Are there clinically significant interactions between COVID-19 vaccination and post-COVID-19 condition (long COVID)?

Abstract

Background: “Long COVID” has been studied both as post-acute sequelae (PAS), defined as symptoms 4 to 12 weeks post diagnosis, and as post-COVID-19 condition (PCC), defined by the World Health Organization as persistent or recurring symptoms lasting for at least 8 weeks and occurring 12 or more weeks after an acute COVID-19 infection. It is important to know if there are any beneficial or harmful effects of COVID-19 vaccination on PAS or PCC, or if PAS or PCC increases the risk of adverse events following vaccination. This report addresses three questions: Does COVID-19 vaccination before or after COVID-19 infection decrease the risk of developing PAS or PCC? Among those who already have PAS or PCC, does COVID-19 vaccination affect their symptoms? Is it safe to receive a COVID-19 vaccine after PAS or PCC? Methods: Twenty databases and key websites were searched for relevant reviews, peer-reviewed publications and preprints up to January 13, 2022. Search terms included the following: immuniz*, immunis*, vaccin*, long covid, long-covid, post covid, post-covid, chronic covid, chronic-covid, long-term sequelae, long hauler and long-hauler. The search netted 97 citations, which were screened for relevance. Data were extracted from relevant studies into three evidence tables to address each of the questions. Results: Fourteen relevant studies were identified: four prospective cohort studies; four retrospective cohort studies; and six cross-sectional studies. One was peer-reviewed, twelve were preprints and one was a letter to the editor. Twelve studies reported on vaccines authorized for use in Canada and are reported on here; the two others were on a vaccine authorized for use in India.