Jpn. J. Infect. Dig., 53, 47‑55, 2000

ReviewDevelopment of a Live Varicella Vaccine‑Past and FutureMichiaki Takahashi *The ReseallCh Foundation for Micy10bial Diseases at Osaka UniversiO!,
Yamadaoka 3‑1, Suita, Osaka, Japan(Received March 1 5, 2000. Accepted March 30, 2000)
SUMMARY: Background of the development of a live varicella vaccine, including studies on the attenuation ofmeasles and polioviruses, and transformation experiments of cultured hamster and human cells with conditional

lethal mutants of adenovirus and herpes simplex virus w.ere described･ Varicella‑zoster virus (Oka strain) was
pFssaged in guinea pig cells, and the resulting virus (vacclne Virus) was found to have a higher afrlnityto guinea
plg Cells･ It was recently proved that variationヲofbase sequence occ†rred exclusively in gene 62 (immediate‑
early gene) in comparisop of vaccine Oka vlruS and parent Oka vlruS･ This variation is prヲSumed to haveoccurred during passage ln guinea pig cells･ Live.varicella vaccine (Oka strain) has increas)ngly been usedthroughout仇e world. It was also fわund in a prelimlnary Shdy that glVlng the vaccine to the elderly enhanced

humoral and cell‑mediated immunity, leading to a prevention of post herpetic neuralgia. A large field trial is now
golng On in the United States to immunize the elderly for the purpose of prevention of herpes zoster, particularly
post herpetic neuralgia.

Table I. Passage ofpolioviruS (Type 3, Saukett strain) in developing chick

Backgroundembryo andaltemate passages in monkey kidney cell and chick embryo
cell cultures

1. Attenuation of measlesvirus, rubella virus, andChick embryo

poLioviruses
In 1959‑ 1 962, I worked on the development of attenuated

PaSSage

5｢live measles vaccines in the laboratory of Professor Yoshiomi
Okuno, Osaka. This virus was attenuated by passage in theamniotic cavityand chorioallantoic membrane of developing
chick embryos (I ,2)･ Besides my work with measles virTs, I
was also asked to do a study on the adaptation ofpoliovlruStypes 1 and 3 to chick embryo cells･Asis wellknown, polio‑
virus type 2 grew wellindeveloping chick embryo cells, but
types 1 and 3 did not. I attempted to adapt these viruses ‑particularly type3 ‑ to chick embryo cells by altemate passage
in chick embryo cells and monkey kidney cells (3,4) (Table

I ). nLe attempt finally failed: no continuous growth ofpolio‑
viruStype 3 took place in chick embryo cells. However, after

M.K. cell

Chick cell

culturecultureseveral alternate passages the virus was found to be

thermosensitive (i.e., thetiter of the passaged virus was lower
at 34oC thanat 390C whereas titers of the onglnal strain werecomparable at these two temperatures) (Table 2) and to ber(9 ‑‑二二二;ナ㊥

less neurovirulent when inoculated into the thalamus ofmonkeys (Table 3).

From these studies, I leaned that passageinforeign‑Species
cells is a convenient and effective means by which to attenuate;,=J･‑‑‑‑.‑‑‑‑ t‑viruses for use in live virus vaccines.

2. Malignant transformation of cultured cellswith

plaque purification (MC strain)human adenovirus and herpes simplex virus(&om ref. 3)

I had long been interested in the possible causative rela‑tionship between human viruses and human cancer. In 1962,

tumor formation by adenovirus type 12 was reported in new‑was classified as a nontumorigenic virus, caused lytic infec‑

bom hamsters (5). Stimulated by that finding, I started in vltrOtion in hamster embryo cells. Both viruses are lytic to humantransformation experiments with adenovirus type I 2; no viralembryo cells.

growth or lyticviral infection was detectable in inoculated

Thus we tried to obtain conditional lethal mutants or

hamster embryo cells. In contrast, adenovirus type5, which

adenoviruStype 5and to ascertainwhether such mutants could ‑*Corresponding author: Tel:+8 1 ‑6‑6877‑4804, Fax:+8 1 ‑6‑6876‑

cells. We obtained both temperature‑sensitive mutants, whichlike adenovirus type 12 ‑ cause the transformation of hamster

1 984, E‑mail: michiaki@biken.osaka‑u.ac.jp

did not grow at 38.5oC, and host‑dependent mutants, which

47

Table 2. Comparison of infectivity of origlnalSaukett andaltemately chick embryoce11‑monkey kidney cell passaged viruses incubated at 37oC and 40oC

