Fig. 2: Association between COVID-19 vaccine timing/doses and long COVID symptoms and quality of life (QoL) outcomes.

Association between timing and number of COVID-19 vaccine doses with long COVID and quality of life (QoL) outcomes. Crude—(vaccinated after-(n = 380), 1-dose—(n = 123), 2-doses—(n = 215), 3 or more doses—(n = 311)). Adjusted—(vaccinated after—(n = 196), 1-dose—(n = 62), 2-doses—(n = 96), 3 or more doses—(n = 144)). a Shows the odds ratios (ORs) of reporting long COVID symptoms across vaccination groups compared to an unvaccinated reference group (not shown). Black points represent crude ORs and red points represent adjusted ORs, both with 95% confidence intervals. Individuals vaccinated with two or more doses prior to infection had lower odds of reporting long COVID symptoms compared to those unvaccinated. A dose–response pattern was observed, with the lowest odds among those who received three doses before infection. b Represents the estimated adjusted mean changes in EQ-5D QoL scores among individuals who reported post-COVID condition, stratified by vaccination status. Bar heights represent the adjusted mean change in QoL compared to the unvaccinated, with error bars indicating 95% confidence intervals. Asterisks above bars indicate pairwise statistical comparisons using p values (*p < 0.05; **p < 0.01). Individuals vaccinated with two or three doses before infection reported significantly better QoL than those vaccinated after infection or with only one dose. c Represents the estimated adjusted change in QoL scores for the entire cohort, regardless of symptom presence. Again, vaccination prior to infection (especially with two or more doses) was associated with significantly improved QoL outcomes. p Values indicate significance levels for each group compared to the unvaccinated group.