Emerging Data on Booster Shots

I wanted to revisit the question of COVID vaccine booster shots, or rather third doses of the vaccine which are now being administered in Israel and will be in the United States starting next month. (Those with compromised immune systems have already been approved for third doses in the United States.)

The short version is that initial data out of Israel appears to show dramatically increased protection both against infection and disease from a third dose. But there are at least some questions about the data and what they actually mean.

There are two studies or at least two sources of data. One is from Maccabi Health Services, one of the four HMOs that makes up the Israeli national health care system. They looked at 149,144 people who had gotten a third booster and 675,630 who had two shots. Only 37 people in the first group had gotten infected compared to 1,064 of the latter. The booster shot cut the risk of infection by 86% and the risk of severe disease by 92%.

Those effectiveness numbers don’t sound that different from what we’ve been told for some time. But in July the country’s Ministry of Health had placed the protection against infection provided by the two shot regimen as having fallen to 39% during the period between June 20th and July 17.

In other words, if we think these two measures, before and after, are both accurate and comparable, that’s a pretty dramatic improvement.

On Sunday the country’s Ministry of Health published additional information. These findings found that people over 60 who received a third dose had four times higher protection against infection than those with two doses. Protection against serious illness and hospitalization increased between five and six-fold. In other words, these are, on their face, huge increases in protection.

But there are a few complications.

The first is that Israel has been reporting very low effectiveness for the vaccine during July and August, especially against infection. There’s been a running debate over whether those findings are accurate, though the weight of expert opinion seems to have moved in the direction of these low effectiveness against infection findings.

The key point here is that these really dramatic increases in effectiveness are based on findings that say effectiveness had dropped pretty substantially, again especially against infection. With those low effectiveness starting points the big strides from a third dose become much less dramatic. Just basic math.

In the case of the newly released Ministry of Health findings they released only the topline findings. The underlying data experts would want to look at to kick the tires was not released, at least not yet.

Finally, each of these data points seems to be, as nearly as I can tell, different snapshots of effectiveness: one from this angle, one from that angle. Ideally, you’d want the same data, the same methodology and see the changes over time. But this doesn’t seem to be that.

One final point that occurred to me is that these findings were only for a very short period of time, like a week or two. Again, I’m a journalist with a history PhD. So maybe that’s meaningless. It just seemed like a question to me.

As is so often the case in this stage of the Pandemic we’re forced to make judgements on the basis of incomplete and sometime contradictory data. But if these results are even broadly accurate, you can see why the country has moved ahead rapidly to give the whole population three doses. They started with people over 60, where the biggest uptick in severe illness was occurring. They’ve rapidly expanded downward decade by decade. Starting next week they’ll offer it to everyone over 30.

There’s an additional debate among specialists trying to make sense of this data. There are two general schools of thought – though in practice it may be a combination of both possibilities. One holds that to the extent this data holds up it’s just acting as a booster. So maybe you need to give people shots every six months. You get a big boost at the front end and you’ll have a similar waning early next year. But others have a different theory. Maybe the dosing was just off. Maybe two doses is just wrong and three doses is the proper regimen, after which immunity remains robust and stable for a substantial period of time.

Needless to say, I have zero ability to litigate that question. But it’s a pretty basic question with immense significance.

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