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AMER ICAN JOU RN AL OF EPIDEMIOLOGY Vol. 119, No. 6Copyright O 1984 by The Johns Hopkins University School of Hygiene and Public H ealth Printed in USA.All rights reserved

GUILLAIN-BARRE SYNDROME AND ITS RELATION SHIP TO SWINEINFLUENZA VACCINATION IN MICHIGAN, 1976-1977

JOE L G. BREMAN1 AND NORMAN S. HAYNER2

Brem an, J. G. (CDC , Atlanta, GA 30333), and N. S. Hayner. Guillaln-Barre syn-drome and Its relationship to swine Influenza vaccination in Michigan, 1976-

1977. Am J Epidemiol 1984;119:880-9.Active surveillance to detect all patients with Gulllaln-Barre syndrome whohad had onset of Illness from July 1, 1976 through April 30, 1977 was under-take n In M ichigan after Indications that the syndrome might be associated withthe National Influenza Immunization Program of 1976-1977. Hospital recordroom l ibrar ians , neurologis ts , and neurosurgeons reported the greatestnumber of cases; coded hospital discharge records were the best means ofascertaining case occurrence. This differed from national surveillance, whichrelied essen tially o n repo rts that neurologists and other clinicians sent to stateepidemiologists and then to the Centers for Disease Control; hospital dis-charge lists were not systemlcally reviewed nationally. A total of 79 of theMichigan cases were in persons who had not received swine Influenza vaccine,while 46 cases were in persons who had received It. For unvacclnated adults,the Incidence of Gulllaln-Barre syndrome during the 10-month surveillanceperiod was 0.36 cases per 10 s person-weeks; for adults with onset within sixweeks of vaccination, It was 2.31 cases per 10 6 person-weeks. After six weekspost-vaccination, the rate decreased to 0.17 cases per 10 6 person-weeks. Theattributable risk for acquiring Gulllaln-Barre syndrome within six weeks afterreceiving swine Influenza vaccine was 11.70 cases per 10 s persons vaccinated.

autoimmune diseases; Gulllaln-Barre syndrome; polyneuritis; swine influ-enza vaccine

Received for publication December 20, 1982 and Dr. Ke nne th R. Wilcox, Michigan D epa rtm ent ofin final form Feb ruar y 6, 1984. Public He alth, and Dr. Law rence B. Schonberger,

1 Div ision of Field Ser vice s, Epidem iology Pro- Cen ters for Disease Control (CDC), for review andgra m Office, Ce nters for Disease Con trol, Atl anta , support of the study; Den nis J. Breg ma n, Robert C.GA. Holm an, and Rose Ka min sky (CDC) for statistic al

2 Bu rea u of Labo ratory a nd Epidemiologic Ser- assistance; Donald L. Eddins, Dr. Alan R. Hinm an,vices, Michigan Departm ent of Public He alth, P.O. Joh n A. Orris, and Dr. Ka thryn R. Shands (CDC)Box 30035, Lansing, MI. for comm ents on the ma nus crip t; Neil Brog an,

Send rep rint requests to Dr. Brem an at the Ma- Diane Knott, Elaine N euha us, and Debbie Nixonlaria Branch, Division of Parasit ic Diseases, Center for assistance w ith the m anu scrip t; and p art ici-for Infectious Diseases, CDC, Atla nta, GA 30333. patin g physicians , hosp itals, local hea lth dep art-

The auth ors than k Ned C. Rasm ussen, Cleland men ts, physical thera pists, and the Michigan StateChild, and H arr y McGee, Michigan D epa rtm en t of Medical Society for the ir cooperation dur ing the in-Pub lic H ea lth , for assistance with data collection; formation ga the rin g pha se of the project.

