Immunity Against Infectious Diseases: Predictive Value of Self‐Reported History ofVaccination and Disease • Author(s): Andrea Trevisan , MD; Clara Frasson , SA; Marta Morandin , SA; Michela Beggio ,MD; Alberto Bruno , MD; Elisabetta Davanzo , MD; Livio Di Marco , MD; Livio Simioni , MD;Guglielmo Amato , MDSource: Infection Control and Hospital Epidemiology, Vol. 28, No. 5 (May 2007), pp. 564-569Published by: The University of Chicago Press on behalf of The Society for Healthcare Epidemiologyof AmericaStable URL: http://www.jstor.org/stable/10.1086/516657 .

Accessed: 16/05/2014 05:50

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact support@jstor.org.

.

The University of Chicago Press and The Society for Healthcare Epidemiology of America are collaboratingwith JSTOR to digitize, preserve and extend access to Infection Control and Hospital Epidemiology.

http://www.jstor.org

This content downloaded from 194.29.185.222 on Fri, 16 May 2014 05:50:27 AMAll use subject to JSTOR Terms and Conditions

infection control and hospital epidemiology may 2007, vol. 28, no. 5

o r i g i n a l a r t i c l e

Immunity Against Infectious Diseases: Predictive Valueof Self-Reported History of Vaccination and Disease

Andrea Trevisan, MD; Clara Frasson, SA; Marta Morandin, SA; Michela Beggio, MD;Alberto Bruno, MD; Elisabetta Davanzo, MD; Livio Di Marco, MD; Livio Simioni, MD; Guglielmo Amato, MD

objective. To determine whether self-reported history of disease and/or vaccination is predictive of immunity against hepatitis B,varicella, rubella, mumps, and measles.

design. The seroprevalence of viral antibodies and the predictive value of a self-report questionnaire were determined for 616 paramedicalstudents who matriculated into Padua Medical School (Padua, Italy) during 2003-2005.

results. The majority of subjects (86.9%) remembered being vaccinated against hepatitis B but had no recollection of disease. Amongvaccinees, 1.5% showed markers of previous infection, 6.7% tested negative for anti–hepatitis B virus surface antigen (anti-HBsAg) antibodies,and 91.8% tested positive for anti-HBsAg. Self-reported vaccination history had a positive predictive value of 93.2% for test results positivefor immunity against hepatitis B. Immunity against varicella (93.7% of subjects) and rubella (95.5%) was high, compared with immunityagainst mumps (79.9%) and measles (83.1%). In addition, results of tests for detection of immunity against mumps and measles wereequivocal for more than 7% of subjects, probably because their vaccination regimen was not completed. Self-reported histories of varicelladisease and rubella disease and vaccination had high positive predictive values (greater than 98% each) for testing positive for antiviralantibodies, compared with self-reported histories of mumps disease and vaccination and measles disease and vaccination; however, highpositive predictive values were observed for self-reported histories of mumps only (92.0%) and measles only (94.7%).

conclusions. The self-report questionnaire used in this study did not accurately predict immunity against 5 transmittable but vaccine-preventable diseases. A complete serological evaluation of healthcare workers, followed by vaccination of those with negative or equivocalresults of serological tests, is an appropriate measure to decrease the risk of infection in this population.

Infect Control Hosp Epidemiol 2007; 28:564-569

From the Department of Environmental Medicine and Public Health, University of Padua, Padua (A.T., C.F., M.M., M.B., A.B., E.D., L.D.M.), and theService of Preventive Medicine for Healthcare Workers, Feltre (L.S.) and Mirano (G.A.), Italy.