Vims 蒜儲7F友W"

eR

ﾓ

37oC

認貿fW&V鼎

0riginalSaukettstrain
CE5MKlb繧b繧

CE5MK3cc2b纈

CE5MK̲5cc4r

CE5MK7cc6

V也F友W&

B

襪C

106,5

2

105.3

ｳb

104.0

CE5MK7cc6 +lplaquing(MCstrain)

6

2

106.8

104ー7

r

3v

2

"
8

b纈

ｳ

<101 薙

R纈

(&om ref. 4)

Table 3. Comparison of neurovirulence of original and passaged polioviruS (Type 3, Saukett strain)
in monkey by intracerebralinoculation

Vims 微&没匁

ﾂ6VｶWGG7G&

問･CE,MK3cc22)

Ⅵraldose(PFU/ml)I)r

Paralysis"

STﾔｲﾆ63c2

10T6

1/3

CE5MK7cc6 +lplaqulmg
r

107.3

B

0/3

1)0.5 ml intrathalamic itlOCulation

2)saukett strain. 5 chick embryo passage and 2 altemate in MK cell and chick cell and 1 MK cell passaged3)saukett strain. 5 chick embryo passageand 6altemate passage in MK cell and chick cell and I MK cellpassaged(&omref.3)

caused lytic infection in human but not hamster embryo cells

family had severe chickenpox in 1964, with high fever and(6). Usinganestablished hamster embryo cell line (Nil cells)

widespread rashes lastlng for 3 days, I began to consider

that, unlike primary Cultured cells, was readily transformed,

how this disease might be prevented by vaccination. Since I

we observed malignant transformation with both mutants

knew that live vaccines induced solid immunlty against(7,8). However, We detected no transformation of humanembryo cells with these mutants. This finding was consistentbegirmmg of the study was to develop a live attenuated varicellawith the lack of evidence of a causative relationship between

VaCClne.

diseases such as measles and polio, my thought from theTwo major Problems had to be considered. The first washuman adenoviruses and human cancer.

In 1971, Duff and Rapp reported that hamster embryo
fibrob)asts were transformed withultraviolet‑irradiated herpes

the possible oncogenicity of varicella‑zoster virus (VZV),

simplex virus type 2 (HSV‑2) (9). We found their work

experiences described above, I had become convinced thatinteresting and attempted to transformhamster cells withtemperature‑sensitive mutants at a nonpermissive temperature.
Approximately 2,700 clones of HSV‑2 Were isolated from

HSV is either minimally or totally unrelated to malignancy

which is a member of the herpesvirus group. Through thenonpermissive at 38.50C were examined for the ability toin human cells. Although it was difficult torule out VZV as acause of malignancies, VZV had never been linked to any
formofcancer. After my studies, Gelb et al. (I I) reported
that their fresh VZV isolates transformed hamster embryotransform hamster and human embryo cells at 38.5oC.

cells morphologically, but they later reported ( 12) that thisHamster embryo cells were transformed by three mutants ( 1 0).

observation was not reproducible. Thus, even in vitro, it

Transient transformation of human embryo fibroblast wasseemed unlikely that VZV could induce malignant change.

mutagcnized stock virus at 32oC, and 42 clones found to be

documented with one mutant, but resulted in the failure of

The second problem was the possibilitythat live varicellaserial passage of the cells so that the finding was not repro‑

vaccine virus would become latent, perhaps resulting in the

ducible. Later on, We attempted repeatedly to transformlater development of zoster. I presumed that attenuated virus

human embryo fibroblasts with ultraviolet‑ irradiated humanwould have less c叩aCity也an wild‑type vims to replicate in

HSV‑2, but were unsuccessful.

humans and thus to become latent. In addition, I expected

TTLrOughthese experiments, I became convinced dlat humanadenovirus and HSV, althoughknown to induce a malignantthat symptoms of zoster caused by attenuated virus might betransformation of hamster and rat embryo fibroblasts (i.C.,

Thus I thought thatthese two issues were not obstacles to theforeig.n‑species cells)I are little related ‑ if at all ‑ to onc0‑

development of a live varicella vaccine.

less severe than those of disease caused by wild‑type viruses.

genesIS in human cells (i.e., indigenous cells).

