@profshanecrotty Thanks @profshanecrotty for another super informative thread (ht @HelenBranswell for tweeting). My 2 cents is just to remember that the comparison between sero+ and sero- in the control arm in Novavax was not randomized and involved ~40 cases in each group.
@profshanecrotty @HelenBranswell Study was of course not designed to assess natural immunity, so kudos to the scientists for reporting these important data, but caution in interpretation. Several reasons to expect bias in observational seroprotection studies like this dash.harvard.edu/handle/1/37366…
@profshanecrotty @HelenBranswell In particular, those who got infected before (sero+) are likely still at high risk for subsequent infection(due to job, housing, use of transport, other persistent factors), leading to noncausal positive association betwn prior and future infection (confounding).
@profshanecrotty @HelenBranswell This is not the only possible direction of bias but it is a plausible one. Obviously if prior infection were perfectly protective we'd see no reinfections regardless of bias, but if it's partially protective, prior infection can look less than it is. Also academic.oup.com/aje/advance-ar…
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