In October 2020, the European Centre for Disease Prevention and Control (ECDC) published the results of a systematic literature review to assess the efficacy, effectiveness and safety of enhanced inactivated flu vaccines (versus standard-dose or placebo) for the prevention of laboratory-confirmed influenza in adults ≥18 years of age.1
Only direct comparisons versus traditional vaccines were considered in the review as indirect comparisons were considered to be typically underpowered to detect differences in effect in this context.1
Methods of the ECDC systematic literature review
A systematic literature review of records published across MEDLINE, Embase, CINAHL and The Cochrane Library, up to 7 February 2020, was conducted. Randomised controlled trials and non-randomised studies of interventions were eligible for inclusion and publications were screened for relevance by two independent reviewers. Where two or more studies reported the same outcomes, results were pooled. Evidence quality was graded using Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology (Figure 1).1
Results of the ECDC systematic literature review for recombinant haemagglutinin vaccines1
Evidence reviewed was the two pivotal Supemtek clinical trials versus standard-dose egg-based quadrivalent flu vaccine.
|“...Studies appear to suggest that recombinant HA vaccines may offer better protection than no vaccination or standard influenza vaccines, with some possible cross-protection to drift variants”||“...Findings of this review suggest that the safety profile of recombinant HA vaccines is largely similar to that of traditional influenza vaccines in terms of local and systemic effects (low-moderate certainty evidence)”||“...Data related to efficacy or effectiveness for recombinant HA vaccines were limited to two efficacy randomised controlled trials”|
*Versus traditional standard-dose quadrivalent influenza vaccination (QIVe) in adults ≥50 years of age.
†Trial 1 Randomised controlled trial to evaluate the protective efficacy of Supemtek (n=4,301) (45 µg of recombinant HA per strain, 180 µg of protein per dose) versus standard-dose egg-based quadrivalent influenza vaccine (QIVe) (n=4,303) (15 µg of HA per strain, 60 µg of protein per dose) during the 2014/15 influenza season. Primary endpoint: relative vaccine efficacy (rVE) against RT-PCR-confirmed, protocol-defined, influenza-like illness caused by any influenza strain starting 14 days or more after vaccination in adults aged 50+ years. The study was designed to demonstrate non-inferiority of Supemtek in terms of rVE. Trial 2: Observer-blind, randomised, active-controlled trial to evaluate immunogenicity of Supemtek (n=998) versus standard-dose QIVe (n=332) during the 2014/15 influenza season. Co-primary endpoints: non-inferiority of HA inhibition (HAI) seroconversion rates (SCRs) and post-vaccination geometric mean titre (GMT) ratios for each antigen in ambulatory, medically stable adults 18–49 years of age.2,3
- ECDC (2020) Systematic review of the efficacy, effectiveness, and safety of newer and enhanced seasonal influenza vaccines for the prevention of laboratory-confirmed influenza in individuals aged 18 years and over. https://www.ecdc.europa.eu/sites/default/files/documents/seasonal-influenza-vaccines-systematic-review-efficacy.pdf (Accessed May 2023).
- Dunkle LM, et al. N Engl J Med. 2017;376(25):247–37.
- Dunkle LM, et al. J Infect Dis. 2017;216(10):1219–1226.
ECDC, European Centre for Disease Prevention and Control; GMT, geometric mean titre; GRADE, Grading of Recommendations Assessment, Development and Evaluation; HAI, hemagglutinin antigen; HA, haemagglutinin antigen inhibition; QIVe, egg-based quadrivalent influenza vaccine; RT-PCR, reverse-transcriptase polymerase chain reaction; rVE, relative vaccine efficacy; SCR, seroconversion rate; WHO, World Health Organization.
Date of preparation: May 2023