Primary source: <a href="https://dx.doi.org/10.1097/AOG.0000000000004695" rel="nofollow">https://dx.doi.org/10.1097/AOG.0000000000004695</a><p>Couple interesting points:<p>- the effect size is less than one day<p>- they don’t have any data on actual SARS-CoV-2 infection<p>- time between doses seems to be a major factor:<p>> The increase in cycle length for both the first and second vaccine cycles appears to be driven largely by the 358 individuals who received both vaccine doses within a single cycle (cycle four)<p>Finally, from the discussion section, they hypothesize that the effect is likely due to the stress of the immune response. Seems reasonable; would be interesting to see if there are similar studies for conventional vaccine tech