gms | German Medical Science

Background: A significant proportion of people infected with SARS-CoV-2 develops long-term symptoms after the acute phase of COVID-19, known as long or post COVID condition. While it has become clear that COVID-19 vaccines protect effectively against acute severe disease, their effectiveness in preventing post COVID condition is still a matter of research. Several systematic reviews have been conducted, however, there is considerable heterogenicity between these reviews and the body of evidence related to this topic expands rapidly.

Objective: To perform a living systematic review on the efficacy and effectiveness of vaccines against COVID-19, administered before SARS-CoV-2 infection, to prevent a post COVID condition.

Methods: We searched Embase and Medline via OVID, the Long Covid Classification in preVIEW, the COVID-19 L·OVE repository, the Cochrane covid-19 study register and Clinicaltrials.gov on March 20, 2024. We included randomized controlled studies as well as non-randomized intervention studies if they comprised a comparison group. Individuals of all ages and irrespective of sex/gender were included. We considered studies that investigated immunization with at least one dose of a COVID-19 vaccine administered before SARS-CoV-2-infection. Control groups receiving placebo, no vaccination, or a vaccine not directed against COVID-19 were considered. As primary outcome, post COVID condition defined as continuation or development of new symptoms three months after the initial SARS-CoV-2 infection was analysed. Secondary outcomes included various long and post COVID definitions as well as single and multiple long-term symptoms after a SARS-CoV-2 infection. In addition, recovery from post COVID condition measured as time until reconvalescence was investigated, as well as limitations in every day activity and quality of life. We used the GRADE methodology to assess confidence in the estimates. Updates of the search and analysis will be performed every 3 months (until February 2025). The protocol has been registered on the PROSPERO database (CRD42024503890).

Results: We obtained 9458 publications in our search. After de-duplication, 6019 entries remained for title and abstract screening. Of these, 30 studies were included in the primary review. Results of this first review including subgroup- and sensitivity-analyses will be presented.

Discussion and conclusion: As of today, nine systematic reviews on the efficacy and effectiveness of COVID-19 vaccines in preventing post COVID condition have been conducted and came to heterogenous results. Our living systematic review will provide a comprehensive and up-to-date overview on the currently available evidence on this topic. The results will serve as a basis for discussions in relevant advisory groups whether this aspect should be considered in current vaccination strategies.

Funding: This study is funded by the German Federal Ministry of Health.

The authors declare that they have no competing interests.

The authors declare that an ethics committee vote is not required.