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Clinical Assessment of Vaccine Safety Pre-licensure I

This article outlines the the process of the first stage in assessing vaccine safety, Phase I, before introducing adverse events (AEs).

After animal studies, clinical trials in humans begin in a stepwise fashion.

The ’first-in-man’ clinical trial is a Phase 1 study where the new vaccine is administered to healthy volunteers for the first time. The new vaccine is given sequentially to subjects with an appropriate period of observation between dosing to exclude any immediate, severe side effects of concern before participants are dosed.

Infographic showing how a Phase 1 study works. The first volunteer is vaccinated. If the review is an acceptable safety profile, then more volunteers can be vaccinated and the results reviewed. If the review gives a safety concern, no further participants are enrolled.

If you need a text version of the image above, this is available as a PDF.

The risks of not following a staggered enrolment design were demonstrated in a ‘first-in-man’ trials of six study participants who received a new immunotherapy drug (TGN1412) at the same time and became immediately, extremely unwell (you can read more about this example via this link).

Detailed information is actively collected from participants in Phase 1 trials, often via diaries, to gain information on all the side effects participants experience post-vaccination. These side effects are known as “adverse events” (AEs). ‘Safety’ blood tests are also performed to look for any adverse effects of the vaccine on bone marrow, liver or kidney function. All adverse events are collected and assessed as to whether they are deemed to be related to the vaccine or not.

In the next step we will take a closer look at adverse events and the assessment of vaccine safety.