Data Show Changes in Vaccine Trials During COVID-19 Pandemic


Study results indicate a decrease in the exclusion of older adults but no significant change for individuals who are immunocompromised.

During the COVID-19 pandemic, there was a decrease in the exclusion of older adults in vaccine trials, but there was no significant change in the inclusion of individuals who are immunocompromised, according to the results of a study published in Aging Clinical and Experimental Research.

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Investigators wanted to observe whether the rates of immunocompromised and older individuals, who are often excluded from vaccine trials, decreased over time during the pandemic.

They used the search engines from the European Medicines Agency and FDA to identify all vaccines approved against COVID-19, influenza, and pneumococcal disease between 2011 and 2021. Investigators screened the study protocols for direct and indirect age exclusion criteria and exclusion of individuals who were immunocompromised.

They also reviewed study with no explicit exclusion criteria and investigated the actual inclusion of immunocompromised individuals.

There were 2024 trial records found, but just 322 were eligible for this review. Among the 193 influenza and pneumococcal vaccine trials, 81 had an explicit age exclusion, and 150 had an indirect age-related exclusion.

In the influenza and pneumococcal trial, approximately participants 42% had direct age-related exclusion criteria, and 78% had indirect age-related inclusion.

In total, approximately 84% of the trials were likely to exclude older individuals.

The most common indirect age-related exclusion criterion were non-specific concerns, followed by concerns about compliance, cognitive impairment, comorbidities, and access to technology or digital platforms.

There was a 18% decrease in the proportion of trials with age-related exclusion between 2011 and 2021 for the influenza and pneumococcal trials and 2020 and 2021 for the COVID-19 vaccine trials.

Among the COVID-19 trials, approximately 26% had direct age exclusion. and 64% had indirect exclusion, with 66% likely to exclude older adults.

The most common indirect age-related exclusion criteria were also non-specific concerns, followed by cognitive impairments, compliance, comorbidities, physical impairments, and access to digital or technology platforms.

Approximately 66% of both exclusion criteria were likely to exclude older individuals.

Investigators used a sub-analysis observational and randomized trials and found a decrease of 25% and 9%, respectively. For individuals who were immunocompromised, 45% of the influenza and pneumococcal vaccine trials compared with 42% of the COVID-19 vaccine trials.

Among the studies, 74 did not explicitly exclude older individuals. However, 74% did not explicitly report subgroup outcomes for individuals older than aged 65 years.

For the 94 trials that did not exclude immunosuppression, 54% did not have outcomes specific to those who were immunocompromised.

Approximately 35% of the 94 trials included some or all the individuals who were immunocompromised. Nine of the 94 trials did not include individuals who were immunocompromised.

Study limitations included that a detailed review of every trial protocol in detail was not conducted for trials with no explicit exclusion criteria, according to investigators.


Bukan K, Pearce-Slade T, Eiberg M, Tinelli M, et al. Exclusion of older adults and immunocompromised individuals in influenza, pneumococcal and COVID-19 vaccine trials before and after the COVID-19 pandemic. Aging Clin Exp Res. doi: 10.1007/s40520-023-02380-4

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