Finally, some data on antibodies…

… from the Pfizer booster application

As we previously posted…

Pfizer presented data indicating that the efficacy of its vaccine in preventing hospitalization only wanes slightly … from around 90% shortly after 2nd shots to about 85% 6 months later.


That’s a strong commendation for the efficacy (and durability) of the vaccine … but, it’s a relatively weak case for boosters.


But, Pfizer also submitted data indicating that effectiveness against infection starts high (90% immediately after the 2nd shot) …  but it wanes down to around 40% 6 months later.


That’s a pretty strong case for boosters since any infection brings with it (1) the threat of “long covid” complications (2) the accompanying risk of hospitalization and death (3) the likelihood of transmitting the virus to others.


Supporting the data re: the waning protection from infection (and the case for boosters), Pfizer also submitted some data re: “neutralizing antibody titers” … a clinical assessment derived from from a specialized blood test.


The way antibody titers are measured (and reported) is complicated.

For an explanation, see What is an Antibody Titer?

In a nutshell: higher titers mean more antibodies … and more antibodies means more immunization.

According to Pfizer, vaccine recipients have an average of 762 titers one month after receiving their 2nd dose.

That’s good … it’s a level that provides about 90% protection against infection.

But, over time (6 months) the titers’ level drops about 80% … down to 136.

That’s not so good …  it’s only strong enough to provide 40% to 50% protection against infection.

A booster shot generates a 17 times increase in the pre-booster titer level … boosting it from 136 to 2,374.

That’s very good … it’s about 3 times the post-2nd shot level … suggesting near total infection immunity.

That is, of course, subject to waning protection over time.

But, 2,374 is a very high level which, taking the Pfizer data at face value, can wane down to 762 and still provide about 90% protection against infections.

That’s a strong case for boosters!


DISCLAIMER: I’m not a medical professional or scientist — just a curious, self-interested guy.  So, don’t take anything that I say or write as medical advice. Get that from your doctor!

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