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GUILLAIN-BARRE SYNDROME IN MICHIGAN, 1976-1977 881

In early December 1976, it was ob-served that the administration of killedswine influenza vaccine (A/New Jersey/1976/H1N1) appeared to be associatedwith an excess incidence of Guillain-Barr6 syndrome. This association re-sulted in cessation of the National Influ-enza Immunization Program on De-cember 16, 1976. National surveillancewas established in mid-December 1976 bythe Centers for Disease Control to detectpersons with the syndrome who had haddisease onset between October 1, 1976,the beginning of the National InfluenzaImmunization Program, and Janu ary 31,1977, to determine if there was an as-sociation between the influenza vaccina-tion and the Guillain-Barre syndromecases (1).

As part of the national surveillanceprogram, we established a system inMichigan to detect cases with onset fromJuly 1, 1976, to June 30, 1977. The pur-pose was to obtain detailed information

on the frequency of the syndrome in Mich-igan over th is extended period, to describeits epidemiology in terms of certain de-mographic variables and seasonality, andto discern any association between theswine influenza vaccination campaignand case onset.

MATERIALS AND METHODS

To be included in this study, a case of

Guillain-Barr6 syndrome had to havebeen diagnosed by a physician and tomeet a ll of the following criteria (2): bi-lateral muscle weakness of the lowermotor neuron type with or without cra-nial nerve or sensory abnormalities;acute or subacute onset and evolution ofsigns and symptoms; and absence of otherconditions such as diabetes mellitus, al-coholism, neoplasia, etc., tha t could cause

the polyneuropathy. Cases who developedresidual neurologic deficits ("chronic"Guillain-Barr6 syndrome) were includedonly if they had the requisite early signsand symptoms. Detailed clinical and epi-

demiologic information was recorded on astandardized form developed by the Cen-ters for Disease Control for national sur-veillance. Each reported case was dis-cussed with the primary-care physician,the consulting neurologist, or both, toconfirm the diagnosis. There was fre-quently a delay of several weeks before apatient with neurologic disease was di-agnosed definitely as having the syn-drome or before the case was reported;therefore, almost all of the patients withthe syndrome had passed the peak of theirillness when their case was recorded atthe Division of Epidemiology, MichiganDepartment of Public Health.

Surveillance for Guillain-Barre syn-drome began in Michigan in mid-De-cember 1976 in response to the alert bythe Centers for Disease Control that thesyndrome might be associated with vac-cination with the swine influenza vac-cine. The f irst action was to contact a fewneurologists working at the larger med-ical centers to determine if there were in-creased numbers of cases. Between De-cember 20, 1976 and Ju ne 30, 1977, neu-rologists and neurosurgeons in Michiganwere canvassed four times by telephone,letter, or both. Record room librarians atall Michigan hospitals were contactedthree times between January21 and June30, 1977. Discharge diagnoses datingback to July 1, 1976 were reviewed. Al-

most all hospitals in Michigan code theirhospital discharge diagnoses using thecodes published by the Commission onProfessional and Hospital Activities (3).The Code H-ICDA 354 includes the Guil-lain-Barre syndrome, active infectiouspolyneuritis, multiple peripheral neuritis(acute, infective), and acute ascendingspinal paralysis. The 1,006 registeredphysical therapists were contacted by

letter in February 1977 and asked toremit a pre-addressed form to the statehealth department indicating whether ornot they had treated patients with thesyndrome. Requests for reports on Guil-

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882 BREMAN AND HAYNER

Iain-Barr6 syndrome were included in thebulletin of the Michigan State MedicalSociety, and local departments of healthwere asked to detect cases and reportthem to the state health department.Local health departments had alreadybeen doing surveillance for vaccine-asso-ciated complications since the beginningof the swine influenza program in October1976.

