Dvir Aran Profile picture
21 Jul, 17 tweets, 4 min read
Are we seeing immunity waning in Israel? The MoH shared some raw data, and together with @geller_mic we tried to get a qualitative answer to this question. TL;DR – it seems that there is immunity waning, increasing risk of infection of early vaccinated by ~80%. ==>
Several remarks before we start:
1. This is a qualitative analysis. We don’t have data on individuals, only very limited information shared by the MoH.
2. We are talking about immunity waning, not vaccine effectiveness. Delta may affect VE, but data here is independent of that
3. The analysis below is on the risk of infection, not severe disease. I wrote about VE of severe disease in a different thread.
4. This is twitter science, take it as it is. There are many assumptions and caveats to this analysis.
After we cleared the table, let's dive into the data. By the end of January ~1.8 million Israeli already received their second dose. Below is data of confirmed cases in this cohort (left >60+, right 16-59). Image
Let’s start with the younger group, about 770K individuals. It says 16 and older, but almost all are 20+. In the week of July 4-10 there were 350 cases. In all of the vaccinated population in this age group there were 1056 cases (33%), so 706 cases in “late” vaccinated.
The problem is that it's not clear what proportion of the population was vaccinated early. 770K is 18%, but this is problematic. It includes non-vaccinated, ultra-orthodox and Arab citizens (the current wave has not spread to those groups yet).
We looked at how many were vaccinated in “general” pop cities, and we estimate it at about 22%. If this is the background that we need to compare to, it means that early vaccinated are at ~75% higher risk for infection. If VE is ~90%, after half a year it drops to ~82.5%.
An explanation on the calculation: based on those numbers our expectation in early group is = 706 cases * 0.22/0.78 ~= 200 --> 350/200 = 1.75
Now to adults. Here we have 370 cases in early vaccinated from 421 total (88%). What is the expected rate? We estimate it at about 79% of 60+ in the general population. This translates to about a factor of 2 in risk, or if VE is 90% then after half a year later it drops to 80%.
We also looked at the week of July 11-17. The results from that week are more or less the same. This brings us to about 80% increased risk for early vaccinated vs. late vaccinated in both age groups.
Delta might affect VE, but it's very hard to estimate it based on Israeli data. The data suggest that non-vaccinated adult individuals are reluctant to get tested, which skews calculations towards very low levels of VE.
I personally think that Delta VE is still around 90% for infection, but we will have to wait for better studies. Our analysis does show that after half a year or so this 90% drops to around 82%. It’s a significant reduction, but not a game-changer.
Note that we are comparing here vaccinated individuals to vaccinated individuals. It still might be that “late” vaccinated individuals tend to get tested at lower rates or other biases we can’t assess here.
In conclusion, we are seeing immunity waning. It's disturbing on its own, however it is likely that the vaccine is still working quite well. More rigorous research is required to confirmed our estimates.
and now from the MoH released their analyses.