Received May 3, 2006; accepted August 24, 2006; electronically published April 12, 2007.� 2007 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2007/2805-0009$15.00. DOI: 10.1086/516657

Healthcare workers are at risk of acquiring transmissible in-fectious diseases. For example, before the use of hepatitis Bvirus (HBV) vaccine, the risk of infection for healthcare work-ers was 3-5 times that of the general population; the decreasedrisk has been attributed to the use of the vaccine, rather thanto the use of standard precautions.1 In addition, assumingthat only 3.5% of measles cases are transmitted in a medicalsetting, the risk of infection for healthcare workers is 13 timesthat for the general population2,3; during a worldwide epi-demic of measles during 1985-1991, approximately 60% ofthe adults who acquired the disease were healthcare workers.4

For healthcare workers, the Centers for Disease Controland Prevention (CDC) accepts as evidence of immunity tomeasles, mumps, and rubella documented receipt of virusvaccine, laboratory evidence of immunity, a date of birthbefore 1957, or physician-diagnosed illness5,6; a documentedmedical history of infection or results of serological tests areconsidered to be evidence of immunity to varicella.7 Never-theless, an analysis of the results of serological tests for measles

did not validate exclusion of persons born before 1957 fromimmunization programs because of the significant frequencyof seronegativity and disease among these individuals.8

It has been stated that all healthcare workers new to ahealthcare facility should be screened for immunity to vac-cine-preventable diseases within 10 working days after start-ing their job.9 A rate of immunity greater than 94% is nec-essary to prevent the transmission of viruses.10

Serological testing for viral hepatitis and for the pathogenscausing exanthematic disease during childhood is part of theprotocol used by the Department of Environmental Medi-cine and Public Health at Padua University Medical School(Padua, Italy) for health surveillance of students pursuing aparamedical degree, but it is expensive. For this reason, asimple, self-report questionnaire was prepared and admin-

istered to determine whether self-reported history of diseaseand/or vaccination is predictive of immunity against hepatitisB, varicella, rubella, mumps, and measles.

This content downloaded from 194.29.185.222 on Fri, 16 May 2014 05:50:27 AMAll use subject to JSTOR Terms and Conditions

self-reported vaccination and disease history as a predictor of immunity 565

table 1. Self-Reported History of Disease and Vaccination andResults of Serological Tests for Detection of Viral Antibodies

Disease

Self-reportedhistory, % of subjects

Test result,% of subjects

Disease Vaccination PositiveNegative

or equivocal

Hepatitis B 0 86.9 2.6; 81.3a 16.1Varicella 85.2 1.0 93.7 6.3Rubella 28.6b 62.7 95.5 4.5Mumps 45.1c 32.0d 79.9e 20.1Measles 31.5b 61.5 83.1e 16.9

note. Self-reported data were collected by a questionnaire completedby 616 paramedical students who matriculated into Padua UniversityMedical School (Padua, Italy) during 2003-2005. Hepatitis B and varicellavaccination history were excluded from statistical analysis because hepatitisB vaccination is mandatory and because varicella vaccination is unreliable.See Methods for definitions of positive, equivocal, and negative test results.a Data are percentage of subjects positive for markers of previous infection(ie, anti–hepatitis B virus core antigen antibodies and hepatitis B virussurface antigen [HBsAg]); percentage positive for markers of previousvaccination (ie, anti-HBsAg antibodies).b vs history of varicella.P ! .001c vs history of varicella and vs history of rubella and measles.P ! .001d vs history of vaccination against rubella and measles.P ! .001e vs tests positive for antibodies against varicella virus and an-P ! .001tibodies against rubella virus.

methods

A European Union directive (90/679/CEE) and an Italianlegislative decree (626/94) require health surveillance of allworkers exposed to chemical, physical, and biological risk. Inaccordance with the Italian law, 616 students taking coursesin the paramedical degree program at Padua University Med-ical School during 2003-2005 underwent health surveillanceimmediately after matriculation. A simple, self-report ques-tionnaire was prepared and administered to all of the stu-dents. The questionnaire requested data on demographiccharacteristics, as well as history of disease and vaccinationfor hepatitis B and the following exanthematic diseases duringchildhood: varicella, rubella, mumps, and measles. After-wards, serological tests to detect antibodies against HBV andagainst the pathogens causing these exanthematic diseaseswere performed.

