Thread by @EricTopol

The diagnosis and denial of waning immunity from Delta infections (*does not pertain to hospitalizations or deaths*)
In July, @IsraelMOH issued a report that showed a marked decline in mRNA vaccine (@Pfizer) protection vs Delta infections, down to 40%. That was met with disbelief

There are now 5 mRNA vaccine effectiveness studies for preventing Delta infections, and more on the way. Except for @PHE_UK, all show a marked reduction, particularly for @Pfizer, but the @moderna_tx comparison is confounded by its later administration (less chance to see waning)

This reduction of protection is quite different from the 6-month follow up of the Pfizer and Moderna pivotal trials which showed modest decline, but were against the original strain, not Delta
medrxiv.org/content/10.110…
nytimes.com/2021/08/05/wor…

This vulnerability to infections appears to be driven by time since vaccine, such as seen in this Israeli analysis. The age trend is noted, not statistically significant
medrxiv.org/content/10.110…

Why the differences between Pfizer and Moderna?
They are likely considerably less and skewed due to longer time from Pfizer vaccine, not accounted for in the studies. But there may still be a gap, with the higher relative dose and slightly (1 week) longer spacing

Which brings me to the outlier @PHE_UK report which suggests there was preserved VE for Pfizer. Again we don't know the time from vaccination which may have been shorter. The longer spacing, up to 12 weeks, may have induced a stronger immune response.

The data for neutralizing antibody titer decline and its association with risk of Delta infection has become clear from multiple studies, such as the Vietnam report in healthcare workers with infections papers.ssrn.com/sol3/papers.cf…

Bottom line: There is clearcut evidence of waning immunity for mRNA vaccines vs Delta infections, pronounced with Pfizer, but very likely affecting Moderna too. My estimate yesterday of 50-60% was likely optimistic as we get beyond 6 months + more exposure.

These findings are important regarding the consideration for boosters. Health care workers and older individuals are the people most likely to now be >5-6 months out from vaccination and are at increased risk for Delta infections