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Today a story has been going around about a cluster of B.1.617 cases in Israel. This is the India-associated strain.
Unfortunately, this is in some places being spun as a possible example of vaccine escape. But the numbers suggest exactly the opposite! https://www.timesofisrael.com/children-from-5-schools-among-israels-41-cases-of-indian-covid-strain/
Unfortunately, this is in some places being spun as a possible example of vaccine escape. But the numbers suggest exactly the opposite! https://www.timesofisrael.com/children-from-5-schools-among-israels-41-cases-of-indian-covid-strain/
Here are the numbers.
24 with recent travel history.
17 with no travel history
5 children
4 vaccinated
Approximately 85% of the adult population in Israel has been fully vaccinated. So what does this tell us about vaccine effectiveness against B.1.617 in adults?
24 with recent travel history.
17 with no travel history
5 children
4 vaccinated
Approximately 85% of the adult population in Israel has been fully vaccinated. So what does this tell us about vaccine effectiveness against B.1.617 in adults?
I'll just do point estimates.
Assume the 5 children were <16 and thus unvaccinated.
That gives us 32 cases among unvaccinated adults, and 4 cases among vaccinated adults.
The basic calculation for effectiveness then gives us a remarkable 98% against B.1.617.
Assume the 5 children were <16 and thus unvaccinated.
That gives us 32 cases among unvaccinated adults, and 4 cases among vaccinated adults.
The basic calculation for effectiveness then gives us a remarkable 98% against B.1.617.
But those with travel histories may have had much worse exposures, you might object.
Fair enough.
Let's look just at the people with no travel history.
We don't know this, but let's assume the worst-case for the vaccine: all 5 children+4 vaxxed had no travel history.
Fair enough.
Let's look just at the people with no travel history.
We don't know this, but let's assume the worst-case for the vaccine: all 5 children+4 vaxxed had no travel history.
Now—even with these worst-case assumptions—we end up with an estimate of 92% effectiveness for the vaccine.
So it seems that worst case, point estimates are that the Pfizer vaccine is as effective against B.1.617 as it is against wild type—might be even more effective.
So it seems that worst case, point estimates are that the Pfizer vaccine is as effective against B.1.617 as it is against wild type—might be even more effective.
