Smallpox vaccination by intradermal jet injection*

Bull. Org. mond. Sante| 1969, 41, 771-778Bull. Wid Hith Org. Smallpox Vaccination by Intradermal Jet Injection* 3. Evaluation in a Well-vaccinated Population JOHN M. NEFF, M.D.,1 J. DONALD MILLAR, M.D.,' RONALD R. ROBERTO, M.D.3 & HERTA WULFF, Ph.D.4 Smallpox vaccinations were performed in a well-vaccinated prison population by mul- tiple-pressure technique and by intradermal jet injection using serial dilutions of vaccine. A total of 140 subjects were divided into groups, and each group was vaccinated by the multiple-pressure technique or by jet injection using I of 3 vaccine dilutions with thefol- lowing calculated titres: ID-Jet 1 = 107-° TCIDs0/ml, ID-Jet la = 106.3 TCID5o/ml, ID-Jet 2 = 106-. TCID5o/ml. Clinical observations were made at intervals during the first week after vaccination. Prevaccination and post-vaccination serum samples were obtained immediately before and 30 days after the vaccination. Results based on clinical and serolo- gical evaluations indicated that smallpox vaccination by jet injection with the ID-Jet 1 vaccine was at least as efficacious as vaccination by the standard multiple-pressure tech- nique. Data already presented (Millar et al., 1969; Roberto, Wulff & Millar, 1969) have shown that jet injection is a feasible method of performing primary vaccination and revaccination of persons with little or no immunity to vaccinia. Serially diluted vaccines administered by intradermal jet injection were as effe tive as the accepted multiple- * From the Smallpox Eradication Program, National Communicable Disease Center, Health Services and Mental Health Administration, Public Health Service, US Depart- ment of Health, Education, and Welfare, Atlanta, Ga., and Section of Virus Research, Department of Pediatrics, School of Medicine, University of Kansas, Kansas City, Kans., USA. These studies were supported in part by the US Army Research and Development Command, Office of the Surgeon General, Department of the Army. 1 Formerly Epidemic Intelligence Service Officer, National Communicable Disease Centcr, Public Health Service, US Department of Health, Education, and Welfare, Atlanta, Ga., USA. Present address: Johns Hopkins Hospital. 2 Director, Smallpox Eradication Program, and formerly Epidemic Intelligence Service Officer, National Communi- cable Disease Center, Public Health Service, US Department of Health, Education, and Welfare, Atlanta, Ga., USA. a, Formerly Chief, Smallpox Investigations Unit, Smallpox Eradication Program, National Communicable Disease Cen- ter, Public Health Service, US Department of Health, Education, and Welfare. Present address: State Department of Public Health, Berkeley, Calif., USA. 4 Formerly Research Fellow in Pediatrics, University of Kansas Medical Center, Kansas City, Kans., USA. Present address: Ecological Investigations Program, National Com- municable Disease Center, Kansas City, Kans., USA. pressure techniques. The present study was designed specifically to compare the efficacy of diluted small- pox vaccine administered by jet injection with undiluted vaccine adninistered by multiple pressure in a group of individuals with relatively high levels of residual immunity. METHODS AND MATERIALS Study population Volunteers were selected from prisoners admitted to the Evaluation and Orientation Section of the Atlanta Federal Penitentiary. Many were in process of transferring from other federal prisons; most had been admitted several times to federal prisons, and had been vaccinated on each occasion. Subjects were assigned alternately to I of 4 groups; histories of previous vaccination were obtained; evidence of primary vaccination was confirmed by inspection of primary scars and a prevaccination blood specimen was drawn. Group I was vaccinated by multiple- pressure technique using undiluted vaccine. The remaining 3 groups were vaccinated by intradermal jet injection with 0.1 ml of diluted vaccine prepara- tions. The viral concentrations used were 107 TCID50/ml for group 2, 10'3 TCID,0/ml for group 3 and 106 TCID so/ml for group 4. 