DifrICulties in preparlng "cell‑free''VZVMotiyations fわr and problems im tlle deyelopment

Since the earliest studies on in vitro propagation ofVZV,

of a live variceua yaccine

it has been recognized that virus produced in cell cultures

Chickenpox is usually a mild illness but occasionally mani‑

remains strongly cell associated; the inabilityto obtain cell‑

fests as a severe disease in children. After a member of myfree infectiousvirus has hampered biological and immuno‑

48

logical studies of this virus. Caunt (13) and Caunt and Taylor‑

Rationale for and design of a live varicella vaccine

Robinson (14) showed that infectious VZV could be isolated
in a cell‑free state followlng an ultrasonic disruption of

VZV spreads from cell to cell, formlng distinct foci that

infected prlmary human thyroid cells. Shortly thereafter,are visible by microscopy even in unstained cell cultures andBrunell (1 5) reported the isolation of cell‑free virus fromare clearly seen after methylene blue or nuorescent antibody

infected human embryo lung fibroblasts. Refeming to thosestaining･ Cell‑mediated immunityse?ms essential l 0r at least
as important as humoral immunity‑ ln Preventing the spreadofVZV invivo. Since inactivated or subunit viral antigens

papers, We undertook studies to identify a suitable method
for the isolation of cell‑free virus from infected cultures andthe composition of a suspending medium that would keep

are usually weak inducers of cell‑mediated immunlty, We

the infectivityofthe virus as stable as possible. We reasoned

reasoned that a live vaccinemight be the most useful for thethat the followlng Procedures would be likely to yield high‑prevention of varicella.

titered cell‑free virus from infected cells: 1 ) use of cultured

It had been very difrlCult to demonstrate the pathogenicity

cells in the grow血phase fb∫ inoculation of the vlmS; 2) high‑of VZV in experimental animals. Therefore, we anticipatediヮput multiplicity,with infected cells (rather than cell‑freethat the attenuation ofVZV would be proven only by extensive

vlruS) being used for inoculation because of the difficultyof

clinical trials, and that testing or only a limited number ofobtaining a sufficient dose of cell‑free vlruS; and 3) harvest‑
ing of the infected cell monolayer (by treatment with EDTA)

method of attenuation, as described previously, was used. Of

before the appearance of advanced cytopathic changes withthe various kinds of nonprlmate Cultured cells tested forcandidate strains would be feasible. The classical (empirical)

susceptibilityto infection with the Oka strain ofVZV, only

subsequent preparation of the infected cell suspension.

Because VZV is highly heat‑labile, particular caution was

guinea pig embryo fibroblasts (GPEF) were found to berequired in the selection of a suspending medium that would

susceptible.

preserve its infectivity. AAer a comparison of various media,

VZV (Oka strain) was passaged ll times in HEL cells at
34oCand 12times in GPEF cells at 37oC,andthen propagatedsimple phosphate‑buffered saline (Ca, Mg free) was selected
as the most suitable with sucrose (final concentration, 5%),
sodium glutamate (0. 1%), and fetal calf serum (10%, or 2.5%

in human diploid cells (W1‑38). The virus thus obtained
exhibited an enhanced capacity for growth in GPEF than theoriginal or other wild‑strains. The biologicaland biophysicalgelatin hydrolysate in case of vaccine preparation)( 1 6). With
this medium, the decrease in infectivityduring storage atproperties of this vaccine virus were described in detail in‑700C was minimal; in fact, no decrease was detectable after

later.reports (I 8‑20) (Table 4･5)A The results suggest that thevacclne Virus is a variant with host‑dependency.

storage for 1 year.

Recently, variations betwecnthe vaccine viruSandthe parent
Oka strain have been identified in nucleotides of viral genePrimary isolation of vaccine virus

62 (immediate‑early gene) (2 1 )･ It is speculated that chang?s

Fluid was taken &om the vesicles ofa 3‑year‑old boy whoin gene 62, which seem to have occurred during passage ln

had typical chickenpox but was otherwise healthy. The fluid

gulnea‑PIS embryo cells, may be responsible for the attenua‑

was stored at ‑700C until it was inoculated onto prlmarytion of the parent Oka strain.

cultures of human embryo lung (HEL) cells. At a temperatureof34oC, characteristic foci appeared a触r 7‑ 10 days. TYLe Virus

Early clirLicaltrials: vaccination of healthy andwas designated as the Oka strain since this was the sumame

hospitalized childrenof the boy from whose the vescular nuid it was derived (17).