Levels of HBV antibodies and antigens were determinedby means of enzyme immunoassays (Sorin [for the HBV eantigen {HBeAg} and antibody] and Organon Teknika [forthe other HBV antigens and antibodies]). A concentration ofat least 10 IU/L of anti-HBV surface antigen (anti-HBsAg)antibodies was considered to be protective against hepatitisB. Anti–varicella virus, anti–rubella virus, anti–mumps virus,and anti–measles virus immunoglobulin G antibody levelswere measured by means of the Enzygnost enzyme immu-noassay (Dade Behring). Antibody levels indicating a positivetest result were defined as greater than 100 IU/mL for varicellavirus, greater than 10 IU/mL for rubella virus, and greaterthan 0.3 IU/mL for measles virus. Antibody levels indicatinga negative test result were defined as less than 50 IU/mL forvaricella virus, less than 4 IU/mL for rubella virus, and lessthan 0.15 IU/mL for measles virus. Antibody levels indicatingan equivocal test result, defined as an antibody concentrationfor which it is unclear whether protection has been conferred,were defined as 50-100 IU/mL for varicella virus, 4-10 IU/mL for rubella virus, and 0.15-0.3 IU/mL for measles virus.The evaluation of anti–mumps virus antibody was conductedby means of a qualitative test.

The positive predictive value (PPV) of the self-report ques-tionnaire was defined as the probability, given an answer of“yes” to questions about the history of disease, vaccination,or both, that serological testing will confirm the respondent’simmunity to disease.11 Statistical evaluation of the results wasperformed by means of x2 analysis with the Yates correction.Statistical significance was defined as a P value of greater than.05 (determined using a 2-tailed test).

results

The mean age (�SD) of the 616 students who completedthe questionnaire was years. A total of 156 were22.9 � 5.6male (mean age [�SD], years), and 460 were23.1 � 5.1female (mean age [�SD], years). Most (523) of22.8 � 5.7the students were from northern Italy, 47 were from centralor southern Italy, and 46 were from other countries (21 were

from eastern Europe, 3 were from western Europe, 8 werefrom Africa, 6 were from Asia, and 8 were from Central orSouth America).

Sixteen subjects (2.6%) had markers of previous HBV in-fection but did not report a history of disease (Table 1); 12tested positive for anti-HBsAg and anti–HBV core antigenantibodies only, and 4 tested positive for HBsAg but not forHBeAg. A total of 501 subjects (81.3%) tested positive and99 (16.1%) tested negative for anti–HBsAg antibodies. Nu-merous subjects (86.9%) reported a history of hepatitis Bvaccination; of these, 91.8% tested positive and 6.7% testednegative for anti–HBsAg antibody; 1.5% had previous infec-tion. Finally, 10.2% of the subjects who reported no historyof hepatitis B vaccination tested positive for anti-HBsAg. Sub-jects younger than 25 years of age were significantly morelikely than subjects 25 years of age or older to report a historyof hepatitis B vaccination and test positive for anti-HBsAgantibodies ( ; data not shown). Self-reported historyP ! .001of hepatitis B vaccination had a PPV of 93.2% for a test resultpositive for anti-HBsAg antibodies (Table 2).

Most (93.7%) of the students tested positive for anti–var-icella virus antibody (Table 1), and few subjects (0.2%) hadequivocal test results. A history of varicella was reported by85.2% of the subjects, but 1.0% (6 subjects) reported havingreceived varicella vaccination. In addition, several students(65.1%) with no history of varicella tested positive for anti–varicella virus antibodies (Table 3). A large percentage ofstudents (98.3%) who reported a history of varicella testedpositive for anti–varicella virus antibodies (Table 3). Self-

This content downloaded from 194.29.185.222 on Fri, 16 May 2014 05:50:27 AMAll use subject to JSTOR Terms and Conditions

566 infection control and hospital epidemiology may 2007, vol. 28, no. 5

table 2. Positive predictive value (PPV) ofSelf-Reported History of Disease (HD) and/orVaccination Against Disease (HV) for Determin-ing Positive Results Serological Tests for Detec-tion of Viral Antibodies

Disease, HD and/or HV PPV, %

Hepatitis BHV only 93.2

VaricellaHD only 98.3

RubellaHD only 98.2HV only 98.1HD and HV 98.0

MumpsHD 92.0HV 73.2HD and HV 85.3

MeaslesHD 94.7HV 82.8HD and HV 86.3

note. PPV was defined as the probability, given a“yes” answer to the history of disease, vaccination, orboth, that the subject will be shown to be immune toa particular infectious disease by serological testing.11

Self-reported data were collected by a questionnairecompleted by 616 paramedical students who matric-ulated into Padua University Medical School (Padua,Italy) during 2003-2005.

reported history of varicella had a high PPV for a test resultpositive for anti–varicella virus antibodies (Table 2).

