This is a summary, written by members of the CITF Secretariat, of:

Nayyerabadi M, Fourcade L, Joshi SA, Chandrasekaran P, Chakravarti A, Massé C, Paul ML, Houle J, Boubekeur AM, DuSablon C, Boudreau V, Bovan D, Darbinian E, Coleman EA, Vinci S, Routy JP, Hétu PO, Poudrier J, Falcone EL. Vaccination after developing long COVID: impact on clinical presentation, viral persistence and immune responses. Int J Infect Dis. 2023 Sep 15:S1201-9712(23)00720-8. doi: 10.1016/j.ijid.2023.09.006.

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

A CITF-funded study, published in the International Journal of Infectious Diseases, explored whether COVID-19 vaccination in people with post-COVID-19 condition (PCC), also known as Long COVID, could affect their symptoms, immune responses, and viral persistence. The study found that higher pro-inflammatory responses were associated with Long COVID symptoms, but vaccination helped mitigate symptoms, possibly by decreasing systemic inflammation. Vaccination did not reduce the persistence of viral products left by the virus that could be involved in perpetuating inflammation through non-classical monocytesWhite blood cells that can have pro-inflammatory behaviour and secrete inflammatory cytokines in response to infection.. This study was led by Dr. Emilia Liana Falcone, Center for Immunity, Inflammation and Infectious Diseases, Montreal Clinical Research Institute (IRCM) and Université de Montréal.

83 participants who had previously experienced SARS-CoV-2 infection and who had been diagnosed with PCC or “Long COVID” (according to the WHO clinical case definition) were recruited for this study. Participants were between 18 and 100 years old, and were either self-referred or referred by a healthcare provider between February 12th and September 8th, 2021. Among the 83, 44 had not yet received a vaccine at the first study visit. They were compared to those who had received 1 or 2 doses and the responses to vaccination for 39 of them were assessed.

Key findings:

  • Participants were asked about the presence of 49 symptoms/signs associated with Long COVID at each study visit. The top five symptoms reported were: fatigue (81.9%), concentration issues (47.0%), memory issues (39.8%), headaches (32.5%), and shortness of breath at rest (31.3%).
  • COVID-19 vaccination reduced the number of symptoms in participants and led to significantly fewer organ systems being affected. Long COVID symptoms did not lessen as much in people who had not yet been vaccinated.
  • Overall, over time among the 83 participants, 77.8% reported improved, 7.4% worsened, and 14.8% unchanged well-being scores. Correspondingly, 86% reported fewer, 8.3% more, and 5.6% the same number of PCC symptoms.
  • COVID-19 vaccination after Long COVID symptoms was associated with better well-being scores and reduced systemic markers of inflammation. Those who received two vaccine doses (vs. none or one) saw decreased Long COVID symptoms and lower inflammation markers (plasma cytokine/chemokine levels).
  • COVID-19 vaccination after Long COVID symptoms reduced but did not stop the persistence of viral products left by the virus. SARS-CoV-2 spike and nucleocapsid proteins were detected in 15 out of 39 participants before vaccination and were detected in 7 of 39 participants after two doses of vaccine.
  • A viral reservoir may persist, even after one or two vaccine doses. SARS-CoV-2 S1 antigens persisted in non-classical monocytes and granulocytes, even among some study participants who were vaccinated.

Of the 44 unvaccinated participants among the 83 participants included in this study, 39 were also evaluated after one (n=23) and/or two (n=16) vaccine doses (longitudinal analysis). The study team also performed a cross-sectional analysis comparing all unvaccinated participants (n=44) with those having received one (n=61) or two vaccine doses (n=39).