With the informed consent of the parents, healthy children

Table 4. Infectivity of vaccine (Oka) and wild‑type stmins ofVZV in GPEFand HuEF
Ⅵral 一iter in indicatedstmin Sou,ce No･ of passages cells (PFU/0.2 ml)
in HEL cells

GPEF

Infectivity ratio

HuEF(GPEF/HuEF)*

Oka
一t o5768924457

Vacc ine

7.Ox103'

8.5X1032.8xl026.8xl03

Tsuchiyama Varicella5.2xl01

1.5xl03

Inoue Varicella

6.6×102

1.3×104

Watanabe Varicel la

5.8×101

1.6×103

Paren tal

Varicell a

Wada Varicella

3.8X1026.2xl03

Terada Varicella2.2×102

1.7×104

Morita Zoster

1.2XIO2

6.5X103

Kato

3.8×101

1.2×103

ZosterTakenaka Zoster

1.5XIO2

7.OX103

Yamashi ta Zoster

5.8×101

1.3×103

Yamaguchi Zoster

I.2xl02

1.9xlO3

E I len Varicel la

8.0×101

2.1 ×103

0000000000000

82糾.03 5036.0t.0t.032Mo6.0‑5‑上U‑30 2‑5tJ8

GPEF; Guinea Pig Embryo Fibroblast, HuEF; HumanEmbJyO Fibroblast'The mean ratio (± SD) except for vaccine virus was 0.038±0.015(Bom ref. 20)

49

Table 5. AdsorptlOn Ofvarious strains ofVZV to GPEL, GPES, and GPEK cells assessedby the infectious center assay
Input virus No. (PFU) of infectious centers (%) with
dose

Oka

(PFU)

GPEL

GPES

2.6xlO2(36.5)

GPEK

7.0× 1023.7xlO2(52.8)8

l.3X101(I.8)

4.8×103

1.9× 102(4.0)

2.4× 102(5.1)

9.6× 100(0.2)

1.1XIO3

8.7XIOI(7.9)

1.3xl02(12.2)

5.5X100(0.5)

2.1xl03

1.1×102(5.1)

8.8×101(4.2)

2.1 ×100(0.1)(vaccine)

Oka(HEL, 5th passage)
Kawaguchi(HEL, 1 0也passage)
Inoue(HEL, 5也passage)

GPEL; Guinea Pig Embryo Lung cells, GPES; Guinea Pig Embryo Skin cells

GPEK; Guinea Pig Embryo Kidney cells

a Number of infectious center at 4 h postinfection (PFU)
× 100%

Input virus (PFU)

GPEL, GPES,and GPEK in 60‑mm plastic plates were inoculated with the above dose ofcell‑&ee viruses. At 4 h a洗er inoculation, cells were trypsimized,andaninfectious center assay was

performed on HuEF cells.
(斤om 一et 19)

children)from 21 families were vaccinated, mostly within 3days after exposure to theindex cases. None of the vaccinated

who were living at home and had no history of varicellareceived various doses ofOka vaccine virus. A dose of 500
PFU ehcited seroconversion in 19 of20 children. Even at achildren developed symptoms of varicella. In contrast, all I 9

dose of200 PFU, an antibody response was detected in 1 I of

unv.accinated contacts (from 1 5 families), exhibited typical

1 2 children. No symptoms due to vaccination were detectedin these children.

varlCella symptoms 10‑20 days after the onset oftheindex
cases. Inthree families, one sibling contact receivedthe vaccine

The flrSt Clinical trial of the vaccineinhospitalized children
was undertaken in an effort to terminate the spread of vari‑

oped symptoms, whereas all unvaccinated controls exhibitedcella among children with no history of the disease (17). In

typical symptoms. In general, theantibody titers alter clinicaland the other did not; none of the vaccinated children devel‑

the hospital where the trial was conducted, chickenpox had

varicella were 8‑ 1 0 times higher than those after immuniza‑

frequently spread in the children's ward with severe cases ontion. This study clearly demonstrated that vaccination soon

some occasions. In this protocol, children with no history ofafter exposure was protective against clinical varicella.

variceIla were vaccinated immediately after the occurrence

ln another clinical study (25), immunized children on aof a case of varicella. These children suffered舟om conditions

hospital ward were protected desplte Subsequent exposures

including nephrotic syndrome, nephritis, purulent menlngitis,

to natural varicella and herpes zoster during the 9 months

and hepatitis. Twelve children had been recelVlng COrtico‑aRer vaccination. A鮎r 2 years of follow‑up of 1 79 vaccinatedsteroid therapy. Anantibody response was documented in all

children, including 54 children who had been receivlngof the vaccinated children;within 10‑14 days after vaccina‑

steroidtherapy, 50 (980/.) remained seropositiveinthe neutral‑tion, six children developed a mild fever, and two of the six

ization test, and only one of 13 household contacts of cases

developed a mild rash. It was uncertain whether these reac‑manifested mild varicella (10 vesicles but no fever) (26).

