[millettjon]

This paper from Africa Health Research Institute shows a 41x reduction in effectiveness of pfizer vaccine for omicron.

https://www.ahri.org/omicron-incompletely-escapes-immunity-i... https://www.ahri.org/wp-content/uploads/2021/12/MEDRXIV-2021...

[Brybry]

This preprint also shows reduced antibody neutralization of omicron in comparison to delta (including for double vaccinated + previous infection).

Note the sample sizes for all these studies is small. 12 participants for the AHRI paper and 8 to 20 per group for this one.

https://www.medrxiv.org/content/10.1101/2021.12.07.21267432v...

[swader999]

Sample size doesn't really matter much in this kind of study.

[peteradio]

Ideally you'd match it to some population of interest. For my own medical affairs, I don't care what grand-pappy's results are here, I want to know how cousin Tim fairs.

[Stanleyc23]

Why not? I’m no statistician, so my basic understanding is you should always prefer bigger sample sizes to ensure statistically significant findings.

[fsh]

This paper doesn't even attempt to measure effectiveness. It measures neutralization titers which is a totally different thing.