Morris calculates it on his Twitter account and writes: "Many are confused by the information that more than half of all hospital patients in Israel are vaccinated and think that the vaccinations are not working." However, the official data of the country has been analyzed and they show: Actually, the data prove exactly the opposite, namely that the corona vaccines "are very effective against a severe course."
One of the deciding factors is the high vaccination rate in Israel.
The higher the proportion of vaccinated people in the population, the higher the proportion of people who get corona despite being vaccinated.
If everyone were vaccinated, the quota would ultimately be 100 percent.
If one takes into account the high proportion of fully vaccinated people in Israel, one has to reinterpret the data.
The Israel paradox explained: vaccinated or unvaccinated - who suffers a severe corona course more often?
Morris shows how it is done.
He calculates Israel's official Corona numbers and compares the number of serious Covid hospital cases in people with and without a vaccination.
(each from 12 years).
He wants to find out: which group has more severe courses in percentage terms - vaccinated or unvaccinated?
If the vaccine were not effective, the result should be exactly the same for both numbers.
But it is not.
"You can see that the proportion of severe Covid cases in unvaccinated people is three times as high." But the calculation does not end there.
Because age also plays a significant role.
Israel paradox explained: Corona statistics deceptive - vaccine effectiveness at at least 85 percent
7/8 pic.twitter.com/01Z9BS3Z9S
- Prof Jeffrey S Morris (@ jsm2334) August 17, 2021
Because: The majority of all those who have not been vaccinated are young. Almost all elderly at risk patients are vaccinated. According to Morris, a paradox arises here, which is also called "Simpson's Paradox": Although the effectiveness in under 50-year-olds is 91 percent and in over 50-year-olds 85 percent, it is only 67 percent overall. (See table) The elderly group is to blame: Here the proportion of people who have been vaccinated is significantly higher, but so is the risk of a severe course. That pushes the entire statistics down.
The example of Israel shows “that the Biontech / Pfizer vaccine scores very well against Delta in preventing serious diseases,” explains the biostatistician in a detailed article on his calculation.
In the end, the effectiveness is 85 to 90 percent, despite the irritating hospital figures.
This is also confirmed by previous studies and findings.
Serious breakthroughs in vaccination remain comparatively rare in Israel.
The problem of the declining willingness to vaccinate is much greater.
It is also falling in Israel.
The vaccination rate has barely increased since May.
The Delta variant has an easy job.
The example also shows how difficult it can be to take a differentiated look at statistical data on the corona crisis without jumping to conclusions.
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