Underrepresentation of older adults in clinical trials on COVID-19 vaccines: A systematic review

During the COVID-19 pandemic older subjects have been disproportionately affected by the disease. Vaccination is a fundamental intervention to prevent the negative consequences of COVID-19, but it is not known if the needs and vulnerabilities of older people are adequately addressed by their inclusion in randomized clinical trials (RCTs) evaluating the efficacy of vaccines for COVID-19. Given this background, we aimed to evaluate if current and ongoing phase II-III RCTs evaluating the efficacy of COVID-19 vaccines included a representative sample of older people. A systematic literature search in PubMed and Clinicaltrials.gov was performed until May 01st, 2021. Among 474 abstracts initially retrieved, 20 RCTs (ten already published, ten ongoing) were included. In the ten studies already published, the mean age of participants was 45.2 ± 11.9 years and only 9.83% of the participants were more than 65 years, 1.66% more than 75 years and less than 1% (0.55%) more than 85 years. In the ten ongoing RCTs, many of the studies aimed at including participants older than 18 years, with one study including participants between 18 and 84 years, and two between 21 and 100 years. In conclusion, our systematic review demonstrates that in published and ongoing phase II-III randomized clinical trials evaluating the efficacy of COVID-19 vaccines only a tiny fraction of the most vulnerable group of older people was included, although they clearly were the first population that had to be vaccinated.