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More from @dvir_a

27 Jul
Vaccine impact in Israel: changing trends. Analysis thread with @AArgoetti.
From about a month and a half ago we are experiencing a new “Delta” burst. Cases are accumulating, and more and more severe patients are in the hospitals.
You’ve probably seen reports from Israel on low vaccine effectiveness in this wave. Is it because of Delta? Waning immunity? We think the reason is mostly that we got the denominator wrong.
See this graph. Until mid-July, the number (normalized to group size) of severe cases in the 65+ group was more or less similar between vaccined and unvaccined. This seemed troubling. But in the last 10 days trends have changed,
Read 9 tweets
24 Jul
אז בעקבות הציוץ של @Nadav_Eyal ביום שישי ״זכיתי״ לחטוף את עוצמות הסחל׳ה של הטוויטר הישראלי. כיף. באמת מבאס שאנשים מרשים לעצמם להתבטא בצורה כזו ומשתמשים בתיבת תהודה עצמית כדי להוריד את רמת השיח לרמות תחתית. זה לא משהו שלא ידעתי, רק שזה באמת שונה שזה מכוון אליך.
אין לי עניין מיוחד לתת במה לגועל הזה, ולכן לא אשתף. אבל האמת שאני מרגיש שזה קצת מגיע לי כי כנראה בשבוע האחרון גם אני קצת התדרדרתי לרמת שיח לא מכבדת, ואני מבטיח לעשות מאמץ להימנע מזה להבא.
בואו נתמקד בעיקר. אולי הדבר המרכזי ביותר שצריך לעשות במחקר הוא להגדיר בצורה נכונה את קבוצת הביקורת. לשום ממצא אין ערך בלי השוואה נכונה לקבוצת ביקורת. כשמסתכלים על 235 סוגי ההטיות שהגדיר יואנידיס מגלים שרבות מהן קשורות לבעיה הזו של חוסר התאמה בין קבוצת ההתערבות ולקבוצת הביקורת.
Read 19 tweets
21 Jul
Waning immunity, take 2. More data from MoH. The plot speaks for itself. X-axis is the week of vaccination, y-axis is the relative risk for infection in last two weeks. Data suggests that early vaxxed risk for infection is doubled compared to late vaccinated. With @geller_mic.
What can explain this trend except waning?
Maybe early vaxxed are more aware of COVID-19 and get tested at higher rates. This can be tested by the MoH.
Read 4 tweets
20 Jul
האם יש דעיכה בחיסוניות? משרד הבריאות פרסם קצת מידע גולמי אתמול ויחד עם @geller_mic ניסינו לקבל הערכה איכותית לשאלה הזו. אמל״ק – יש, אבל זה לא כזה דרמטי (כרגע).
שתי הערות מקדמיות: 1. זו אנליזה איכותית. אין לנו נתונים על אנשים, רק המידע החלקי שמתפרסם ע״י משרד הבריאות. מתישהו כללית, מכבי ומשהב״ר יפרסמו את האנליזות שלהם. עד אז זה מה יש.
2. אנחנו מדברים פה על הדעיכה של החיסוניות, לא על היעילות מול דלתא.
3. זה ציוץ בטוויטר, לא מאמר מדעי...
אז אחרי שהבהרנו את זה, בואו נצלול למידע שהתפרסם. עד סוף ינואר 1.8 מליון איש קיבלו את המנה השניה. בנתונים אפשר לראות מה קרה לקבוצה זו של מתחסנים מוקדמים בשבועות האחרונים – כמה אימותים וכמה חולים קשה, מחולק לשתי קבוצות גיל.
Read 11 tweets
19 Jul
בואו נדבר שוב על נתב״ג. למה אני חושב שזה מקור כל הצרה?

אז קודם כל נתונים, מתחילת יולי (עד ה-17 לחודש) היו 9,169 מאומתים, מתוכם 922 הגיעו מחו״ל. תעשו את החשבון לבד. אם ה-R שלנו הוא 1.3, בלי מאומתי נתב״ג אנחנו ב-1.17, בערך חצי מהדרך להקטנת ההתפשטות.
אבל זה רק חישוב נאיבי. אין לי את המספרים המדויקים, אבל בהנחה שנכנסים 20,000 איש ביום לישראל, כ-0.25% מהחוזרים נושאים את הנגיף. באותה תקופה, הסיכוי היומי להדבק בכלל האוכלוסיה ~0.005%. זה יחס של פי 50.
כלומר, הסיכוי של חוזר מנתב״ג להיות חולה ולהדביק אחרים הוא פי 50 (!!!) מאשר אדם אקראי. גם אם יש תת-אבחון בישראל, זה מקסימום פקטור של 2, לא מתקרב ל-50.
Read 6 tweets
18 Jul
Finally, some data from Israel on vaccine effectiveness. Before we start, a couple of comments: 1. Almost all new infections in Israel are with the delta variant. 2. We don’t believe confirmed cases count since there are complicated incentives for testings.
The data that we look at is new severe hospitalizations by age group and vaccination status. Let's look at the numbers:

Since the start of July, there were 117 severe cases. Of them, 79 in ages 60+, 28 in ages 40-60 and 10 below 40.
> In the 40-60 group (blue), 8 of the 28 were vaccinated (29%). About 85% of this group is vaccinated, so this translated to ~90% effectiveness. More or less what we expect. Great. (below 40, there are 10 unvaccinated severe patients)
Read 9 tweets

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