Serological testing revealed that the antibodies with thehighest prevalence were those against rubella virus (95.5% ofsubjects) (Table 1), with a significantly greater prevalenceamong females (97.2% vs 90.4%; ). Similar to resultsP ! .001of tests for detection of anti–varicella virus antibodies, fewtests (0.3%) for detection of anti–rubella virus antibody hadequivocal results. Few subjects (28.6%) reported a history ofrubella, but numerous subjects (62.7%) reported a history ofrubella vaccination; significantly more females than malesreported the latter (73.7% vs 30.1%; ). Self-reportsP ! .001of no history of rubella disease and no history of rubellavaccination were not predictive of a test result negative foranti–rubella virus antibodies; notwithstanding this, a signif-icantly greater percentage of students (84.6%) were immuneto rubella than were immune to varicella, mumps, and mea-sles ( ) (Table 3). PPVs for a test result positive forP ! .01anti–rubella virus antibodies were high for self-reported his-tory of disease (98.2%), vaccination (98.1%), or both (98.0%)(Table 2).

The prevalence of antibodies against mumps virus (79.9%)was significantly less than the prevalences of antibodiesagainst varicella virus ( ) and antibodies against ru-P ! .001bella virus ( ) (Table 1). Few subjects (45.1%) reportedP ! .001

a history of mumps, and self-reported history of mumpsvaccination was very low (32.0% of subjects). Self-reportedhistory of mumps had a PPV of 92.0% for testing positivefor anti–mumps virus antibodies (Table 3), but the prevalenceof these antibodies was high (66.9%) among subjects whodid not report a history of disease. On the contrary, only73.2% of subjects who reported history of vaccination testedpositive for anti–mumps virus antibodies, which is signifi-cantly lower than the percentage of positive test results amongsubjects who reported a history of disease only (92.%) andsubjects who reported a history of disease and vaccination(92.5%) ( ). In addition, a large percentage of testP ! .001results (7.6%) were equivocal; this finding was observed sig-nificantly more frequently among males than among females(14.1% vs 5.4%; ). The percentages of equivocal re-P ! .001sults and negative results of tests for detection of anti–mumpsvirus antibodies were significantly higher for subjects whoreported a history of mumps vaccination, compared withsubjects without a history of disease (equivocal results, 11.5%vs 4.2% [ ]; negative results, 15.3% vs 3.8% [ ])P ! .05 P ! .01(Table 3). Self-reported history of mumps had a PPV of 92.0%for testing positive for anti–mumps virus antibodies, but ahistory of vaccination had a PPV of only 73.2% (Table 2).

Finally, the prevalence of anti–measles virus antibodies waslow (83.1% of subjects); this finding was significantly lowerthan the prevalences of anti–varicella virus antibodies andanti–rubella virus antibodies ( ) (Table 1). Similar toP ! .001self-reported data for rubella, few subjects (31.5%) reporteda history of measles, but many (61.5%) reported a history ofmeasles vaccination. In contrast to findings for mumps, nosignificant difference in the frequency of test results negativefor antibodies against measles virus was found between sub-jects who reported a history of disease only and subjects whoreported a history of vaccination only (Table 3). However, ofthe 7.0% of test results that were equivocal for measles virus,a significantly higher percentage was observed for subjectswho reported a history of vaccination only than for thosewho reported a history of disease only (9.8% vs 0.7%;

). In addition, nearly all (95.3%) of the equivocal testP ! .001results were detected for subjects aged less than 25 years (datanot shown). A total of 94.7% of subjects with a reportedhistory of measles only tested positive for antibodies againstmeasles virus, compared with 82.8% who reported a vacci-nation history only ( ). Among subjects who testedP ! .001positive for antibodies against measles virus, the percentagewho had a history of disease and vaccination was less thanthe percentage who had a history of disease only (83.3% vs94.7%; ). On the contrary, several subjects (63.5%)P ! .05without a history of disease and/or vaccination tested positivefor antibodies against measles virus. Finally, self-reported his-tory of measles had a higher PPV (94.7%) than self-reportedhistory of vaccination only (82.8%) and self-reported historyof disease and vaccination (86.3%) for testing positive foranti–measles virus antibodies (Table 2).

