HUMAN RABIES VACCINES
Vaccination has been an integral part of rabies prevention since
1885 when Pasteur first successfully immunized a 9-year old boy
bitten by a rabid dog. Until two decades ago, however, the human
vaccines in use had relatively low purity and potency. A difficult
vaccination schedule of 14-21 inoculations with two booster doses
was required for post-exposure treatments. In addition, adverse
reactions during vaccination were common. Since 1980, cell
culture-derived vaccines with greater immunogenicity have been used
in this country. These vaccines have proved to be safe and
effective when administered correctly.
Currently Available Vaccines:
Three human rabies vaccines are currently available in the United
States: human diploid cell vaccine (HDCV); rabies vaccine
adsorbed (RVA); and as of late 1997, purified chick embryo
cell culture vaccine (PCECV). All three vaccines can be given
before an exposure occurs (preexposure vaccination), as well as
after a person is bitten or otherwise exposed to a rabid animal
(postexposure vaccination).
Interchangeability of Vaccines:
Whenever possible, the vaccine from a single manufacturer should be
used to complete a series; however, HDCV and RVA are
interchangeable when used as recommended. Although the experience
with PCECV is more limited, booster doses of this vaccine appear to
elicit a satisfactory immune response in persons previously
vaccinated with HDCV. In addition, persons immunized with duck
embryo vaccine respond appropriately to booster doses of HDCV and
RVA.
Adverse Effects of Rabies Vaccines:
HDCV: Anaphylactic reactions have been reported but appear
to be very rare. Local reactions (pain, redness, swelling, or
itching) are reported by 25% of HDCV recipients. Mild systemic
symptoms occur in about 20% of recipients. An immune complex-like
reaction (characterized by urticaria, and sometimes including
arthralgia, arthritis, angioedema, nausea, vomiting, fever, and
malaise) occurs in approximately 6% of persons receiving
booster doses of HDCV. This reaction is much less common
in persons undergoing primary immunization. In no cases have
the illnesses been life-threatening. Three cases of a
post-vaccination transient illness resembling Guillain-Barre
syndrome have been reported. All three resolved without sequelae.
RVA: Anaphylactic reactions have not been reported. Local
reactions occur in 65-70% of RVA recipients. Up to 10% of
recipients report mild systemic symptoms. Fewer than 1% develop an
immune complex-like illness. No serious neurologic conditions have
been reported following RVA administration. PCECV: PCECV has
been used extensively in other countries. Approximately 11.8
million doses have been distributed worldwide. Two instances of
anaphylaxis have been reported. PCECV is derived from eggs and
should not be administered to people with egg allergies. Local and
mild systemic reactions appear to be less common than with HDCV. No
immune complex-like illnesses have been reported. Serious
neurologic complications have been reported in 21 recipients of
this vaccine.
Use in pregnancy: Although animal reproductive studies
have not been conducted with these vaccines, no fetal abnormalities
have been attributed to use of HDCV, RVA, or PCECV. If vaccine is
indicated during pregnancy, it should be given.
Drug Interactions: Immunosuppressive agents
(including corticosteroids) can interfere with the development of
antibodies following vaccination and should not be administered
during postexposure therapy unless essential for the treatment of
other conditions. Antimalarials (such as chloroquine
phosphate and mefloquine) can also interfere somewhat with the
response to rabies vaccines. Vaccine should only be administered by
the IM route in persons receiving these drugs.
When to Check Postvaccination Titers: Persons who may be
immunosuppressed (either by disease or medications) should have
postvaccination antibody titers checked to determine if adequate
protection has developed. The standard test is the Rapid Fluorescent
Focus Inhibition Test (RFFIT), which is currently done routinely at
several laboratories. Each laboratory will
provide details on how to collect and submit specimens. For questions
about emergency serologic testing, contact the Communicable Disease
Epidemiology Section at (206) 361-2914 or toll-free at 1-877-539-4344.
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