2432 771 - 772 J. M. NEFF AND OTHERS TABLE I STUDY GROUP CHARACTERISTICS Group Characteristics I 2 3 4 Vaccination method and Multiple pressure I D-Jet I I D-Jet I a I D-Jet 2 vaccine dilution (undiluted) Vaccine titre a 8.5 7.0 b 6.3 6.0 Number of subjects tested 37 35 33 35 Age of subjects: Mean 38 38 36 39 Range 26-52 24-51 24-58 25-62 Mean No. of years since last vaccination 7 9 9 11 Mean No. of previous vaccinations 6 4 4 4 No. of subjects with 3 or more previous vaccinations 24 16 20 17 Pre-vaccination neutralizing- antibody titre <41 10 7 7 5 41-160 3 11 6 11 161-320 11 9 11 12 321-640 7 6 7 6 >640 6 2 2 1 Geometric mean titre 142 132 139 140 a Expressed as log TCID; /ml. b The titre of 7.0 is actually for a 1 : 33 volumetric dilution, arbitrarily designated "ID-Jet I"(expressing dose relationship) thereby accounting for the apparent 0.5 logo discrepancy. Vaccine Lyophilized calf lymph smallpox vaccine from a single commercial production lot' was used for all vaccinations. This vaccine was found to have a titre of 108.5 TCID50/ml, when titrated in primary rhesus monkey kidney cell culture using 1/2 log dilution steps (Millar et al., 1969; Roberto, Wulff & Millar, 1969). For multiple-pressure use, the vac- cine was reconstituted with the standard commercial diluent containing 50% of glycerol (USP) and 0.25% of phenol (USP) in sterile distilled water. Vaccine for jet injection was prepared as follows: Vaccine from a standard 10-dose vial (multiple- pressure use) was reconstituted with 10 ml of phy- siological saline (0.85% sodium chloride). The preparation was termed " ID-Jet 1 vaccine". A I Kindly provided as Dryvax, Lot 177101, by Wyeth Laboratories, Inc., Marietta, Pa., USA. sequential 5-fold dilution in physiological saline yielded vaccine designated as " ID-Jet la" and a 10-fold dilution " ID-Jet 2 " (Table 1). Calculated titres of these diluted vaccines were: ID-Jet 1 = 107-0 TCID50/ml, ID-Jet la = 106-3 TCID50/ml, ID-Jet 2 = 1060- TCID50/ml. Vaccination techniques Each subject was inoculated on the left deltoid area either by the multiple-pressure method or by intradermal jet injection. Multiple-pressure vaccina- tions were performed by 1 vaccinator with a single pointed needle making 30 tangential pressures through a drop of vaccine. Intradermal jet injection vaccinations were per- formed with the automatic hypodermic jet-injection apparatus2 equipped with the intradermal nozzle 2 Manufactured by the Scientific Equipment Manufactur- ing Corporation, Lodi, N.Y., USA. SMALLPOX VACCINATION BY INTRADERMAL JET INJECTION. 3 (Millar et al., 1969). Jet-injection inoculations were performed with the control set to deliver 0.1 ml. Clinical and serological evaluations The inoculation site was examined immediately after vaccination and then on days 2, 4 and 7. (The day of vaccination was designated " day 0 ".) Maximal vertical and horizontal diameters of erythema or of induration or both were measured and evidence of vesiculation was noted and recorded at each reading. A successful revaccination was defined as a " major reaction " according to the criteria of the WHO Expert Committee on Smallpox (1964), i.e., "... one which, on examination one week (six to eight days) later, shows a vesicular or pustular lesion or an area of definite palpable induration or congestion surrounding a central lesion which may be a scab or ulcer ". All other reactions were termed " equivocal ". Samples of blood (10 ml) were drawn just prior to revaccina- tion and again 30 days after vaccination. The sera were separated and frozen at -20°C within 6 hours of collection and remained in this state until sero- logical studies were conducted. Serum-neutralizing antibodies were determined by techniques already described (Millar et al., 1969). A 4-fold rise in titre was considered to be a significant serological response. RESULTS Characteristics of the study group Various characteristics of the study group are summarized in Table l. All the subjects had been vaccinated several times. At least half of each group reported vaccination within the previous 5 years and had prevaccination neutralizing-antibody titres greater than 160. By chance, the multiple- pressure group was composed of subjects who, according to the background data obtained, had been vaccinated rather more frequently than those in the other groups. Clinical results The cutaneous reactions to vaccination were sharply accelerated as expected