The protective effect of the large-scale use of PHKC rabies vaccine in humans in China.

The protective effect of the large-scale use of PHKC rabies vaccine in humans in China Lin Fangtao' Reported are the results obtained with different immunization schedules of adjuvant or freeze-dried concentrated (FDC) primary hamster kidney cell (PHKC) rabies vaccine on volunteers. The FDC vaccine (potency, 4.5 IU), which was inoculated in six doses, on days 0, 3, 7, 14, 30 and 90, and the adjuvant vaccine (potency 2.5 IU), which was inoculated in five doses, on days 0 and 7 (double dose), 14, 30 and 90, induced earlier, higher, and more persistent neutralizing antibody titres than the adjuvant vaccine which was inoculated in five doses on days 0, 3, 7, 14 and 30. The persistence of the neutralizing antibody titres induced by three intradermal doses of vaccine administered on days 0 (4 sites), 7 (2 sites), and 28 (1 site) was lower than that induced by six intramuscular doses administered on days 0, 3, 7, 14, 30, and 90. A cell-mediated immunity (CMI) was also induced in vaccinees who received the adjuvant vaccine. The protective effect of the adjuvant vaccine was befter than that of the previously used Semple vaccine and has had a positive effect on the epidemiology of human rabies in China. Introduction Because of ethical, economic, and administrative problems, it is not easy to undertake mass immuniza- tion of animals against rabies in many developing countries, including China. Postexposure treatment is, therefore, still a significant means of controlling human rabies, and the economical adjuvant vaccine is well-suited for use among humans in this setting. Both the neutralizing antibody titre and the protective effect of primary hamster kidney cell (PHKC) rabies vaccine (with or without adjuvant) in humans have been determined (1-4), and several years of field trials with both pre- and postexposure inoculation in China indicate that the vaccine is safe and effective. In these trials, 228 volunteers received preexposure inoculation; and 301 patients were given postexposure treatment, most of whom had been bitten by animals with laboratory-proven rabies, while the remainder had been bitten by animals suspected to have rabies and that had escaped. Of the patients, 58 had been bitten by a rabid wolf or feral dog (4, 5). Here we report the neutralizing antibody titres and cell-mediated immunity (CMI) responses in humans vaccinated with different immunization schedules of rabies vaccine. Data are also provided on the protective effect of the adjuvant vaccine used in large-scale postexposure treatment and its effect on the epidemiology of human rabies in China. Wuhan Institute of Biological Products, Ministry of Public Health, 9 Linjlang Road, Wuchung, Wuhan, Hubei, People's Republic of China. Requests for reprints should be sent to this address. Reprint No. 5095 Materials and methods Vaccine Two types of PHKC vaccine (adjuvant and freeze- dried concentrated (FDC)), which were developed from an adapted Beijing strain of a fixed rabies virus grown in primary hamster kidney cells, were employed in the study. The potency of the adjuvant vaccine was determined using the Habel test (index, 100 000) or the NIH test (2.5 IU), and that of the FDC vaccine using the NIH test (2.5 IU). A dose of purified horse immune serum (neutralizing antibody titre=1:2500; WHO Ref- erence Animal Serum, 1:2188) equivalent to 40 IU/kg body weight (0.5ml/kg body weight) was injected simultaneously with the vaccine. Neutralizing antibody titre Samples of sera from vaccinees were taken on days 0, 7, 21, 45 (or 65), 105, and 365, and the neutralizing antibody titre was determined using the method described by Atanasiu (6). The Beijing strain of fixed virus (289-290 passages) or the CVS strain was used as the challenge virus (32-320 LD50). Cell-mediated Immunity Adjuvant vaccine (Lot 83-430; Habel index, 363 160) induced cell-mediated immunity, as indicated by the results of the E-rosette forming and lymphocyte transformation tests (7, 8). Diagnosis Human rabies was diagnosed clinically by physicians in local basic health units located in rural areas and in local country or town