You are in good health, you have no risk factors, but the specter of long COVID frightens you and you hope to protect yourself with COVID-19 vaccine boosters?
This strategy would be of little use in lowering your risk of long COVID, suggests a study published in the journal
Clinical Infectious Diseases by a team from the Faculty of Medicine, the CHU de Québec - Université Laval Research Center, and the Institut national de santé publique du Québec.
"There are two ways in which the COVID-19 vaccine can prevent long COVID," emphasizes the study lead, Sara Carazo. "The first, which has been overlooked in many studies, is by reducing the risk of COVID-19 infection. If you don't contract the infection, you cannot have long COVID. The second is by reducing the risk that people who have had COVID-19 develop persistent symptoms. Our study covers both of these components."
The research team studied the question in a group of more than 14,000 healthcare workers in the Quebec network. The period covered by the study was divided into two blocks. The first, from January 3 to December 18, 2021, is the period before the arrival of the Omicron variant. The second, from December 19, 2021, to February 20, 2023, is part of the Omicron period.
The analyses revealed that, during the pre-Omicron period, vaccination reduced the risk of long COVID by 90%. "The first vaccines were very effective at preventing infection and this translated into high protection against long COVID," explains Professor Carazo.
During the Omicron period, among people who had not had COVID-19, vaccination reduced the risk of long COVID by 57%, but this protection decreased rapidly and became practically nil after 6 months. "During this period, the vaccine's effectiveness against COVID-19 was only 41%, whereas it was 95% after 2 doses during the pre-Omicron period. Furthermore, the duration of protection against infection decreased with the arrival of this variant," specifies the researcher.
Finally, the research team found that people who had had COVID-19 and who had been vaccinated at least twice benefited from a reduction of more than 80% in the risk of long COVID. This percentage was not affected by the number of doses received, the variant involved, or the time elapsed since the last vaccination.
"Our results suggest that the first vaccines strongly reduced the risk of long COVID. However, now that the severity of the infection has decreased and a good portion of the population has been vaccinated and has had COVID-19, the risk of severe COVID-19 and long COVID has become low. Receiving a vaccine booster does not seem to provide additional benefits, at least not for people who do not have risk factors," summarizes Professor Carazo.
The signatories of the
study published in
Clinical Infectious Diseases are
Sara Carazo, Jonathan Phimmasone, Katia Giguère, Manale Ouakki, Denis Talbot, Charles-Antoine Guay, Chantal Sauvageau, Nicholas Brousseau, and Gaston De Serres. Danuta Skowronski, from the BC Centre for Disease Control in British Columbia, completes the list.