This content downloaded from 194.29.185.222 on Fri, 16 May 2014 05:50:27 AMAll use subject to JSTOR Terms and Conditions

self-reported vaccination and disease history as a predictor of immunity 567

table 3. Results of Tests for Detection of Antibodies Against Viruses Causing4 Childhood Exanthematic Diseases, by Self-Reported History of Disease (HD)and/or Vaccination Against Disease (HV)

HD and/or HV,test result

No. (%) of subjects, by antibody(n p 616)

Anti–varicellavirus

Anti–rubellavirus

Anti–mumpsvirus

Anti–measlesvirus

No HD, no HVNegative 29 (33.7) 17 (14.5) 42 (23.3) 24 (28.2)Equivocal 1 (1.2) 1 (0.9) 18 (9.9) 7 (8.2)Positive 56 (65.1) 99 (84.6a) 121 (66.9) 54 (63.5)

Subtotal 86 117 181 85HD, no HV

Negative 9 (1.7) 2 (1.8) 9 (3.8) 7 (4.6)Equivocal 0 0 10 (4.2) 1 (0.7)Positive 515 (98.3) 111 (98.2) 219 (92.0) 144 (94.7)

Subtotal 524 113 238 152No HD, HV

Negative 0 5 (1.5) 24 (15.3b) 25 (7.4)Equivocal 0 1 (0.3) 18 (11.5c) 33 (9.8e)Positive 5 317 (98.1) 115 (73.2d) 279 (82.8f)

Subtotal 5 323 157 337HD, HV

Negative 0 2 (3.2) 2 (5.0) 5 (11.9)Equivocal 0 0 1 (2.5) 2 (4.8)Positive 1 61 (96.8) 37 (92.5) 35 (83.3g)

Subtotal 1 63 40 42

note. Self-reported data were collected by a questionnaire completed by 616 paramedicalstudents who matriculated into Padua University Medical School (Padua, Italy) during 2003-2005.a rubella vs varicella, mumps, and measles (positive results).P ! .001b vaccination vs disease history (negative results).P ! .05c vaccination vs disease history (equivocal results).P ! .01d vaccination vs disease history or both (positive results).P ! .001e vaccination vs disease history (equivocal results).P ! .001f vaccination vs disease history (positive results).P ! .001g disease and vaccination vs disease history (positive results).P ! .05

discussion

The aim of this research was to evaluate whether the PPV ofself-reported history of disease and/or vaccination for 5 trans-missible but vaccine-preventable diseases is high enough torender serological testing unnecessary. No students reporteda history of HBV infection, although some had immunolog-ical markers of previous infection. A high rate of compliancewith HBV vaccination recommendations was revealed byquestionnaire responses, particularly among subjects youngerthan 25 years (who were required to undergo vaccination),and a large percentage of respondents had an anti-HBsAgantibody level of at least 10 IU/L. Few vaccinated subjectshad negative results of tests for anti-HBV antibodies, butbecause previous data are not available, it is impossible todetermine whether they did not respond to the vaccine orwhether they no longer had circulating antibodies. Even ifgood (ie, 5-12–year) retention of immunologic memory inhealthy persons was demonstrated,12 receipt of a booster vac-

cination would be necessary to distinguish nonrespondersfrom those without antibodies. On the other hand, a studyof healthcare workers showed that no booster dose is requiredfor healthy adults for at least 10 years after receipt of primaryvaccination.13 Sixteen subjects reported no history of hepatitisB vaccination; 3 had markers of previous infection, and 4tested positive and 9 tested negative for anti-HBsAg anti-bodies. It is likely that some subjects gave dishonest responsesto the question about previous receipt of hepatitis B vaccine,because self-reported history of vaccination is highly asso-ciated with the detection of anti-HBsAg antibody. Finally,serological testing for HBV is more expensive than vacci-nating against hepatitis B (i33.60 vs i13.43), which suggeststhat mass vaccination is preferable to mass serological testing.