The final surveys were done in June1977 and investigations of cases werecompleted and the files closed withinJuly, as the field investigators' contractsended at tha t time. Some cases with onsetin May or June presumably were notfound; therefore, while all cases duringthe surveillance period are reported, de-tailed analyses are confined to the 10-month period from Ju ly 1, 1976, to April30, 1977. Persons vaccinated in Michiganbut who had onset of the syndrome inother states (including one not detecteduntil 1979) are not included because in-formation on them is inadequate for anal-ysis; there were no patients detected whowere vaccinated elsewhere but who werehospitalized in Michigan.

Incidence rates of cases per one millionperson-weeks were calculated accordingto vaccine status, age, and sex. The data

bases for these calculations were inter-polated population estimates, weekly vac-cination totals and age-sex reports ofvac-cinations, and Guillain-Barr6 syndromecase counts. Population estimates weredeveloped by application of sex ratiosfrom the most recent state estimates (4)to US Bureau of the Census es timates forMichigan, by age(5). Chi-square analyseswere used to compare the incidence ratesin various vaccinated and unvaccinatedgroups (6).

RESULTS

Hospitals had the highest rate of re-sponse (table1). All of the major hospitalsin the state responded, representing over95 per cent of patient beds. On the initialcase identifications, the hospital surveysdetected 36 per cent, neurologists andneurosurgeons contributed 35 per cent,and physical therapists added 5 per cent.The remaining 24 per cent of the caseswere reported by primary care physi-

cians, local health officials, and patientsor their families.Use of the four surveillance methods re-

sulted in some persons being reportedmore than once, indicating that virtuallyall of the cases that occurred from July 1,1976 to April 30, 1977 were probably de-

TA B L E 1

Groups surveyed to detect patients with Guillain-Barri syndrome, Michigan, 19761977

Group contacted Beginningof survey Type of surveyNo.

contacted* responding

to survey

Neurologists/neurosurgeons

Hospitals

Physicaltherapists

December 20, 1976*February 3, 1977March 28June 30

January 21March 28June 30

February 3

TelephoneQuestionnaireQuestionnaire

Questionnaire,telephone

Questionnaire, visitQuestionnaire, visitQuestionnaire, visit

Questionnaire

142

375

1006

>9 02736 t

>75

8287 t

>90

37

* Partial survey done as a preliminary canvas.t Contacted only non-respondents to previous survey.

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tected. Over 300 possible cases werescreened, and over half were excluded onthe basis that they did not meet the casecriteria. Excluded patients usually had adiagnosis that had been changed by thephysician, signs that did not progress, oranother confounding diagnosis, such asalcoholism. All cases in th is group of sus-pect Guillain-Barr6 syndrome were fol-lowed until exclusion could be done con-fidently. Vaccination status was irrele-vant when assessing exclusion of a case.However, when the clinical details wereconsidered, the physicians and classifying

epidemiologists did know whether or nota patient had received swine flu vaccine.The per cent of the patien ts who were vac-cinated (and unvaccinated) and who didnot meet the case definition is unknown.

A total of 132 cases were confirmed ashaving onset between July 1, 1976 andJune 30, 1977. Of these, 84 persons hadreceived no vaccine and are designated asgroup A; 48 persons had received swine

influenza vaccine, ofwhom eight had hadonset of the syndrome before vaccinationand were designated group B. This lattergroup was considered independently ofgroup A in the analyses; they may havebeen a selected group because of subse-quent vaccination (e.g., they sought vac-cination because of a special hea lth sta tusincluding a predisposition to Guillain-Barr6 syndrome). Among the persons who

received the vaccine, there w as a d istinctincrease in cases within six weeks aftervaccination; the greatest number oc-curred during weeks 2-4 after vaccina-tion (figure 1). Incidence am ong vaccineesin the period before vaccination, and7 +weeks after it, was much lower than thatin weeks 1-6 post vaccination. The otherGuillain-Barr6 syndrome categories aredefined as follows: groupC, onset of symp-toms w ithin six weeks of vaccination; andgroup D, onset of symptoms more than sixweeks after vaccination.

