Data Showing COVID Booster Waning Among Elderly Behind Israel's Fourth Dose Decision

An initial analysis presented to Israel’s coronavirus expert panel shows that people over 60 are three times more likely to get infected four months after getting their booster shot

Ido Efrati
Ido Efrati
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A woman prepares a COVID vaccine shot, in Jerusalem, on Thursday.
A woman prepares a COVID vaccine shot, in Jerusalem, on Thursday.Credit: Ohad Zwigenberg
Ido Efrati
Ido Efrati

Israel's pandemic advisory panel on Tuesday recommended administering a fourth dose of the coronavirus vaccine to vulnerable people on the basis of partial information, fearing the rapid spread of the omicron variant. The data that was considered by the panel revealed a significant waning in protection provided by the booster shot after a few months.

There are 850,000 people aged over 60 who received the booster dose more than four months ago, and they are three times more likely to get infected with coronavirus than people who just received the vaccine. The data also showed that there was a significant decrease in protection for elderly people who received the inoculation three months ago.

The head of Israel’s pandemic advisory panel, Dr. Boaz Lev, explained on Wednesday that “the rate of infection from omicron is enormous, unlike anything we saw with the previous variants. It is becoming the dominant variant in every country it appears in, and it is easy to see that it is taking over from delta [as the dominant variant].”

Lev stressed that the recommendation has been parked for the time being, and that the decision was made in fear of a lack of information about the severity of illness from the omicron variant.

An initial analysis conducted by researchers from the Health Ministry, Weizmann Institute, Technion, Hebrew University and Gertner Institute was presented to the panel on Tuesday and showed the rapid outbreak of coronavirus in countries where the omicron variant has gotten a foothold. In the 10 days that elapsed since the previous discussion, the number of omicron cases increased tenfold.

Several doses of the COVID vaccine, this month.

The researchers said the recommendation to roll out the first booster shot came at the end of July, about a month after the first cases of delta were discovered in Israel, but it still took a long time before the immunity provided by the third jab took effect in the country.

The researchers, however, believe that the faster spread of omicron leaves a smaller window to maneuver, writing that “clear information on severe cases of omicron may only be available by the time it is too late to protect at-risk populations.” They also presented a forecast showing that the daily number of omicron cases will reach 5,000 to 10,000 within two weeks.

If omicron does lead to serious illness, it will likely place a heavy burden on Israel’s health system, which will be exacerbated by seasonal flu outbreaks and the increase in quarantine of medical staff.

The head of the research team, Prof. Ron Milo of the Weizmann Institute, presented a preliminary analysis of the decline of the protection provided by the third vaccine against delta among those 60 and over. The data shows that the waning of protection from infection from two doses and three doses already begins after three months.

Milo presented a graph showing the number of infections per 100,000 risk-days (meaning days of potential exposure to the virus) among those 60 and over. In the first month after receiving the third dose – meaning the booster shot – there were two cases of infection.

In the second month, there were three cases of infection. In the third month, 3.5 cases and in the fourth, the number of infections approached five per 100,000 risk-days. In the fifth month, there were on average more than five infections per 100,000 risk-days.

The figures show that the third dose, the booster shot, provided a high level of protection – four times that of the second dose. But the presentation to the committee also included the following: “The noted protection against inflection with the delta variant for those vaccinated with the booster begins to erode.”

These figures relate to the delta variant, but researchers say the booster is even less effective against the omicron variant. And the researchers still don’t know what effect the omicron variant has in causing serious illness. “Preliminary analyses don’t show a decline in the effectiveness against serious illness,” they wrote, but added: “There is a problem in obtaining reliable results due to the small numbers and statistical error.”

The researchers conclude that a large and rapid wave of omicron infection is almost unavoidable, and that it appears the vaccine is significantly less effective in protecting against infection from the new variant. In addition to the more than 1 million Israelis 60 and over who were vaccinated with a booster more than three months ago and whose protection is already waning, there are roughly 72,000 who were vaccinated within the past two to three months and about 26,000 who were vaccinated in the past two months.

According to data presented at the committee session, about 14 percent of Israel’s population consists of recovered COVID patients, and it is thought that there are roughly the same number of recovered patients but whose illness and recovery have never been confirmed, including about half a million who receive the booster dose. This, the researchers say, is evidence of the possible safety of a fourth dose because they have not seen severe side effects among such undiagnosed recovered patients compared to the prior doses.

The coronavirus information center of the IDF Intelligence Corps made its own presentation on the declining effectiveness of the booster dose, noting that the protection afforded those who have received a third dose could be expected to decline among people 60 and over from 75 percent to 25 percent within a month. The center anticipates that the prospect of the omicron variant becoming dominant in Israel would transform the protection of the population from reasonable to nearly nil.

At least 30 percent of the population needs to be vaccinated again to halt the spread of the virus in the country, the center said, adding that this is not feasible.

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