in a group with significant residual immunity. The proportion of each group (1-4) demonstrating lesions with an area of erythema of at least 1 cm2 reached a maximum (92%, 86%, 88%, 69%, respectively) on the fourth day after vaccination and declined thereafter; the mean area of erythema in all groups (1-4) also was greatest during the first 4 days. The proportion of subjects demonstrating major reactions and equivocal reactions is shown in Table 2. The responses of the first 2 groups (reci- pients of multiple-pressure (undiluted) and ID-Jet 1 vaccines) were similar. Major reactions were demonstrated in about three-fourths of the subjects in both groups. The proportlon of major reactions declined in recipients of ID-Jet la and ID-Jet 2 vaccines. Only 2 subjects, 1 vaccinated by multiple pressure and 1 with the ID-Jet 2 vaccine, demon- strated no cutaneous response to vaccination. Although an occasional subject demonstrated a minimal degree of regional adenopathy, no person had any significant systemic reaction following vaccination. TABLE 2 CUTANEOUS REACTIONS a Group Vaccination method Vaccine Total No. Major reaction Equivocal reactionro and vaccine dilution titre b of reactions No. % No.c % 1 Multiple 8.5 37 28 76 9 (1) 24 pressure (un- diluted) 2 ID-Jet 1 7.0 35 25 71 10 29 3 ID-Jet la 6.3 33 18 54 15 46 4 I D-Jet 2 6.0 35 15 43 20 (1) 57 a Criteria of the WHO Expert Committee on Smallpox (1964). b Expressed as log TCIDso/ml. c Values in parentheses indicate number of subjects with no dermal response. 773 J. M. NEFF AND OTHERS TABLE 3 NEUTRALIZING-ANTIBODY RESPONSE BY PREVACCINATION TITRE Serological results Neutralizing-antibody responses are presented by group and prevaccination titre in Table 3 and Fig. 1-4. Those subjects with prevaccination titres of less than 40 demonstrated a uniform response to vaccination irrespective of the vaccination method or the dilution of vaccine. Of the 29 subjects with prevaccination titres of less than 40, only 4 (1 in each study group) failed to develop a 4-fold rise in neutralizing-antibody titre. Among those with prevacciination titres of 160 or above, however, the influence of the various initial viral doses can be seen. Of 17 such subjects receiving ID-Jet 1 vaccine, 6 (35 %) developed a 4-fold antibody rise. Of the remaining 63 subjects with prevac- cination titres of 160 or above, only 6 responded with an antibody rise, 3 after multiple-pressure vaccination and 3 after ID-Jet 2 vaccination. Of the methods used, intradermal jet injection of the vaccine containing 107 TCID50/ml seems to be the most vigorous immunological stimulus in this, presumably, highly immune population. Among the remaining 3 groups, differences in serological responses were insignificant. Correlation ofdermal reaction with antibody response Only a gross correlation was observed between the dermal reaction and antibody response (Table 4). TABLE 4 NEUTRALIZING-ANTIBODY RESPONSE BY CUTANEOUS REACTION AND PREVACCINATION NEUTRALIZING-ANTIBODY TITRE Vaccination Gopmethod and Group vaccine dilution 1 Multiple pressure (undiluted) 2 3 4 Total ID-Jet 1 ID-Jet la ID-Jet 2 Fraction showi Number Vaccine of Major reaction titre b subjects ivac- Prevaccina- Prevaccina- cinated tion tion titre <160 c titre >160 c 8.5 7.0 6.3 6.0 37 35 33 35 8/9 (89) 10/13 (77) 5/6 (83) 3/9 (33) 3/19 (16) 4/12 (33) 0/12 (0) 2/6 (33) ng 4-fold or greater rise in antibody titre a Equivocal reaction Total c 11/28 (39) 14/25 (56) 5/18 (28) 5/15 (33) 26/37 (70) | 9/49 (18) 35/86 (41) Prevaccina- Prevaccina- tion tion titre <160 c titr6e >160 c 1/4 3/5 4/7 3/7 (25) (60) (57) (43) 11/23 (48) 0/5 (0) 2/5 (40) 0/8 (0) 1/13 (8) 3/31 (10) Total c 1/9 (11) 5/10 (50) 4/15 (27) 4/20 (20) 14/54 (26) a i.e., number with 4-fold antibody rise/number with dermal reaction. b Expressed as log TCIDs0/mI. c Percentages in parentheses. 774 SMALLPOX VACCINATION BY INTRADERMAL JET INJECTION. 3 E E I. E 0 0 11 o ._ \ - I * * -\1 ) * o\ 0~\ *\Q\ ' a! uoioD1 ,DAsod -o 6o1 |414L O!4DU!)3DA-4SOd C) C 0 _ 0 0C) 0)C4 II (E) 0 \0 * 0 \ \.\\. .\ 0 \ . - 0 0.* . .\ 0\ ' \\ co (fl 0100 o a- -a E 00. CO 0 o o lm O oE 00E 0 a co - o 6 oHo ° a) ._ C C) 0 t *i > tl 775 w z a u H zw0 7 C) O 0 0 LL < 0 > w 0: u) a.O 2 oa IL, Z t < U) Zz w zFF- > Z >z a- z 00 z z 2 z (D O> ZL _ <-_ H ZLL z 0< - a. - O) D 0 Z. W O 0 z LL - a) 2z C< Z 01! U01)4DUlD3DA-4Sod jo Bo- o 0 o°° XDA4S_ fl4! U0)4OU!)DO^-4S°d . 