The approximately 2,300,000 persons

vaccinated during October 5-December16, 1976, represent about 25 per cent ofMichigan's population (table 2). Over 80per cent of those vaccinated during thecampaign received their vaccine by theend of November 1976, so that by the endof April 1977, they had been under sur-veillance for at least five months.

The number of unvaccinated personswho had onset in May and June 1977

showed a decrease compared to the pre-vious 10 months (figure 2). As noted, thismay have been due to less complete as-certainment; therefore, the five unvacci-nated cases and two vaccinated cases thatoccurred in these months are excludedfrom subsequent analysis. The frequencyof onsets in unvaccinated adults rangedfrom 4-12 for each month from July 1976through April 1977. An increased fre-

UJ

- 5 H

CASE WITH ONSET D July 19 76 -A pr il 1977 nMay -June 1977

10-1

n m n n20 15 10 5 0 5

WEEK(S) BEFORE fVACCINATION

n10 15 20

WEEK(S) AFTER

rp25 3 0

FIGURE 1. Guillain-Barr6 syndrome cases in persons vaccinated, by week of onset before or after swineinfluenza vaccina tion, Michigan, Ju ly 19 76 -Ju ne 1977. (No te the first week after vaccination beginswith the day of vaccination and continues until the sixth day afterward.)

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TA B L E 2

Estimated population in Michigan by age, sex,and swine influenza vaccination status,July 1976-AprU 1977*

Age (years)

0-17

18-44

45-64

65 +

Subtotal18 +

Total

Sex

MalesFemalesMales + females



Males

FemalesMales + females


MalesFemalesMales and females

Not vaccinated

1,418,0001,365,0002,783,000

1,217,0001,214,0002,431,000

523,000638,000

1,061,000

214,000

290,000504,000

1,954,0002,042,0003,996,000

3,372,0003,407,0006,779,000

Vaccinated

51,72547,53899,263

574,300605,820

1,180,120

347,752371,504719,256

146,366

190,615336,981

1,068,4181,167,9392,236,357

1,120,1431,215,4772,335,620

Total

1,469,7251,412,5382,882,263

1,791,3001,819,8203,611,120

870,752909,504

1,780,256

360,366

480,615840,981

3,022,4183,209,9396,232,357

4,492,1434,622,4779,114,620

* See references 4 and 5.

quency of cases occurred in September-October 1976 comparedto preceding andsubsequent two-month periods{p < 0.05)(figure 2). This difference remainedsig-nificant (p < 0.05) even if the class Bcases were included with class A cases bymonth of onset.

Apart from one vaccinated case withonset in October, a total of 30 cases in thevaccinated population occurredin No-vember-December 1976.A decrease incases was observed in the unvaccinatedgroup in these months (figure 2).In twoperiods, November-December 1976 andJanuary-April 1977,the following num-bers of adult cases occurred: the vacci-nated group had30 and seven cases (ratio4.3) and the unvaccinated nine and 19cases (ratio 0.5), respectively. The differ-ence in these ratios is highly significant(p < 0.001) indicating furtherthe associ-ation between vaccinationand onset in

November-December but not for Jan-uary-April .

In computing, rates of Guillain-Barr6syndrome denominators were drawn fromtable 2, which indicates the population ofMichigan which remained unvaccinatedduring the swine influenza program,andthat which received a vaccination.TheAppendix tab le gives the person-weeks ofexposure for each group used to computethe rates shown in table 3. The incidenceincreases with agefor group A, primarilydue to the rise in rate s formales.The rateamong group B adults was 0.19 cases per106 person-weeks; for category D it was0.17 cases per 106 person-weeks. Thesewere not significantly less than thatforunvaccinated adults in group A, 0.36cases per 106 person-weeks.