hospitals. Bulletin of the World Helth Organization, S (4): 449-454 (1990) © World Health Organization 1990 449 Lin Fangto Vaccinees and observation design (pre-oxposure Immunization) Vacinees. Physicians selected volunteers of both sexes aged 16 years or more who were in good health and who had no previous history of rabies vaccina- tion. The subjects were immunized using several vaccination schedules, doses, and inoculation routes. Every vaccinee was allocated randomly to one of the immunization regimens. Postxposure tatment. Persons bitten by suspected rabid animals were treated by local physicians in the provinces of Jiangshu, Anhui, Juangxi, and Hunan. For mildly exposed persons, vaccine was given on days 0, 3, 7, 14 and 30, and for severely exposed persons, on days 0, 3, 7, 14 and 30, with one or more boosters on day 90 or on days 40, 50, and 120. Retrospective observations Cases of human rabies were reported by physicians in local basic health units to the regional public health units and to the Ministry of Public Health. Results Neutralizing antibody responses with PHKC vaccine The neutralizing antibody responses for the reci- pients of the five-dose or six-dose immunization schedules are shown in Table 1. The adjuvant vaccine (potency 2.5 IU) or FDC vaccine (potency 4.5 IU) induced a good antibody response on day 21 and high level titres on day 45. The responses were more rapid and longer lasting when the adjuvant vaccine was administered on days 0 (double dose) and 7 (double dose), and the FDC vaccine on days 0, 3, 7, 14, 30, and 90. Neutralizing antibody responses with PHKC or PCEC vaccine Two different vaccines-PHKC vaccine (potency, 4.9 IU or 7.3 IU) and purified chick-embryo cell (PCEC) vaccine (potency, 7.5 IU)-were administered intra- muscularly or intradermally. As'shown in Table 2, the neutralizing antibody titres of the PHKC vaccine (potency, 7.3 IU) and PCEC vaccine (potency, 7.5 IU) developed more rapidly and were higher than those of the PHKC vaccine (potency, 4.9 IU). Irrespective of whether PHKC or PCEC vaccine was used, the titres on days 105 and 365 were higher following six intramuscular doses than following three intradermal doses. Cell-mediated Immunity response to the adjuvant PHKC vaccine The cell-mediated immunity response to the adjuvant PHKC vaccine on days 7, 21, 45, 120, and 365 after six doses is shown in Fig. 1. Postexposure protection provided by the adjuvant PHKC vaccine The postexposure treatment schedule for the PHKC vaccine was used on days 0, 3, 7, 14, and 30 for mildly exposed patients, with a booster on day 90, or Table 1: Neutralizing antibody responses of vaccinees given PHKC rabies vaccine (adjuvant or freeze-dried concen- trated) In different Immunization schedules Reciprocal geometric mean titre on days:No. of Vaccine Potency Immunization Study vaccinees lot (IU) schedule (days) 0 7 21 45 105 365 1 17 267' 2.5 0,3,7,14,30 <5 <5 102 (100)b 309 (100) 60.3 (93) 17.2 (50) 30-389C 105-729 10-309 < 10-43 2 14 267 2.5 0,3,7,14,30,90 <5 <5 147.9 (100) 288.4 (100) 457 (100) 20.4 (78.5) 38-810 69-810 50-208 < 10-118 3 14 267 2.5 Ox2, 7x2d <5 0.1 213.8 316 (100) 758.6(100) 21.4(64) 14,30,90 (16) (100) 28-1148 74-4860 < 10-52 < 5-5 74-389 4 16 85-5' 4.5 0,3,7,14,30,90 <5 1.1 363 (100) 630.9 (100) 588.8 (100) 31.6 (87.5) (18.8) 51-1260 69-1862 118- 1219 < 10- 118 <5-7 Adjuvant vaccine Figures in parentheses are the percentage who seroconverted (reciprocal titre >5-10). c Figures in italics are the range.d Double dose. Freeze-dried concentrated vaccine. WHO Bulletin OMS. Vol. 68. 