tions Were due to vaccination or to naturally acquiredinfection
modified by vaccination. No other climical reactions or

vaccination had a similar protective effect (27). Varicellaabnormalities of the blood or the urine were detected. Thus,

developed in an l1‑month‑old infant on a ward for 86

On this ward, the spread of varicella infection was prevented

children. A total of33 children over 1 1 months of age were

exceptinone case: a child who was not vaccinated because

vaccinated; 43 children less than I 1 months of age were not

his mother mistakenly believed that he already had varicellavaccinated, partly becausethey were expected to still possess

became severely ill. This study offered the first proof that thevaccine, Oka strain was well tolerated by patients recelVlng

platemal antibody･ A small viral dose (80 PFU) was used for
Immunization. Of the vaccinated group, eight developed aimmunosuppressive therapy and sti汀ed hopes that thismild rash and one of these eight had a mild fever (less thanln an institution for children less than 2 years old, prompt

38oC) in 2‑4 weeks after vaccination. In contrast, typicalvaccine would prove practical for the prevention of varicella.

varicella developed in all 43 unvaccinated children during

the 10 weeks after onset of the index case. Symptoms weresevere in 16 cases, with con fluent vesicles and high fever;Clinical trialswith yaccines prepared in human
diploid cells

a洗er recovery, scars remained in 13 of these 16 cases. These

When a shortage in the supply of WI‑38 cells became aconcem (22), MRCl5 cclls (23) were assessed. A master seed
lot was prepared at the second passage level in MRC‑5 cells
after three passages in WI‑38 cells, and vaccines were subse‑
quently produced exclusively in MRC‑5 cells.

results suggested that vaccination with as little as 80 PFU
frequently stopped the spread of varicella among children inclose contact with one another.

Vaccination of childrenwith malignant diseases

In an examination of its protective e爪cacy, the resulting

vaccine was glVen tO Susceptible household contacts immedi‑

In the first vaccination trials in children with malignant

ately aRer exposure to varicella (24). Twenty‑six contacts (alldiseases wi仇vims doses of200, 500, or 1500 PFU, chemo‑

50therapy was suspended for 1 week before and I week after

latter, and only long‑term studies of vaccinees would provide

vaccination ( 1 8,28,29). Of 1 2 immunized children with acutean answer. They reminded readers that in any experimental

lymphocytic leukemia (ALL), 1 0 had been in remission for
6 months or less, 1 for 9 months, and 1 for 48 months. Of
these children, four had fewer than 3000 white blood cells/

endeavor involving human beings, therisM)enefit ratio is of

mm3, but most had positive skin‑test reactions withwell outweigh the potential dangers, particularly in high‑risk

dinitrochlorobenzene, purified protein derivative, or phyto‑

persons ･

immense importance. On the basis of the available data, they

concludedthat the potential benefits of varicella vaccine might

Thus in 1977 Conmicting oplnlOnS Were exchanged among

hemagg lutin in.

Three of 12 children developed amiId rash; 13 (with 1500

several distinguished scientists interested in viral vaccines.

PFU), 30 and 25 (with 200 PFU) papulae or incomplete

Most of them favored continued work on a live varicellavesicles; 0.ne child had a fever (39oC) for 1 day about 3 weeks

vaccine, including further studies on the latency of the vac‑

after vaccination. These results offered hope that a live vari‑cine virus and the likelihood of subsequent zoster.

Cella vaccine could be administered with some precautions
to high‑risk children.

Clinical vaccine trials in the U.S. and Europe

Most of the results of these clinical trials were reported in
majorjoumals of the United States (U.S.) and Europe, whichh the beginnlng OfFebruary 1979, a workshop on herpes‑
viruses was held at the U.S. National Institute ofHealth(NIH)
for 3 days. Approximately 200 experts ofpediatric infectious
diseases, virology, and public health section from the U.S.,

drew strong attention of pediatricians, virologists, and those

who were concemed with vaccine production.