Group C had an overall rate of 2.21cases per 106 person-weeks. There isa sig-nificant difference betweenthe attack

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GUILLAIN-BARRfi SYNDROME IN MICHIGAN, 1976-1977 885

20 nco

g. 15'

S.o

5 10

inS io

5-

UNVACCINATED

S < 18 Yeors Old

O 18 Years Old

J'A'S'O'ND JFMAMJ1976 1977

VACCINATED(all adults)Onset BeforeVaccine

Onset in Weeks 1-6After Vaccine

Onset in Weeks 7 +After Vaccine

0

FIGURE 2. Cases of Guil lain-Barr6 syndrome byswine influenza vaccine status and month of onset,Michigan, 1976-1977.

rates in the vaccinated persons in groupC and those for the other groups; withinsix weeks after vaccination the incidencefor adults, 2.31 per 106 person-weeks,is significantly greater than for the un-vaccinated group A, or for the other vac-cinated groups B or D. The risk attribut-able to swine influenza vaccination for anadult 2=18 years acquiring the syndromewithin six weeks after vaccination, was

11.70 cases per 106

persons vaccinated(2.31 x 6 weeks - 0.36 x 6 weeks).Within each group there were no sta-

tistical differences between attack rates

among sexes. The highest rates were forpersons aged 4 5- 64 years. There were nocases in persons less than 18 yea rs of agein groups B, C, or D; therefore, thoseunder 18 years old were not included insubsequent calculations.

In unvaccinated children


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TABLE 3

Frequency of Guillain-Barri syndrome by swine influenza vaccine group, age, and sex, M ichigan,July 1976-April 1977

Age(years)

0 - 1 7

1 8 - 4 4

4 5 - 6 4

65 +

Subtotal18 +

Total

Sex







ANot

vaccinated

No.

106

16

141630

127

19

95

14

352863

453479

Rate*

0.160.100.13

0.270.300.28

0.530.300.41

0.970.400.64

0.410.320.36

0.310.230.27

Vaccine group

BOnset beforevaccination

No.

000

213

123

112

448

448

Rate*

(0.19)(0.09)0.13

(0.15)(0.29)0.22

(0.36)(0.28)(0.32)

0.200.180.19

0.190.170.18

COnset1- 6 weeks

aftervaccination

No.

000

41014

68

14

123

112031

112031

Rate*

1.162.751.98

2.873.593.24

(1.14)(1.75)1.48

1.722.852.31

1.642.742.21

No

000

022

112

213

347

347

DOnset7 + weeks

aftervaccinationi. Rate*

(0.18)(0.09)

(0.15)(0.15)(0.15)

(0.74)(0.28)0.48

0.150.180.17

0.140.180.16

* Rate per 106 person-weeks. Numbers in parentheses are derived from numerators with


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VACCINE

None 63

- After Onset 8

0-41 Days before Onset 31

* 4 2 + Days before Onset 7

50 100 150 200 250 Km

FIGURE3. Geographical distrib ution of adu lts (*18 ye ars old) with Gu illain-Ba rre syndrom e in Michigan,July 1976-April 1977.

TABLE 4

Rates, by manufacturer and sw ine influenzavaccine type, for Guillain-Barre' syndrome cases

within six weeks of vaccination in Michigan,

1976-1977

Manufacturer Cases No. ofused*Casea/100,000

W. (Split)X. (Split)Y. (Whole)Z. (Whole)UnknownTotal

178

132

31

183,250864,930547,260

1,325,830

2,911,270

0.50.81.51.0

1.1

* Doses distributed less doses returned.

with, clinicians and physical therapists.This was a more comprehensive and vig-orous surveillance effort than that usednationally in part because of the re-sources available.

Cases and incidence rates of Guillain-Barr6 syndrome studied nationwide werederived largely from contact with neurol-ogists, bu t since the period of surveillanceonly continued to the end of Ja nu ary 1977and was relatively limited in scope it wasdifficult to appreciate the secular trend inthe United States. Part of the reportingdifficulty was that Guillain-Barr6 syn-drome is not a reportable disease. Evenso, an intense effort, coordinated at thenational level, was needed to determinewhether a statistical association existedbetween the syndrome and swine influ-enza vaccine.

