The purpose of this study is to determine immunogenicity and safety of intradermal administration of the PCEC rabies vaccine in adults.

Approximately 16,000-39,000 persons come in contact with potentially rabid animals and receive rabies postexposure prophylaxis (PEP) each year in the US. To appropriately manage potential human exposures to rabies, the risk for infection must be accurately assessed. Administration of rabies PEP is a medical urgency, not a medical emergency, but decisions must not be delayed. Prophylaxis is occasionally complicated by adverse reactions, but these reactions are rarely severe. Current data on the safety and efficacy of active and passive rabies vaccination were derived from both human and animal studies. Timely and appropriate human pre-exposure prophylaxis (Pre-EP) and PEP will prevent human rabies. Currently in the US, the approved dosage and administration for PEP in previously unvaccinated persons consists of the administration of vaccine (HDCV or PCECV) and HRIG. Vaccine is administered IM on days 0, 3, 7, 21, and 28 (deltoid area). The approved dosage and administration for pre-exposure prophylaxis (Pre-EP) consists of three 1.0-mL injections of vaccine (HDCV or PCECV) administered IM (deltoid area), one injection per day on days 0, 7, and 21 or 28). Intradermal (ID) route of administration of rabies vaccination is used in certain countries both for PEP and Pre-EP, and approved by WHO for modern potent cell culture vaccines. Recent studies outside the USA found the use of PCEC rabies vaccine by ID administration immunogenic and safe.

The primary goals of this study are to obtain additional safety and immunogenicity data on ID administration of 0.1 mL doses of the inactivated PCEC rabies virus vaccine in adults. Given the need to provide alternative routes of administration to the current approved intramuscular route in order to protect a larger number of people facing potential vaccine shortages. The data yielded by this clinical trial will provide evidence to support alternative route of administration and dose of PCECV in the US.

Inclusion Criteria:

1. Laboratory personnel, epidemiologists, EISOs, veterinary students, interns, and other first responders at CDC; other CDC employees; and healthy volunteer adults. Persons who contact the study coordinator will be assessed for possible occupational exposure to rabies using the risk assessment form (appendix E). The volunteers reporting occupational exposure will be selected to enter the study.
2. Male or nonpregnant females (as indicated by a negative urine pregnancy test prior to first dose of vaccine), aged 18 years and older.
3. Women of childbearing potential who are at risk of becoming pregnant must agree to practice adequate contraception (i.e., barrier method, abstinence, or licensed hormonal methods) for the entire study period.
4. Be in good health, as determined by vital signs (pulse, blood pressure, oral temperature), medical history, and a targeted physical examination based on medical history.
5. Able to understand and comply with planned study procedures.
6. Provide informed consent prior to any study procedures and be available for all study visits.
7. Have health insurance.

Exclusion Criteria:

1. Have a known allergy to PCECV.
2. Have a known allergy or sensitivity to eggs or latex (in the stopper).
3. Have a positive urine pregnancy test prior to first vaccine dose (female of childbearing potential age).
4. Are immunosuppressed as a result of an underlying illness or treatment.
5. Have active neoplastic disease or a history of any hematologic malignancy.
6. Are using oral or parenteral steroids, high-dose inhaled steroids (>800 μg/day of beclomethasone dipropionate or equivalent) or other immunosuppressive or cytotoxic drugs.
7. Have a history of receiving immunoglobulin or other blood product within the 3 months prior to enrollment in this study.
8. Have an acute illness that is accompanied by an oral temperature greater than 100.4°F, within 1 week of vaccination.
9. Received an experimental agent (vaccine, drug, biologic, device, blood product, or medication) within 1 month prior to enrollment in this study, or expects to receive an experimental agent during the 1st month of the study period.
10. Have any condition that would, in the opinion of the site investigator, place the subject at an unacceptable risk of injury or render the subject unable to meet the requirements of the protocol.
11. He/she is a CDC worker under direct supervision of any of the primary study investigators (Dr. Sergio Recuenco, and Dr. Eli Warnock).

Baseline characteristics are reported for all enrolled participants (N=130).

From vaccination through final study follow-up, approximately 6 months

Adverse events were assessed after vaccination and during follow-up visits. Participants recorded systemic and local adverse events for 7 days after vaccination.

This was a single-center, open-label, non-randomized study conducted in healthy adult CDC employees. The sample size was limited and may not detect rare adverse events. Children, pregnant women, immunocompromised persons, and persons with significant underlying illness were excluded, limiting generalizability.