Self-reporting a history of varicella was highly predictiveof testing positive for anti–varicella virus antibodies (less than2% of subjects who reported a history of varicella had negativeor equivocal test results), but persons who had varicella when

This content downloaded from 194.29.185.222 on Fri, 16 May 2014 05:50:27 AMAll use subject to JSTOR Terms and Conditions

568 infection control and hospital epidemiology may 2007, vol. 28, no. 5

they were 6 months of age or younger may have a lower levelof anti–varicella virus antibodies.14 For this reason, a PPV of100% is difficult to achieve. The small percentage of subjectswho reported a history of varicella vaccination is probablyrelated to the fact that the vaccine has only been available inItaly since 2001. Six subjects claimed that they were vaccinatedagainst varicella, but the veracity of their responses is dubiousbecause they claimed to have been vaccinated before 2001.The cost of varicella vaccination is i35.70 per person, whichis higher than the cost of serological testing (i15.80 per per-son). For varicella, it appears that serological testing for an-tibodies against varicella virus is more cost-effective than vac-cinating against varicella.

The other childhood exanthematic diseases we analyzedrequire separate consideration. Since 1999, Italy has encour-aged trivalent vaccination with measles, mumps, and rubella(MMR) vaccine, and rubella vaccine is readily available toadolescent girls during secondary school. A large percentageof subjects who reported no history of rubella and/or rubellavaccination tested positive for antibodies against rubella virus.The discrepancy could be explained by the facts that exan-thema due to rubella may be not distinguishable from ex-anthema due to other causes and that the disease is frequentlysubclinical.15 Despite the large percentage of subjects immuneto rubella, the relatively low compliance with vaccinationrecommendations is the reason why rubella is still circulatingin Italy and congenital cases of rubella syndrome are stilloccurring.16

The prevalence of anti–measles virus antibodies was lowamong the surveyed students, many of whom had equivocalresults for tests for antibodies to this virus. Interestingly, thenumber of equivocal results was higher among subjects witha history of measles vaccination only, compared with thosewith a history of disease only, and equivocal results wereobserved almost exclusively among the younger students (ie,those less than 25 years of age). It is probable that the lowfrequency of equivocal results among subjects older than 25years is associated with immunity acquired through measlesacquisition. These conclusions are supported by the findingthat equivocal results were observed for a greater percentageof subjects who reported a history of vaccination only, com-pared with subjects who reported a history of disease only.This finding might be explained by incomplete vaccination(the vaccination strategy in Italy for mumps and measlesincludes 1 dose at 12-25 months of age and another dose at5-6 years of age); the CDC7 recommends that people withequivocal serological test results should be considered sus-ceptible to measles. The percentage of subjects who testedpositive for antibodies against measles virus was similaramong those who reported a history of disease and vacci-nation and those who reported a history of vaccination onlybut was less than the percentage among subjects who reporteda history of disease only. Excluding the possibility that vac-cination reduces the degree of immunity acquired by havingthe disease, this finding may be explained by the lack of

accuracy in questionnaire responses or the inability of thesubject to distinguish between other aspecific exanthemas andreactions to measles vaccine. For this reason, self-reportedhistory of disease only had a good PPV for a positive test foranti–measles virus antibodies.

The percentages of subjects who reported a history ofmumps, who reported a history of mumps vaccination, andwho tested positive for anti–mumps virus antibodies werelow. A large percentage of subjects had equivocal test resultsfor antibodies against mumps virus; the percentage wasgreater for subjects with a history of vaccination than forsubjects with a history of disease. The explanation of theseresults might be the same as that for the measles results.However, in contrast to our findings with respect to measles,the percentage of subjects who tested positive for anti–mumpsvirus antibodies was similar between subjects who reporteda history of disease and vaccination and subjects who reporteda history of disease only.