In Michigan, six weeks after vaccina-tion, the rate of the syndrome for vacci-nated adults dropped below that of thebackground level of Guillain-Barr6 syn-

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drome in the entire unvaccinated popu-lation and in adults. These backgroundrates a re higher than the rate reported inIsrael (8), 0.75 per 105 person-years (0.14

cases per 106

person-weeks), where ascer-tainment of the syndrome was done withthe aid of a National Registry of Neuro-logical Disease. Reviews of other popula-tion-based studies of the syndrome (9,10)cite rates of between 0.6 and 1.9 cases per106 person-years (0.12-0.36 cases per 106

person-weeks). These studies, however,came from areas where Guillain-Barresyndrome was not a reportable disease,

included few cases (from 3-40), and cov-ered long periods of time (from 5-42years). Some of these reports do not de-scribe the criteria used for defining cases.

The Centers for Disease Control hasmore recently surveyed a sample of theAmerican College of Neurology to detectGuillain-Barr6 syndrome cases that oc-curred from Jan ua ry 1978 through March1979 (11). A crude attack rate of 0.47

cases per 105

person-years (0.09 cases per106 person-weeks) was found. This 1979study was a good practical way to detectthe approximate occurrence of the syn-drome in populations since the NationalInfluenza Im m uniza tion Prog ram of1976. However, the relatively low attackrate in the study may indicate that phy-sicians are not reporting all cases of thesyndrome and that hospital-based sur-

veillance, as done actively in Michigan,may be the best method to detect severeneurologic disease occurring at low fre-quency. Minor increases in frequency inJa n ua ry -M ar ch 1978 and November1978-January 1979 were observed, andwere probably due to increased surveil-lance during these periods.

The M ichigan study does not perm it in-terpretation of the mechanism that

caused the high risk for those developingGuillain-Barre syndrome within sixweeks after vaccination. Previous reports(12, 13) have indicated th at the syndromeis associated with antecedent infections

and that onset follows the infectious dis-ease, particularly respiratory illness, byabout 2-3 weeks.

In 1978-1979, 12.5 million persons inthe U nited S tates received influenza vac-cine which did not contain the swine in-fluenza component; the relative risk thata person would acquire Guillain-Barr6syndrome within eight weeks after he orshe had received the vaccine was 1.4 (95per cent confidence interval, 0.7-2.7)(14). This was not in excess of what wouldbe expected and was significantly lessthan the relative risk of 6.2 seen in the

same period following administration ofswine influenza vaccine to the entire USpopulation (1). During 1978-1982, 12.4-19.9 million influenza immunizationswere given annually (15). Passive sur-veillance has not detected an excess ofGuillain-Barr6 syndrome cases associatedwith these vaccinations. Indeed, becauseof the low rates and the high cost of caseascertainment, national surveillance for

Guillain-Barr syndrome, as done be-tween 1976 and 1979, has not been con-tinued.

The unvaccinated population in ourstudy had a mildly increased incidencewith age. This might indicate that priorsensitization is needed to trigger an au to-immune response. Children aged 14-17years showed increased rates of the syn-drome during January-April. Influenza,

or other respiratory agents known to beassociated with onset of the syndrome,might be responsible. In contrast, the ratefor adults was greater in September andOctober than for other bimonthly periods,and we have no explanation for this in-creased ra te. No definite seasonal pa tternof Guillain-Barr6 syndrome emergedfrom this study nor has previous work in-dicated seasonal trends (8-10, 14, 16).

More precise epidemiologic informationon neurologic syndromes of public healthimportance that occur at low rates couldbe obtained if these diseases were madereportable. Improved reporting would

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help to define associations of diseaseswith events more promptly and precisely.