19904s0 Large-scale use of PHKC rabies vaccine In China Table 2: Neutralizing antibody responses of vaccines given PHKC or PCEC rabies vaccine In different Immunization schedules Immunization schedule Reciprocal geometric mean titre on days: No. of Study vaccinees Vaccine Potency and lot (IU) 1 11 PHKC 84-5 2 11 PHKC 84-9 3 5 PCECd ChO14 4 5 PCECd ChO14 5 5 PHKC 84-5 Route8/ Vol. (ml) Days 4.9 im/1.0 0,3,7,14, 28,90 7.3 im/1.0 0,3,7,14, 28,90 7.5 im/1.0 0,3,7,14, 28,90 7.5 id/0.1 0x4' 7x2 28 x 1 4.9 id/0.1 0 x 4 7x2 28 x 1 0 7 21 65 105 365 <5 0.2 (9)b 234 (100) 100 (100) 398 (100) 34 (100) < 5-C 51- 1380 30-617 115-2130 10-209 <5 3 (60) 389 (100) 380 (100) 1148 (100) 132 (100) < 5-5 90-955 51-810 389-2430 43-562 <5 3 (60) 631 (100) 445 (100) < 5-5 209-1862 209-810 <5 2.5 (40) 676 (100) < 5-5 372-1383 <5 1.2 (25) 151 (100) < 5-5 51-324 1698 (100) 178 (100) 465-5012 115-467 468 (100) 129 (100) 240- 1660 51-270 87 (100) 52- 186 224 (100) 96 (100) 24 (100) 30-630 23-224 10-270 ' im = intramuscular; id = intradermal. b Figures in parentheses are the percentage who seroconverted (reciprocal titre: >5-10) c Figures in italics are the range. d Kindly donated by Dr R. Barth. e Four sites. boosters on days 40, 50, and 120 for those who were severely exposed. Over the period 1979-84, we studied retrospectively the protection provided by the PHKC vaccine and compared it with that of the Semple vaccine, which had been used to vaccinate 47 903 persons exposed to rabid or suspectedly rabid animals in the following endemic areas: Jiangshu and Anhui provinces (Table 3) and in Guangxi auto- nomous region and Hunan province (Table 4). The Fig. 1. Cell-mediated Immunity produced by six doses of adjuvant PHKC vaccine In volunteers. Lymphocyte transformation (%) 79 - 77 - * E -rosette 75 -i} Lymphocyte -73- 71- -69- 67 2 7 21 45 120 365 No. of days after initial dose of vaccine data confirmed that the protection provided by adjuvant PHKC vaccine was significantly greater than that induced by the Semple vaccine. The protective effect of the adjuvant vaccine was also studied retrospectively in Hubei province. In 1986-87, 26 cases of human rabies occurred and 389 persons were exposed to rabid or suspectedly rabid dogs; each dog bit 10-30 persons over a 2-day period. Among these individuals, 10 deaths from rabies occurred among 110 patients who had been bitten by one of 9 rabid dogs. Table 5 shows that 9 out of the 10 rabies victims who died had been severely bitten; however, a combination of antiserum and vaccine was given to only two of these indi- viduals, and no one received proper wound treat- ment. A mildly exposed child, who received five doses of vaccine, died 176 days after being bitten. This victim could possibly have survived had a booster dose been given. Epldemiological effect of postexposure treatment with PHKC vaccine Data on human postexposure treatment and rabies deaths were obtained for Jiangxi province (Fig. 2) and also for China as a whole (Fig. 3). From October 1980 to October 1987, approx- imately 10 million persons in China received PHKC vaccine-mainly the adjuvant type-for postex- posure treatment of rabies. The large-scale use of the WHO Bulletin OMS. Vol. 68. 1990 66 64 62 o 60 E 580 r, 56 0 IL 54 Lin Fangtao Table 3: Protectivity provided by postexposure treatment with adjuvant PHKC vaccine to persons bitten by suspected rabid animals, compared with that provided by the Semple vaccine, In Jiangshu and Anhul provinces Postexposure treatment:' Control PHKC vaccine Semple vaccine No. of No. with No. of No. with No. of No. with Province Date persons rabies persons rabies persons rabies Jiangshu 1979-82 6950 9 (0.13)b 4486 18 (0.4) 808 77 (10.1) Anhui 1979-81 3138 6 (0.19) 1525 9 (0.59) 2269 112 (4.9) Total - 10 080 15 (0.15) 6011 27 (0.45) 3077 189 (6.14) ' Student's Mtest=3.6; P<0.001. b Figures in parentheses are the percentage of treatment failures. Table 4: Protectivity provided by postexposure treatment vaccine appears to have influenced the epidemiology with adjuvant PHKC vaccine to persons bitten by suspec- of the disease in Jiangxi province and, to some extent, ted rabid animals In Guanxl autonomous region and also in the entire country. Hunan province Discussion Postexposure treatment Despite the availability of several types of safe, potent No. of No. with cell-culture rabies vaccines (9-16), rabies vaccine Location Date persons rabies produced in the brain tissue of adult animals is still widely used in some developing countries. Guanxi and 1981 10000 2 (0.02)' There have been many appeals that a solution Hunan 198384 27658 11 (0.048) be sought to this problem. For example, at a WHO 1983_____84___20____658____ 11__________ Consultation in Essen, FRG, it was stated that "the Total - 37 823 21 (0.055) problem that is giving us cause for concern