0 . * J. M. NEFF AND OTHERS (4) C C o 00 U E >LI **\ * 0 a ZL IGo| I I'o J. * .'-' ' *'*0 S.. 0~ ~ ~ ~~~'',C- (0~ < @j!4 uo!4Du !zoD^~~~~~~~~~~~~~~~~~~~~~~~C -4s ioD > _ *0\ 0 2 (00 a. t~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 00 Z -o \ E O F r ' \ \ E k~~~~~~~~~~~~~M ( 0o I \ -J a 0.4! \O tD! oDA4Sci zM 0~~~~~~~~~~~~~~~~~~ N N q _a V} ss b t0 n O oZD~~~0 z cl 4)! o$uzo.4o oDn.v 0~~~~~~~~~~~~~~~~~ oo > s s < 0 w > o X w ^ q J > 0~~~~~~~~~~~~~~~~~~~~ -J - oF -}A _ - Z ~~~~~~~~~J4!tU014DUI33DA-4SOd oB- 0.0 10 (0 N - , -40 C( 0 a 0 U. z 0.44)4 UOI4DUi ~~~~~~~~~~~~~~~~DA.4S0 ~~~ 776 SMALLPOX VACCINATION BY INTRADERMAL JET INJECTION. 3 The presence of vesiculation, the area involved and the time of development of the vesicle, the extent of erythema and induration, and combinations of these measurements did not show close correlation with the neutralizing-antibody response. In general, however, there was a greater proportion (41 %) of 4-fold responses among those with major reactions than that observed (26%) among those who had equivocal reactions. This correlation was no more specific for those with prevaccination titres less than 160 than for those with prevaccination titres greater than 160. In the ID-Jet 1 group alone, there was no correlation between dermal response and antibody rise. In this group, approximately half of the sub- jects showing either a major reaction or an equivocal reaction demonstrated 4-fold antibody responses. DISCUSSION In the present study, it was found that successful smallpox revaccination could be accomplished by jet injection in well-vaccinated subjects. It is appa- rent that jet injection using a smallpox vaccine with a titre of 107-0 TCID50/ml is at least as reliable in inducing cutaneous and antibody responses as the multiple-pressure method using undiluted vaccine. The serological response in subjects with high pre- vaccination neutralizing-antibody titres was better following the jet injection of ID-Jet 1 vaccine than by any other method. This suggests that the amount of vaccinia virus delivered to target cells by this method was greater than by either multiple-pressure vaccination with undiluted vaccine or jet injection of the more dilute vaccines. Smallpox vaccination with both ID-Jet la and ID-Jet 2 vaccines did not produce cutaneous results comparable to vaccination by the multiple-pressure method or the ID-Jet 1 vac- cine. The over-all serological neutralizing-antibody responses, however, were similar with these diluted vaccines to those induced by the multiple-pressure method. The analysis of these data permits delineation of a jet-injection vaccination dose-response relationship for groups with varying immunity to vaccinia virus. In a previous article, Millar et al. (1969) defined this response for a group of remote revaccinees with limited residual immunity; Roberto et al. (1969) defined this relationship for primary vaccinees and in the present study it was determined for well- vaccinated subjects. This composite analysis is presented in Fig. 5. As might be expected, the infecting dose by jet injection necessary to produce FIG. 5 JET INJECTION VACCINATION RELATIONSHIP BETWEEN CONCENTRATION OF VACCINE AND PROPORTION OF MAJOR REACTIONS INDUCEDa 0 tz 60 0 ,, 50. o8 ° 40 ID 30 / / YR-0.68 +0.26 X / N /N/." / /O0 YN =1.2S+0.28X 4 5 6 Vaccine dose expressed os log TCID50 ml(0.1 ml innoculum) a Data of Roberto, Wulff & Millar (1969) (YR) O Data of Millar et al. (1969) (YM) * Data from this paper (YN) a In groups with differing immunities. a major reaction in 50% of a group of human volunteers is directly proportional to the immune status of the population studied. For primary vac- cinees, this theoretical vaccine dose expressed as log TCID50 is approximately 4.5; for remote revac- cinees, 5.5; and for well-vaccinated subjects, ap- proximately 6.2. Espmark (1965) has performed a similar theore- tical analysis for vaccination with the multiple- pressure technique. In his study, the theoretical vaccine dose expressed as log TCID50 necessary to produce a cutaneous reaction in 50% of individuals tested was approximately 5.6 