REFERENCES

1. Schonberger LB, Breg ma n DJ, Sullivan-BolyaiJZ, et al. Guillain-Barre syndrome followingvaccination in the National Influenza Immu-nization Program, United States, 1976-1977.Am J Epidemiol 1979;110:105-23.

2. Masucci EF, Kurtzke JF. Diagnostic criteria forthe Gul la in-Barr6 syndrome. J Neurol Sci1971;13:483-501.

3. Commission on Professional and Hospital Ac-t ivi t ies, Hospital Adaptation of InternationalClassification of Disea ses (H-ICDA ). Vol.1 (tab-ular list), Ann Arbor, 1968.

4. Michigan Depar tm ent of M anagem ent andBudget, Population Projections for Michigan to

the Year 2000: Sum mary re port state, regionsand counties, Lansing, Michigan. ISC Publica-tion Series 1978-1, 14 pages.

5. US Department of Commerce, Bureau of theCensus. Current population reports, populationestimates and projections, estimates of the pop-ulatio ns by state s by age. July 1, 1971 to 1979,Series P-25, No. 875,1980. Washington,DC: USGPO, 1980:4-5.

6 . Snedecor GW, Coch ran WG. Sta t i s t ica lMethods. 6th ed. Ames, IA: Iowa Universi tyPress, 1967.

7. Langm uir AD, Bregman DJ, Ku rland LT, et al.An epidemiologic and cl inical evaluation ofGuillain-Barre syndrome reported in associa-

tion with the administration of swine influenzavaccines. Am J Epidemiol 1984;119:841-79.

8. Soffer D, Feldman S, Alter M. Epidemiology ofGuillain-Barr6 syndrome. Neurology 1978;28:686-90.

9. Schonberg BS. Epidemiology of Guillain-Barresyndrome. In: B. Schonberg, ed. Advances inneurology. New York: Raven Press, 1980:249-58 .

10. Schonberger LB, Hurwitz ES, Katona P, et al.Guillain-Barre syndrome: its epidemiology andassociat ion with influenza vaccination. AnnNeurol 1981;9(suppl):31-8.

11 . Center for Disease Control. Guillain-Barre syn-drome surveillance report: January 1978-March1979. Atlanta, GA: CDC, October 1980, 1-13.

12 . Melnick SC, Flewett TH. Role of infection in theGuillain-Barr6 syndrome. J Neurol NeurosurgPsychiat 1964;27:395-407.

13. Sliman NA. Outbreak of Guil lain-Barre syn-drome associated with water pollution. Br MedJ 1978;l:751-2.

14 . Hurwitz ES, Schonberger LB, Nelson DB, et al.Guil lain-Barre syndrome and the 1978-1979influenza vaccine. N Engl J Med 1981;304:1557-61.

15. Centers for Disease Control, Biologies Surveil-lance, Report 86, Jan uar y-J un e 83, US D epart-ment of Health and Hum an Services, US PublicHealth Service, 1983.

16. Kennedy RH , Danielson M A, Mulder DW, et al.Guillain-Barre syndrome: a 42-year epidemio-logic and cl inical s tudy. Mayo Clin Proc1978;53:93-9.

APPENDIX TABLE

Risk denom inators in millions of person-wee ks for Michigan population under surveillance, July 19 76through April 1977, by influenza vaccination status, age, and sex

Age(years) Sex

ANo t

vaccinated

BVaccinees before

vaccination

CWeeks 1-6

aftervaccination

DWeeks 7 +

aftervaccination

0 - 1 7

18-44

4 5 - 6 4

65 +

Subtotal18 +

Total







61.659.3

120.9

52.852.7

105.6

22.723.446.1

9.312.621.9

84.888.7

173.5

146.4147.9294.4

0.980.901.87

10.8311.4222.25

6.567.01

13.56

2.763.596.35

20.1522.0242.17

21.1222.9244.04

0.310.290.60

3.453.637.08

2.092.234.32

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