Thermostability of Measles and Rubella Vaccines in a Microneedle Patch.

Measles and rubella vaccinations are highly effective at reducing disease prevalence; however, logistic issues related to subcutaneous administration and vaccine wastage limit the extent of vaccination coverage. Microneedle (MN) patches can increase coverage by easing logistics through simplified administration and improved stability. This study demonstrates the thermostability of a bivalent measles and rubella vaccine MN patch. Rubella vaccine stability required pH buffering during drying; potassium phosphate buffer at neutral pH was optimal for both vaccines. Screening 43 excipients for their ability to retain potency during drying and storage yielded sucrose-threonine-potassium phosphate buffer formulation at pH 7.5 as an optimal formulation. MN patches made with this formulation had no significant loss of vaccine titer after one month and remained within a one log10 titer loss cutoff after 3 - 4 months at 5°C, 25°C and 40°C. Finally, these patches were shown to be immunogenic in juvenile rhesus macaques. This work demonstrates the potential for MN patches for measles and rubella vaccination to be removed from the cold chain, which is expected to decrease vaccine cost and wastage, and increase vaccination coverage.

Extended delivery of vaccines to the skin improves immune responses.

Vaccines prevent 2-3 million childhood deaths annually; however, low vaccine efficacy and the resulting need for booster doses create gaps in immunization coverage. In this translational study, we explore the benefits of extended release of licensed vaccine antigens into skin to increase immune responses after a single dose in order to design improved vaccine delivery systems. By administering daily intradermal injections of inactivated polio vaccine according to six different delivery profiles, zeroth-order release over 28 days resulted in neutralizing antibody titers equivalent to two bolus vaccinations administered one month apart. Vaccinations following this profile also improved immune responses to tetanus toxoid and subunit influenza vaccine but not a live-attenuated viral vaccine, measles vaccine. Finally, using subunit influenza vaccine, we demonstrated that daily vaccination by microneedle patch induced a potent, balanced humoral immunity with an increased memory response compared to bolus vaccination. We conclude that extended presentation of antigen in skin via intradermal injection or microneedle patch can enhance immune responses and reduce the number of vaccine doses, thereby enabling increased vaccination efficacy.

A Microneedle Patch for Measles and Rubella Vaccination Is Immunogenic and Protective in Infant Rhesus Macaques.

Background: New methods to increase measles and rubella (MR) vaccination coverage are needed to achieve global and regional MR elimination goals. Methods: Here, we developed microneedle (MN) patches designed to administer MR vaccine by minimally trained personnel, leave no biohazardous sharps waste, remove the need for vaccine reconstitution, and provide thermostability outside the cold chain. This study evaluated the immunogenicity of MN patches delivering MR vaccine to infant rhesus macaques. Results: Protective titers of measles neutralizing antibodies (>120 mIU/mL) were detected in 100% of macaques in the MN group and 75% of macaques in the subcutaneous (SC) injection group. Rubella neutralizing antibody titers were >10 IU/mL for all groups. All macaques in the MN group were protected from challenge with wild-type measles virus, whereas 75% were protected in the SC group. However, vaccination by the MN or SC route was unable to generate protective immune responses to measles in infant macaques pretreated with measles immunoglobulin to simulate maternal antibody. Conclusions: These results show, for the first time, that MR vaccine delivered by MN patch generated protective titers of neutralizing antibodies to both measles and rubella in infant rhesus macaques and afforded complete protection from measles virus challenge.

A microneedle patch containing measles vaccine is immunogenic in non-human primates.

Very high vaccination coverage is required to eliminate measles, but achieving high coverage can be constrained by the logistical challenges associated with subcutaneous injection. To simplify the logistics of vaccine delivery, a patch containing micron-scale polymeric needles was formulated to encapsulate the standard dose of measles vaccine (1000 TCID50) and the immunogenicity of the microneedle patch was compared with subcutaneous injection in rhesus macaques. The microneedle patch was administered without reconstitution with diluent, dissolved in skin within 10 min, and caused only mild, transient skin erythema. Both groups of rhesus macaques generated neutralizing antibody responses to measles that were consistent with protection and the neutralizing antibody titers were equivalent. In addition, the microneedle patches maintained an acceptable level of potency after storage at elevated temperature suggesting improved thermostability compared to standard lyophilized vaccine. In conclusion, a measles microneedle patch vaccine was immunogenic in non-human primates, and this approach offers a promising delivery method that could help increase vaccination coverage.

Measles vaccination using a microneedle patch.

Measles vaccination programs would benefit from delivery methods that decrease cost, simplify logistics, and increase safety. Conventional subcutaneous injection is limited by the need for skilled healthcare professionals to reconstitute and administer injections, and by the need for safe needle handling and disposal to reduce the risk of disease transmission through needle re-use and needlestick injury. Microneedles are micron-scale, solid needles coated with a dry formulation of vaccine that dissolves in the skin within minutes after patch application. By avoiding the use of hypodermic needles, vaccination using a microneedle patch could be carried out by minimally trained personnel with reduced risk of blood-borne disease transmission. The goal of this study was to evaluate measles vaccination using a microneedle patch to address some of the limitations of subcutaneous injection. Viability of vaccine virus dried onto a microneedle patch was stabilized by incorporation of the sugar, trehalose, and loss of viral titer was less than 1 log10(TCID50) after storage for at least 30 days at room temperature. Microneedle patches were then used to immunize cotton rats with the Edmonston-Zagreb measles vaccine strain. Vaccination using microneedles at doses equaling the standard human dose or one-fifth the human dose generated neutralizing antibody levels equivalent to those of a subcutaneous immunization at the same dose. These results show that measles vaccine can be stabilized on microneedles and that vaccine efficiently reconstitutes in vivo to generate a neutralizing antibody response equivalent to that generated by subcutaneous injection.

Alternatives to retroorbital blood collection in hispid cotton rats (Sigmodon hispidus).

Cotton rats (Sigmodon hispidus) are a valuable animal model for many human viral diseases, including polio virus, measles virus, respiratory syncytial virus, and herpes simplex virus. Although cotton rats have been used in research since 1939, few publications address handling and sampling techniques for this species, and the retroorbital sinus remains the recommended blood sampling site. Here we assessed blood sampling methods that are currently used in other species and a novel subzygomatic sampling site for their use in S. hispidus. The subzygomatic approach accesses a venous sinus that possibly is unique to this species and that lies just below the zygomatic arch of the maxilla and deep to the masseter muscle. We report that both the novel subzygomatic approach and the sublingual vein method can be used effectively in cotton rats.