Abstract
Dear Editor,
We would like to respond to the Letter to the Editor to our study titled “Effect of COVID vaccination on monthly migraine days: A longitudinal cohort study” (1) and the concerns raised by Daungsupawong and Wiwanitkit (2). They raise concern regarding the sample size employed in our study. In our published article, we argued that our sample size was adequate for the vaccine analysis. We took stringent measures, including enforcing an E-diary compliance threshold of ≥80% per month, to ensure the robustness and dependability of our findings (3). This exceptionally high compliance rate enabled us to precisely track shifts in migraine frequency and medication utilization in the context of COVID-19 vaccination. Nonetheless, we acknowledged already in the discussion section of our paper that this factor resulted in lesser inclusions in the infection analysis, which may account for our inability to identify changes in monthly migraine days (MMD) and monthly headache days (MHD) due to COVID infection.
Regarding concerns about self-reported data of the infection- and vaccination dates, Daungsupawong and Wiwanitkit highlight the potential for recollection bias and reporting errors in general. As discussed in our article, it is true that the exact day and method of diagnosing COVID-19 infection could vary among participants, potentially affecting the accuracy of infection date estimation. However, this potential limitation was partly mitigated by our data analysis which was comparing a month rather than a few days after infection. Importantly, the vaccination analysis benefited from participants easily accessing their exact vaccination dates and types through the “Corona check” app/website developed by the Dutch Ministry of Public Health, Welfare, and Sport, ensuring high accuracy.
In response to the comment suggesting that medication adjustments were not considered, we respectfully disagree. As outlined in the methodology section, the study did take medication adjustments into account by incorporating them as a covariate in the linear mixed model analyses, even though the primary focus was on the alteration in monthly migraine days (MMD). We acknowledge a true limitation of our study, namely assessing disability with other validated questionnaires (e.g. HIT-6 or MIDAS). Integrating such instruments might have enriched the evaluation by providing an even more comprehensive understanding of the subject matter.
Finally, it was suggested that there is a need for larger sample sizes and multicenter data to conduct in-depth epidemiological studies on the connections between illness and immunization. We agree that this may provide even more robust insights into the relationships between COVID-19 and migraine. Such studies would allow us to delve deeper into potential mechanisms and variability in immune responses based on genetic traits, which is an exciting avenue for future research. We would, therefore, applaud if more centers would incorporate our validated E-headache diary tool to work together if unexpected triggers for migraine may occur in the future.
In conclusion, we appreciate the comments, these discussions are essential for advancing scientific knowledge. While our study has some limitations, it offers valuable insights into the potential effects of COVID-19 infection and vaccination on migraine patients. We encourage further research to expand on these findings and explore the complex interplay between inflammatory mediators and migraine, and individual genetic factors.