Canada and Europeancountries attended the workshop. The

Viewpoints regarding live variceua vaccine aftermain subject was whether or not varicella vaccine should beinitial clinical trials

Various vleWPOints were expressed regarding live varicellaevaluated in climical trials involving high‑risk children. I was
invited, being asked to talk on the details of results of vaccine

vaccine. Philip Brunell (30) raised concems about live vari‑development and its clinical trials in Japan. The last sectionof the workshop was general discussion. Saul Kmgman firstcella vaccine. His main polntS Were aS follows.
1. The vaccine itselfmay cause zoster, however, it willreferred to good short‑termresults with the vaccine, whichtake decades to find out whether or not this is the case.
2. Unfortunately, markers predictive of the behavior of ahe thought deserved to be tested. There was no objection to

3. Immunity a洗er vaccination may not be as long‑lastinghis view. After the workshop, an NIH Collaborative Study
Group was organized (Chief, Anne Gershon of New York
University and later of Columbia University), and clinical
trials were started with live varicella vTccine (Oka strain)

as that after natural infection, thus vaccination may en‑
hancethe risk of the relatively severe disease that fre‑produced by Merck Research LaboratorleS, West Point, Pal ,USA. Many excellent investigations (35‑3 8) were conducted

quently fわllows in adulthood.

by that group･ including clinical reactogemicity, the frequenT

glVen Strain ofVZV with respect to causlng ZOSter havenot been identified.

4. Since naturally occumng varicella canbe severe or evenof household transmission from vaccinated acute leukemlC

fatal in immunocompromised children who are receiv‑

children with rash, and the persistence of immunity. Otherlng SterOids for various chronic conditions and in patients

study groups also conducted climical trials, most of whichwith leukemia, it is not clearwhether a live varicella would

yielded favorable results (39‑43). In Europe, clinical trials

protect these children or cause serious disease,and it will

were conducted with varicella vaccine (Oka strain) prepared

be hard to find out.

by SmithKline RIT, Rixensart, Belgium. In 1983, the expert

committee (Chief, F.T.Perkins) was held at the World HealthOrganization in Geneva to prepare a manuscript entitled

Albert Sabin (3 1) presented the following views on thematters discussed by Brunell:"RequlrementS for the Live Varicella Vaccine". me resulting

1. There is a high probability that live varicella vaccine

virus will cause zoster infrequently; the absence of
lesions and clinical manifestationsinvaccinated children

document was circulated and reviewed by authorities aroundthe world and was finally published in 1985 (44). Meanwhile,
in 1984, the live varicella vaccine (Oka strain) produced byindicates that there is only limited viral multiplications

SmithKline RIT was licensed for administration to high‑risk

and dissemination in仇e body and thus the potential f♭r

2. The lack of markers for zoster is not a contraindication

childreninAustria, Belgium,the Federal Repubhc of Germany,
Ireland, Luxemburg, Portugal, Switzerland and the United

for the testlng Or use Oflive varicella vaccine, live measles

Kingdom. In November 1984, a symposium on active immu‑

only limited (or no) invasion of sensory ganglia.

andrubella vaccines are being used in the absence ofdis‑

nization agalnSt Varicella was held in Munich. The papers

ease specific markers.

presented at this meetlng Were Publishedinthe followlng year

3. The duration of immunityfollowing the injection of a(45). I was personally encouraged to read in this publication,

varicella vaccine is, of course, important, but it can be

Plotkin'S statement (46) that despite a few questions, varicellavaccine appears to have a bright future, and that the work ofdeterm ined.
Stanley Plotkin (32) expressed a viewpoint in opposition toProfessor M. Takahashi, conducted over moro也an 10 years,

Brunell'S, emphasizing that authority, however wellmeaning,deserved praise, as he has persevered in the face of criticism,should not stand in the way of gathering data as long as thebringing medical science to the point where we cancontemplateconsequences weighed at each step. White stresslng the need

血e conquest or another widespread human disease. ｡

for caution, Brunell (33) replied that he wholeheartedly
supported research that would increase the understanding of

Herpes zoster and a live varicella vaccine

virus latency. C. Henry KempeandArLne Gershon (34) statedthat although varicella vaccine might resultineitheranincrease

It has generally been believed that VZV in the skin vesicles

or a decrease in latency, there was a real possibility of thetravels up the sensory nerves to posterior ganglia, where it

51

persists; this seems to be the major route Of virus mlgration.

