New data out of Israel appears to suggest substantial increased protection after a third shot of the Pfizer vaccine. I say ‘appears’ because like a lot of the real-time information emerging out of Israel it’s made up of current statistics rather than a study per se. And at least in the news accounts one has to read between the lines since some points are not stated explicitly.
In any case, the new results show 86% effectiveness against infection in people over 60 and 92% against sever disease. On its face that doesn’t sound that different from levels of protection we’ve thought you got from two doses, at least based on data from the US. But recent numbers from the Israeli Ministry of Health at least had shown the effectiveness against infection as low as 39% in late June and early July. So to the extent we’re looking at the difference between levels of protection they’re finding in Israel it’s a pretty big difference.
Let’s note here that this is effectiveness against infection. There’s an emerging body of evidence of reduced effectiveness against infection even as effectiveness against disease and severe disease seems much more durable.
According to the reports, they looked at 149,144 over 60 who’d gotten a third dose and 675,630 who only received two back in January and February. There were 37 confirmed infections in the first group and 1,064 in the second. On its face, that makes it sound like it’s pretty good to get a third dose.
Now, one other caveat about these reports. Israel only started giving boosters to people over 60 last month. The comparison put people in the three shot group when they were seven days out from the third injection. Point being it’s a pretty brief interval, albeit with a pretty sizable group.
The final point to bear in mind is that in data released earlier this month breakthrough infections resulting in severe illness were only cropping up in significant numbers among vaccinated people in their late 60s and up. You can see the data here. So the fact that these numbers are among people over 60 is a significant data point. The level of enhanced protection could be less among younger people.