Postwar Vaccine Development Abroad
The most problematic adverse reaction to the inoculation of dogs with attenuated vaccines was inoculation-induced fixed poison rabies, in which rabies is caused by the rabies poison contained in the vaccine. Post-injection paralysis, which is believed to be caused by the nerve substance contained in the vaccine, had also been confirmed. In the U.S., as of 1925, 1/62 of inoculated dogs had developed fixed poison disease; in Australia, as of 1938, 0.20-0.25% of inoculated dogs were paralyzed; and in Japan, as of 1951, 0.006-0.080% of approximately 1 million inoculated dogs had been reported to have been paralyzed.
Around 1939, in the U.S., vaccines for dogs were restricted to dead or non-toxic pathogens that did not contain live toxins, mainly coal acid or chloroform deadly poison vaccines, in order to reduce the number of adverse reactions that could occur.
Even for attenuated vaccines for humans, the occurrence of inoculation incidental lesions was recognized as unavoidable, and the rate was reported to be about 0.08%. There were also many cases where inoculation was ineffective; for example, rabies occurred in one out of 78 patients with head bites, even after vaccination with the Pasteur vaccine. Another problem was that the Pasteur vaccine is a mixture of inactivated and live viruses, which makes it difficult to store for long periods of time.
Coal acid (phenol) vaccine
Fermi, Semple showed that the addition of phenol to an emulsion of fixed venom rabbit brain could partially or completely inactivate the live virus in the Pasteur vaccine.
In 1908, Fermi added 1% phenol to a 10% emulsion of fixed-toxin rabbit brain, sensitized and detoxified it for 1-10 days, and recommended three subcutaneous injections as prophylaxis for dogs. Baves argued that this vaccine was not at all nontoxic, but was a reduced dose solution since intracerebroventricular inoculation still proved toxic, and recommended its use in combination with a serum.
The Fermi method was improved, and a 25% emulsion was made from a 60% glycerin solution with 1% phenol, sensitized at 18-20°C for 24 hours to render it nontoxic, and then diluted 3 times with salt water to make a vaccine, which was widely used in Italy. For canine prophylaxis, 5 to 15 cc of the vaccine had to be injected subcutaneously.
In 1911, Semple developed a vaccine for humans bitten by rabid dogs in India: an 8% fixed poison emulsion with 1% phenol was sensitized at 37°C for 24 hours to render it nontoxic, and then diluted three times with saline solution to make a vaccine. This method served as the basis for the U.S. coal acid inactivated vaccine for human use.
On the other hand, phenol distorts the protein structure and destroys the antigenicity of the rabies virus.
Myelin free vaccine
Conventional vaccines made from adult mammalian neural tissue have caused myelin sensitization, allergic encephalomyelitis, and demyelinating lesions in the central nervous system as side effects. In 1931, Ernest W. W. Harris, Jr.
In 1931, Ernest W. Goodpasture developed a chicken embryo-based rabies vaccine, which was tested in humans from the 1950s through the 1960s, but was ultimately withdrawn because of unreliable efficacy. A duck embryo-derived rabies vaccine was also developed in the 1950s.
Cell-culture vaccine
The “cell-culture vaccine,” in which the virus is inoculated into animal cells, cultured, inactivated, and purified to make a vaccine, was first put to practical use in the development of the polio vaccine. This was followed by research on virus culture using cell culture in the development of rabies vaccines.
1968：PHKCV (hamster kidney cell vaccine) using fixed strain CL-60 (derived from Street Alabama Dufferin rabies virus isolate) approved @ Canada
1971：PHKCV (hamster kidney cell vaccine) using Vnukovo-32 strain (derived from SAD after primary cell adaptation in hamster kidney) was produced in the former Soviet Union.
1974：Bovine kidney fetal cell rabies vaccine using the Pasteur Virus (PV) was developed and approved in the Netherlands.
WHO approved the Human Diploid Cell vaccine (HDCV) using the human diploid cell line WI-38 because of its low side effects.
1978：Canine kidney cell rabies vaccine using Pitman-Moore strain (PM) developed and approved in the Netherlands.
1980：PHKCV lyophilized on aluminum phosphate was approved in China.
1985：Purified Vero cell rabies vaccine (PVRV) was approved using Vero cells established from African green monkey kidney cells.