for primary vaccinees (by extrapolation), 6.1 for remote revaccinees, and between 6.6 and 7.1 for well-vaccinated subjects. The consistency of the dose-response relationship among immunity groups, as seen in these studies and in the work of Espmark, supports the comparability of 3 777 who 91089 778 J. M. NEFF AND OTHERS smallpox vaccination by jet injection with the tradi- tional multiple-pressure method. It suggests also that the jet-injection method is considerably more efficient in delivering vaccinia virus to target cells than is the multiple-pressure method. Comparing Espmark's data, as characteristic of typical multiple- pressure vaccination, with those presented in this paper, as characteristic of typical intradermal jet injection vaccination, this difference in efficiency may be estimated. It appears that intradermal jet injection vaccination requires only a vaccine with a concentration of about one-tenth that required for effective multiple-pressure use. With some con- sistency, this appears to apply generally to primary vaccination and to revaccination, both early and late. In conclusion, smallpox vaccination by intra- dermal jet injection using vaccine with a titre of 107 TCID50/ml is as effective a means of immuniza- tion as smallpox vaccination by the presently accepted multiple-pressure technique using undi- luted vaccine. The first two studies in this series demonstrated the efficacy of intradermal jet injec- tion in primary vaccinees and remote revaccinees. This paper shows that it is effective also in popula- tions of well-vaccinated individuals. RESUME LA VACCINATION ANTIVARIOLIQUE PAR INJECTION INTRADERMIQUE SOUS PRESSION: 3. EVALUATION DE LA METHODE DANS UNE COLLECTIVITE PRESENTANT UN NIVEAU D'IMMUNITE RELATIVEMENT ELEVE On a montre precedemment l'interet que presente la methode de l'injection sous pression pour la primo- vaccination antivariolique et pour la revaccination de sujets chez lesquels I'immunite residuelle est nulle ou faible. Dans ce troisieme et demier article, la mdthode est evalu&e sous l'angle de son efficacite lorsqu'il s'agit de vacciner des sujets b6n6ficiant d'une protection relative. Cent quarante volontaires dejat vaccines a une ou plusieurs iepi ises ont ete revaccines soit par pressions multiples a l'aide d'un vaccin non dilue contenant 108,5 doses infectantes de culture de tissu (DICT50) par milli- litre, soit par injection sous pression de vaccins dilues titrant 107, 10683 ou 106 DICT50/ml. Les reactions cutanees ont et examinees et mesurees les 2e, 4e et 7e jours suivant la vaccination, leur interpretation etant basee sur les criteres recommandes par le Comite OMS d'experts de la Variole (1964). Les reponses serologiques ont ete apprdci6es par titrage des anticorps neutralisants dans les serums preleves avant et 30 jours apres la revaccina- tion. Le taux d'apparition de reactions majeures a ete de 76% chez les sujets vaccines par pressions multiples 'a l'aide de vaccin non dilue; chez les sujets vaccines par l'injecteur sans aiguille, les taux ont ete de 71 % (vaccin titrant 107 DICT50/ml), de 54% (vaccin titrant 106 3 DICT50/ml) et de 43% (vaccin titrant 106 DICT50/ml). Apres injection sous pression de vaccin titrant 107 DICT50/ml, les titres d'anticorps seriques se sont accrus dans la proportion de 4 fois ou plus chez 54% des sujets. Chez les sujets vaccines par les autres methodes, une elevation correspondante des titres n'a ete relevee que dans 26 a 32% des cas. La corrdlation entre l'intensite des reactions cutanees et l'amplitude des reponses sero- logiques a ete tres approximative. Ces resultats, ainsi que ceux des deux etudes prdc6- dentes, montrent que l'efficacite de la vaccination par injection sous pression d'un vaccin titrant 107 DICT50/ml n'est en rien inferieure a celle de l'inoculation d'un vaccin non dilue par pressions multiples, la dose optimale pour les vaccinations de masse etant de 0,1 ml. REFERENCES Espmark, J. A. (1965) Acta path. microbiol. scand., 63, 116-126 Millar, J. D., Roberto, R. R., Wulff, H., Wenner, H. A. & Henderson, D. A. (1969) Bull. Wld Hlth Org., 41, 749-760 Roberto, R. R., Wulff, H. & Millar, J. D. (1969) Bull. Wid Hlth Org., 41, 761-769 WHO Expert Committee on Smallpox (1964) Wld Hlth Org. techn. Rep. Ser., 2.83, 20