is how to help the developing world in the production of safer Figures in parentheses are the percentage of treatment and more potent vaccine than they are using at failures. present" (17). Subsequently, Bogel recommended Table 5: Details of the 10 deaths from rabies In Hubel province Postexposure treatment: Class of No. of days No. of days' Sex Age (years) exposure" after biting Wound Dose of vaccine Dose of serum incubation 1. M 11 11 1 Cleansed x5 NTb 176 2. M 17 III NTb NT NT NT 23 3. F 14 III 20 NT xl NT 25 4. M 9 iII 20 NT xl NT 29 5. F 16 liI 30 NT x4 NT 43 6. M 7 III 1 NT x5 NT 39 7. M 37 liI 1 NT x 155 ml 41 8. M 30 IiI NT NT NT NT 93 9. F 47 III 1 Cleansed and x5 2000 IU 30 stitched 10. F 25 III NT NT NT NT 70 See: WHO Technical Report Series No. 709, 1984 (WHO Expert Committee on Rabies- seventh report). NT = not treated. WHO Bulletin OMS. Vol. 68. 1990452 Large-scale use of PHKC rabies vaccine In China Fig. 2. Epidemiological effect of postexposure treatment with PHKC vaccine In Jlangxi province. No. of rabibs C (x 100) 10 9 8 R 7 x I 6 .2 5 > 4 3 z 1975 1976 1977 1978 1979 190 1961 1962 1963 1964 Fig. 3. Epidemiological effect of postexposure treatment with PHKC vaccine In China as a whole. 1975 1976 1977 1978 1979 1960 1981 192 193 1684 1965 that, "once costs of cell culture human vaccines have been appreciably reduced, mass pre-exposure immunization of populations at risk may be con- sidered in conjunction with other routine vaccina- tions in specific countries where rabies is highly prevalent, but not to the exclusion of emphasis on control of the disease in its reservoir host" (18). A low-cost, safe and potent vaccine for human use should evoke an early, high and persistent neutralizing antibody response. Although the adjuvant added to the vaccine can delay the response, this difficulty can be overcome by increasing the dosage on day 0 or by using high-potency adjuvant vaccine, or antiserum and vaccine in combination, for all postexposed patients, irrespective of whether they have been mildly or severely bitten. The adjuvant rabies vaccine that was licensed in China in 1980 has completely replaced the Semple vaccine; more than 50 million doses have been produced, and these have mainly been used for postexposure treatment. In China, the protective effect of the adjuvant vaccine has not only been confirmed in two incidents involving rabid wolves but also has been used for millions of postexposure treatments. The potent, stable and well-tolerated adjuvant, concentrated PHKC vaccine and FDC vaccine for alternative use were also licenced in China in 1980, and approximately 1 million doses have been produced and used for postexposure treatment. We are now planning to purify the adjuvant concentrated vaccine and the FDC vaccine. R6sum6 Effet protecteur de l'utilisatlon A grande 6chelle du vaccin antirabique PHKC (obtenu en cultures primaires de cellules r6nales de hamster) chez l'homme en Chine L'article d6crit les resultats obtenus avec divers calendriers d'administration a des volontaires de vaccin antirabique obtenu en cultures primaires de cellules renales de hamster (PHKC) soit adjuve, soit concentre et lyophilis6 (FDC). Le vaccin con- centr6 Iyophilise (activite 4,5 Ul) innocule en six doses les jours 0, 3, 7, 14, 30 et 90, et le vaccin adjuve (activite 2, 5 Ul) innocule en cinq doses les jours 0 et 7 (double dose), 14, 30 et 90, induisaient des titres d'anticorps neutralisants plus rapidement obtenus, plus eleves et plus durables que le vaccin adjuv6 innocule en cinq doses les jours 0, 3, 7, 14 et 30. La persistance des titres d'anticorps neutralisants induits par trois doses intradermiques de vaccin administrees les jours 0 (4 sites), 7 (2 sites) et 28 (un site) etait plus faible que dans le cas de six doses intramusculaires administrees les jours 0, 3, 7, 14, 30 et 90. Une immunite a mediation cellulaire (CMI) a egalement &t6 induite chez les sujets ayant requ le vaccin adjuve. L'effet protecteur de ce dernier etait meilleur que celui du vaccin Semple utilise aupar- avant et a eu un effet positif sur l'epidemiologie de la rage humaine en Chine. WHO Bulletin OMS. 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