Microneedle patches: usability and acceptability for self-vaccination against influenza

Abstract

While therapeutic drugs are routinely self-administered by patients, there is little precedent for self-vaccination. Convenient self-vaccination may expand vaccination coverage and reduce administration costs. Microneedle patches are in development for many vaccines, but no reports exist on usability or acceptability. We hypothesized that naïve patients could apply patches and that self-administered patches would improve stated intent to receive an influenza vaccine. We conducted a randomized, repeated measures study with 91 venue-recruited adults. To simulate vaccination, subjects received placebo microneedle patches given three times by self-administration and once by the investigator, as well as an intramuscular injection of saline. Seventy participants inserted patches with thumb pressure alone and the remainder used snap-based devices that closed shut at a certain force. Usability was assessed by skin staining and acceptability was measured with an adaptive-choice analysis. The best usability was seen with the snap device, with users inserting a median value of 93-96% of microneedles over three repetitions. When a self-administered microneedle patch was offered, intent to vaccinate increased from 44% to 65% (CI: 55-74%). The majority of those intending vaccination would prefer to self-vaccinate: 64% (CI: 51-75%). There were no serious adverse events associated with use of microneedle patches. The findings from this initial study indicate that microneedle patches for self-vaccination against influenza are usable and may lead to improved vaccination coverage.

Keywords: Acceptability; Influenza; Microneedle, Human study; Usability.

Figure 1

A placebo microneedle patch and examples of skin stains applied to evaluate usability. (A) A 12x10 mm microneedle array (arrow) on a 30 mm-diameter foam adhesive patch with a polyacetal liner that protects the microneedles in packaging. (B) The microneedle array under magnification, showing 100 microneedles each measuring 750 μm long. (C) Gentian violet skin stain and (D) fluorescein skin stain labeling sites of microneedle penetration into the skin of human participants.

Figure 2

Design of the snap-based device providing force feedback during microneedle patch administration. (A) Three-dimensional rendering of the device measuring 1.4 cm in diameter and 0.4 cm in height in the closed position. The top portion hinges and closes onto the bottom portion with a snapping noise. Devices were placed on the back of microneedle patches to assist with insertion by providing audible feedback to the user when sufficient force was applied. (B) The force required to close the device (n=10) compared to blinded thumb presses by an experienced investigator estimating the force required for microneedle insertion into skin (n=10). Error bars show standard deviation.

Figure 3

Usability of microneedle patches. (A) Usability for insertion with thumb pressure alone (n=69). (B) Usability with the snap-based device (n=20). The y axis shows the percent of microneedles in a patch that punctured skin, as determined by a skin staining assay. Attempts SA1 through SA3 are participant self-administrations. Best SA is the highest percent administered from the three attempts by a participant. The control is investigator administration. A random jitter was applied to separate overlapping points (±1% on the y-axis).

Figure 4

Acceptability of microneedle patches and self-vaccination assuming patches have similar effectiveness and cost to injections. Participant preference for four vaccination options is shown: i) IM injection, ii) healthcare worker (HCW) applies a patch, iii) self-administration of a patch with a healthcare worker nearby and iv) self-administration of a patch at home. The unfilled portion shows participants who would remain unvaccinated. (A) Microneedle patches without self-vaccination options (i.e., only options (i) and (ii)). (B) Microneedle patches with self-vaccination options (i.e., options (i) through (iv)). (C) Comparison of self-vaccination acceptability for participants who inserted with thumb pressure alone or with the snap-based device. Self-vaccination preference was significantly higher for those using the snap-based device (p = 0.004).