Postwar Approved Vaccines in Japan
Transition in Human Immunization Products
As for vaccines for humans, diluted attenuated/dried attenuated vaccines using Pasteur-derived or Japanese-derived strains were produced before and immediately after the war; trials were conducted under the guidance of the GHQ to shift to inactivated vaccines. Eventually, the parties concerned reached a consensus, and in April 1952, the vaccine was simultaneously switched to the Semple-type inactivated vaccine by inactivation of brain emulsion from sheep and other animals inoculated with the Nishigahara strain, which was also a rabies strain for animals.
Meanwhile, the enforcement of the Rabies Prevention Law in 1950 during the same period led to a decrease in the number of rabies cases, and after an outbreak in humans in 1956 and an outbreak in animals (cats) in the following year, the disease has remained clean to the present day. The absence of rabies outbreaks led to arguments against vaccination against high doses of non-transparent vaccine (containing 20% brain tissue) and adverse reactions.
In 1971, the vaccine for humans was changed to one using mouse brain emulsion, and in 1980, a dried tissue inactivated culture vaccine was put into practical use, which has been used to this day.
Current human immunization products (2023)
The rabies vaccine for humans in Japan is a purified chick embryo cell vaccine (PCECV), which is divided into pre-exposure vaccination and post-exposure vaccination according to its intended use.
Pre-exposure vaccination refers to vaccination before a person is bitten by a dog or other animal and becomes infected with rabies. It is recommended that people traveling to rabies-endemic areas or staying for a long period of time in areas where contact with animals is unavoidable or where there are no medical facilities nearby be vaccinated prior to travel. Post-exposure vaccination refers to vaccination to prevent the onset of rabies when a person may have been bitten by a dog or other animal in an area where rabies occurs. Vaccination should be initiated as soon as possible after a dog or bat bite (exposure). There are two vaccines approved as drugs in Japan.
● KM Biologics K.K. “Tissue Culture Inactivated Rabies Vaccine”
Rabies virus (HEP Flury strain) acclimated to chicken embryo primary culture cells was grown in chicken embryo primary culture cells of developing chicken eggs collected from chicken flocks not infected with contagious diseases (SPF chickens), and the resulting virus was inactivated with 0.02 vol% beta-propiolactone, concentrated and purified, added a stabilizer, dispensed, and freeze-dried. The product is then concentrated, purified, dispensed with a stabilizer, and lyophilized.
The pre-exposure vaccination consists of two subcutaneous injections of 1.0 mL at 4-week intervals, followed by an additional 1.0 mL dose 6~12 months later. Therefore, vaccination should be started approximately 6 months prior to travel. For post-exposure vaccination, a single dose of 1.0 mL should be injected subcutaneously 6 times, with the first dose on day 0, and subsequent injections on days 3, 7, 14, 30, and 90.
● GlaxoSmithKline K.K. “Rabipur for intramuscular injection“
Rabies virus (Flury LEP strain) is grown in chick embryo primary culture cells, and the resulting virus is inactivated with propiolactone, concentrated and purified, filled with a stabilizer, and lyophilized.
For pre-exposure vaccination, 1.0 mL is administered intramuscularly three times at appropriate intervals (0, 7, 21 days or 0, 7, 28 days). Therefore, vaccination should be started approximately one month prior to travel. For post-exposure vaccination, a single dose of 1.0 mL is administered intramuscularly 4 to 6 times at appropriate intervals. The recommended dates of inoculation are as follows.
Transition in Animal Immunization Products
As for vaccines for animals, the Semple-type inactivated vaccine using goat brain emulsion inoculated with the Nishigahara strain was put into practical use in 1951, but there was a risk of serious side effects, such as allergies derived from goat brain tissue in the vaccine.
In response to concerns about vaccine side effects in the 1950s and the trend toward eliminating the need for vaccination, animal vaccines shifted to inactivated vaccines made from purified goat/mouse brain emulsion beginning in 1978. The protein nitrogen content of the purified vaccine was reduced to less than 200 μg/mL, less than one-tenth of the conventional level, successfully reducing side effects.
The method of vaccination at this time was to inject one dose of 2 mL every 6 months, and in fact, rabies vaccination was required twice a year for dogs.After 1984, the vaccine was shifted to a tissue culture inactivated vaccine, and dogs were vaccinated once a year.
Current animal immunization products (2023)
● Rabies tissue culture inactivated vaccine
The vaccine is a purified and inactivated vaccine made from viral solution obtained by growing rabies cultured cell acclimation virus that meets seed-lot standards in strain-derived cells that meet the same standards.
1mL is injected subcutaneously or intramuscularly in dogs and cats. In Japan, the Rabies Prevention Law established by the Ministry of Health, Labor and Welfare requires all dogs after the age of 3 months to be vaccinated once a year.