Thus we made this comparison and the results shed more

Hope‑Simpson (47) noted that the patternof incidence oflight on the latency of vaccine vims in vaccine reclpients. In

zoster on individual sensory ganglia is similar to the distribu‑

a retrospeCtivefollow‑up study of children withacute leukemia,tion of the rash in chickenpox and may bear a direct relation‑

zoster occurred far more frequently in the group that devel‑

ship to it. TTLis observation may explain why sensory ganglia,
and not motor ganglia, are selected f♭r viral lodgment･ As

oped a rash after vaccination (17.1% or 3.13 cases per 100
person ‑years; n=70) than in that without rash (2.4%, or 0.46

mentioned at the beginning Of this review article, a major

cases per 100 persons‑years; n=250) (50‑53) (Table 6). These

question about live varicella vaccine had been whether thevaccine virus becomes latent, resulting in the later develop‑

figures suggested an absence of rash after vaccination isment ofzoster. Since zoster is relatively uncommon in healthy

that the incidence of zoster is loweramOng vaccine recIPlentSchildren, long‑term follow‑up of vaccinated healthy children

than among children who had natural varicella.

closely correlated with a low incidence of zoster, indicatlng

was required to answer this question definitely. However,In 1986, live varicella vaccine produced by the Researchchildren with acute leukemia tend to develop zoster soon

Foundation for Microbial Diseases of Osaka University,

after natural infection. Therefore, it was assumed that careful
withALL would yield valuable insight. Vaccinated leukemic

Osaka was licensed in Japan for use in highrisk children andfor optional use in children at standard risk. In Korea, live
varicella vaccine (Oka strain) was licensed similarly in Japan

children were followed closely for the development of zoster

in 1988.

observation of the incidence of zoster in vaccinated children

and compared with leukemic children who had had natural

varicella.

Further clinical studies in the U.S. particularly

In one study group in Japan, the incidence ofzoster amongon the incidence of ZOSter after vaccination

vaccinated and naturally infected children was 1 5.4% (n=52)
and 1 7.5% (n=43), respectively (48);inanother, the rates wereStudies kom the U.S. have indicated more clearly that the

9.1% (〃=44), and 21.6% (〃=37), respectively (49). Clinicalincidence of zoster after vaccination of leukemic children issymptoms in vaccinated children were usually mild andlower than that after natural infection. Brunell et al. (54)untroublesome, while in the naturallyinfected children in thelatter study group, one had moderateandthe other had severe
symptoms. Some VZV isolates from cases of zoster thatdevelopedinvaccinated patients with ALL were shown to bereported that 1 9 of 26 children with acute leukemia who had

derived from the vaccine virus (20).

body response or to develop chickenpox, therisk of zoster

natural varicella developed zoster, while none of48 vaccinees
did. With adjustment for the duration of observation and theexclusion of vaccinees who failed to have a sustained anti‑

However, all of the individuals studied hadunderlying acutewas still lower amon等vaCCinees (FO･01 7)･ TheinvPstigators

leukemia, and person‑to‑Person variation in their physicalconcluded that there lS nO reason tO Suspect that recIPlentS Of

condition might complicate precise comparisons of thevaricella vaccine are more likely to develop zoster thanincidences ofzoster in the two groups.AsI thought over how

children who have varicella.

we could obtain more definitive evidence on the incidence ofOne comparative study included 84 matched palrS OfU.S.

zoster after vaccination of children with acute leukemia, it

children with underlying acute leukemia. Zoster developed

occurred to methatthe incidence ofzoster should be followedin three (3･6%) of the 84 vTccinated subjects during 2･936

in two groups or children with acute leukemia; one thatmonths of observation (an Incidence of 1.23 casesper 100

developed rash a触r vaccination and onethat did not.Asnoted

person‑years) and in ll (13.1%) of the 84 naturally infected

previously, the major route by which VZV reaches ganglia

subjects during 4.245 months of observation: (an incidence

seems to be alongperipheral nerves from vesicles. If theof3. 1 1 cases per loo person‑years) (36).

incidence of zoster was found to be higher among children

who developed a rash after vaccination than among those who

Further studies by National Institute ofAllergy and Infec‑
tiousDiseases (NIAID) Collaborative Study Group elucidated

did not, then we should be able to predict whether latentclearly that an absence of rash is correlated with a low

infection of vaccine virus would occur in immunized children

incidence ofzoster (55). Of268 vaccinated children with VZVrashes, 1 1 (4. 1%) had zoster. In contrast, there were only twocases of zoster (0.7%) among the 280 vaccinated children

developlng On their reaction to the vaccine.

with no VZV rash (β= 0.02 by x2 test with continuity correc‑tion), The relative risk of zoster in the children who had had

Table 6. Comparison of incidence of zoster in acute leukemic children

a VZV rash was 5.75 (95% confidence interval, I.3‑25.7).