The cost of serological testing for anti–rubella virus anti-bodies, anti–mumps virus antibodies, and anti–measles virusantibodies is high (i56.90 per person), whereas MMR vaccineis inexpensive (i5.98 per person). However, if the decisionabout whether to perform serological testing is based on thePPV of self-reported history of disease, history of vaccination,or history of both, the choice is unclear, because the PPVsfor self-reported histories of disease, vaccination, or both arehigh for rubella but not for mumps and measles (this isparticularly true for self-reported vaccination history consid-ered alone).

Our findings regarding the PPVs for the childhood ex-anthematic diseases included in our study are similar to thosereported elsewhere,11,17-20 confirming that a significant per-centage of subjects who report a history of disease or vac-cination are not immune. It is difficult to believe that health-care workers receive the indirect benefit of herd immunity,because they may be exposed to a single infectious contact.Vaccination of all healthcare workers appears to be less ex-pensive than performance of serological tests (i33,947.76 vsi65,480.80), but less than half of healthcare workers withoutimmunity agree to be vaccinated against childhood exanthe-matic diseases.21 In addition, a mass-vaccination strategy thatinvolves administration of vaccines not mandated by lawmight come into conflict with the tenets of antivaccinationmovements or the beliefs of healthcare workers who objectto vaccination on the basis of conscientious or philosophicalgrounds, if the value of such a campaign is not defined.22

In conclusion, the results of this study confirm that a largepercentage of persons younger than 25 years of age have beenvaccinated against hepatitis B, with high immunization cov-erage among all survey respondents,23 and that the preva-lences of anti–varicella virus antibodies and anti–rubella virusantibodies are high.21 Moreover, they show that, for all dis-eases we studied except rubella, self-reported history of dis-ease has a higher PPV for immunity than does self-reportedvaccination history, equivocal results of serological tests for

This content downloaded from 194.29.185.222 on Fri, 16 May 2014 05:50:27 AMAll use subject to JSTOR Terms and Conditions

self-reported vaccination and disease history as a predictor of immunity 569

anti–mumps virus antibodies and anti–measles virus anti-bodies are common (probably because of incomplete vacci-nation regimens), the cost of serological testing appears tobe very high (approximately 2 times the cost of vaccination),and that possible strategies for achieving immunity amonghealthcare workers comprise vaccination of healthcare work-ers with no self-reported history of disease or vaccination,mass vaccination of all healthcare workers (to ensure coveragefor those who report a history of disease but test negative forantibodies), or serological testing of all healthcare workersprior to employment and subsequent vaccination of suscep-tible subjects. A mass-vaccination strategy is not practicablefor the reasons described above, and self-reported history ofdisease does not have a 100% PPV for immunity againstdisease. Despite the higher cost of serological testing, we agreewith others18 that the probability of not covering susceptiblesubjects is too high to exclude performance of testing todetermine immunity.

acknowledgments

Potential conflicts of interest. All authors report no conflicts of interest rel-evant to this article.

Address reprint requests to Andrea Trevisan, MD, Department of Envi-ronmental Medicine and Public Health, University of Padova, via Giustiniani2, Padova, 35128 Italy (andrea.trevisan@unipd.it).

references

1. Agerton TB, Mahoney FJ, Polish LB, Shapiro CN. Impact of the blood-borne pathogens standard on vaccination of healthcare workers withhepatitis B vaccine. Infect Control Hosp Epidemiol 1995; 16:287-291.

2. Davis RM, Orenstein WA, Frank JA Jr, Sacks JJ, Dales LG, Preblud SR,et al. Transmission of measles in medical setting: 1980 through 1984.JAMA 1986; 255:1295-1298.

3. Atkinson WL, Markowitz LE, Adams NC, Seastrom GR. Transmissionof measles in medical settings: United States, 1985-1989. Am J Med 1991;3(suppl 2):320S-324S.

4. Rivera ME, Mason WH, Ross LA, Wright HT Jr. Nosocomial measlesinfection in a pediatric hospital during a community-wide epidemic. JPediatr 1991; 119:183-186.

5. Centers for Disease Control and Prevention. Immunization of health-care workers: recommendations of the Advisory Committee on Im-munization Practices and the Hospital Infection Control Practices Ad-visory Committee. Morb Mortal Wkly Rep 1997; 46(RR-18):1-42.

6. Watson JC, Hadler SC, Dykewicz CA, Reef S, Phillips L. Measles, mumps,and rubella: vaccine use and strategies for elimination of measles, rubella,

and congenital rubella syndrome and control of mumps: recommen-dations of the Advisory Committee on Immunization Practices. MorbMortal Wkly Rep 1998; 47(RR-8):1-57.

7. Centers for Disease Control and Prevention. Prevention of varicella:update recommendations of the Advisory Committee on ImmunizationPractices. Morb Mortal Wkly Rep 1999; 48(RR-6):1-5.

8. Braunstein H, Thomas S, Ito R. Immunity to measles in a large popu-lation of varying age: significance with respect to vaccination. Am J DisChild 1990; 144:296-298.

9. Weber DJ, Weigle K, Rutala WA. Vaccines for healthcare workers. In:Plotkin SA, Orenstein WA, eds. Vaccines. Philadelphia: W. B. Saunders;1999:1107-1130.

10. Committee on Infectious Diseases. Varicella vaccine update. Pediatrics2000; 105:136-141.

11. Gallagher J, Quaid B, Cryan B. Susceptibility to varicella zoster virusinfection in health care workers. Occup Med (Lond) 1996; 46:289-292.

12. West DJ, Calandra GB. Vaccine induced immunologic memory for hep-atitis B surface antigen: implications for policy on booster vaccination.Vaccine 1996; 14:1019-1027.

13. Floreani A, Baldo V, Cristofoletti M, Renzulli G, Valeri A, Zanetti C, etal. Long-term persistence of anti-HBs after vaccination against HBV: an18 year experience in healthcare workers. Vaccine 2004; 22:607-610.

14. Baba K, Yabuuchi H, Takahashi M, Ogra PL. Immunologic and epide-miologic aspects of varicella infection acquired during infancy and earlychildhood. J Pediatr 1982; 100:881-885.

15. Gershon A. Rubella (German measles). In: Fauci AS, Braunwald E, Is-selbacher KJ, et al., eds. Harrison’s Principles of Internal Medicine. 14thed. New York: McGraw-Hill; 1998:1125-1127.

16. Ciofi degli Atti M, Filia A, Revello MG, Buffolano W, Salamaso S. Rubellacontrol in Italy. Euro Surveill 2004; 9:19-21.

17. Villasis-Keever MA, Pena LA, Miranda-Novales G, et al. Prevalence ofserological markers against measles, rubella, varicella, hepatitis B, hep-atitis C, and human immunodeficiency virus among medical residentsin Mexico. Prev Med 2001; 32:424-428.

18. Almuneef M, Memish ZA, Abbas ME, Balkhy HH. Screening healthcareworkers for varicella-zoster virus: can we trust the history? Infect ControlHosp Epidemiol 2004; 25:595-598.

19. MacMahon E, Brown L, Bexley S, Snashall DC, Patel D. Identificationof potential candidates for varicella vaccination by history: questionnaireand seroprevalence study. BMJ 2004; 7465:551-552.

20. De Juanes JR, Gil A, San-Martin M, Gonzalez A, Esteban J, Garcia deCodes A. Seroprevalence of varicella antibodies in healthcare workersand health sciences students: reliability of self-reported history of vari-cella. Vaccine 2005; 23:1434-1436.

21. Trevisan A, Morandin M, Frasson C, et al. Prevalence of childhoodexanthematic disease markers in paramedical students: need of vacci-nation. Vaccine 2006; 24:171-176.

22. Salmon DA, Teret SP, MacIntyre CR, Salisbury D, Burgess MA, HalseyNA. Compulsory vaccination and conscientious or philosophical ex-emptions: past, present, and future. Lancet 2006; 367:436-442.

23. Trevisan A, Borella-Venturini M, Di Marco L. Compliance with hepatitisB vaccine: a matter of force? Am J Infect Control 2006; 34:465-466.

This content downloaded from 194.29.185.222 on Fri, 16 May 2014 05:50:27 AMAll use subject to JSTOR Terms and Conditions