wi血Or without clinical reaction fbllowlng Vaccination

Besides the main mi.gration route (i･e･, via the sens?ry

No. of cases that developed zoster
Year aRer
vacc lnatlOn

Rash (+) after Rash (‑) a洗er

nerve), there may be a mlnOr hematogenous route ofmigratlOn

Tわtal

by virus to the ganglia (56)･ However, no vireTlia 乍ould bevacc i nation vacc inati on

0 1 2 つJ 4llIl ‑

1 2 tJ 4 5

8 つJ 0 0 1

tJ 2 1 0 0

detected in healthy vaccine recipients, while vlremla could‖5101

be detected in cases of natural varicella for several days before

and just after appearance of the rash (57). Therefore, whatever
the route, it seems far less likely for the vaccine virus thanfor wild‑typevirus to become latent in the ganglia,and cause
subsequent zoster.
Total

12/70(17.1%)

Given these results and currentknowledge on the path0‑6/260(2.3%) 18/330(5.5%)

genesis of herpes zoster, we can be convinced that immuni‑
zation with live varicella vaccine would lead to a slgnificant

Tわtal observation

period (month)

3.217

10.8943.13

0.46

Casesper
1 00 person.years

decrease in the incidence of herpes zoster.

In 1995, live varicella vaccines (Oka strain) (produced by
Merck Research Laboratories) were licensed forthe universal(&om ref. 53)

52

immunization of healthy children in the U.S.

type 2. Nature, 233, 45‑50.
1 0. Takahashi, M. and Yamanishi, K. (1974): Transformationof hamster and human embryo cells by temperaturesensitive mutants of herpeS simplex virus type 2. Virology,

Recent progress on varicella vaccine

Since the frequency and severityofherpes zoster increases

61, 306‑311.

with aging (58)･ and since VZV‑sp.ecific T cell‑mediatedll. Gelb, L., Huang, J. J. and Vellinghof, W. J. (1980):

imTlunity(CMI) decreases with age, 1t Was hypothesized that

Varicella‑zoster virus transformation of hamster embryo

cells. J. Gen. Viro1., 51, 171‑177.

actlVe immunization of older persons would boost血eir CMI

against VZV and thereby decrease the frequency or severity

12. Gelb, L. and Dohner, D. (1984): Varicella‑zoster viruS‑(or both) orhe叩eS ZOSter in vaccinees (59). Levin et al. (60)induced transfbmation or mammalian cells in vitro. ∫.

reported in their 6‑year follow‑up study of 130 vaccinated

Invest. Demato1., 83, 77S‑81S.
13. Caunt, A. E. (1963): Growth ofvaricella‑zoster virus inpersons ≧ 55 years of age, although the frequency ofherpes‑
zoster like clinical events was within the expected range fわrhuman thyroid tissue cultures. Lancet, 2, 982‑983.

this age cohort, the number of lesions was small, there was

14. Caunt, A. E. and Taylor‑Robinson, D. (1964): Cell‑freevaricella‑zoster virus in tissue culture. J. Hyg. (Lond.),very little palm, and血ere was no post‑herpetic neuralgia.

On the basis of their results, a large scale immunization

62, 413‑424.

15. Brunell, P. A. (1967): Separation of infeCtious varicella‑trial for nearly 40,000 persons over 60 years of age, with halfof them are placebo group, has been golng On in the U.S.
uslng high titered varicella vaccine by the support of NIH.

zoster virus from human embryonic lung fibroblasts.

Virology, 3 1 , 732‑734.

16.Asano, Y. andThkahashi, M. (1978): Studies on neubTaliza‑

The result will come out in 314 years.

Our recent study has demonstrated that the administration

tion or varicella‑zoster vims and serological follow‑up
ofcases ofvaricella and zoster. Biken J., 21 , 15‑23.

or booster doses of varicella vaccine to elderly individuals

produces enhanced immunityto VZV, as indicated by levels
ofanti‑VZV antibodies and skin reactivityto VZVantigen (6 I ).
We are hoping that live varicella vaccine would be of help

17. ¶lkahashi, M., Otsuka, T., Okuno, Y, Asano,Y., Yazaki,

T. and Isomura, S. (1974): Live vaccine used to preventthe spread of varicella in children in hospital. Lancet, 2,1288‑1290.

for prevention of herpes zoster, particularly for post herpetic

18. Takahashi, M., Asano, Y., Kamlya, H., Baba, K. andneuralgia.

Yamanishi, K. (1 98 1 ): Active immumization for varicella‑zoster virus. p.414‑43 1. In Nahmias, A. J., Dowdle, W.R.

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55