Vaccine 22 (2004) 329–334

A survey of attitudes towards paediatric vaccinationsamongst Canadian naturopathic students

Kumanan Wilsona,b,∗,1, Ed Millsc,2, Heather Boond,e,3, George Tomlinsona,b,d, Paul Ritvod

a Department of Medicine, University of Toronto, Toronto, Ont., Canada M5G 2C4b Department of Health Policy, Management and Evaluation, Faculty of Medicine, University of Toronto, Toronto, Ont., Canada M5G 2C4

c Department of Research, Canadian College of Naturopathic Medicine, Toronto, Ont., Canada M5G 2C4d Department of Public Health Sciences, Faculty of Medicine, University of Toronto, Toronto, Ont., Canada M5G 2C4

e Faculty of Pharmacy, University of Toronto, Toronto, Ont., Canada M5G 2C4

Received 9 May 2003; received in revised form 11 August 2003; accepted 12 August 2003

Abstract

Previous studies have suggested that providers of alternative medicine may harbour anti-vaccination attitudes and that these attitudesmay develop at an early stage in their careers. We further explored this question by conducting a survey to determine the attitudes of studentsof naturopathic medicine, a growing alternative medicine discipline, towards recommended paediatric vaccines. We sampled all 4 years ofstudents at the Canadian College of Naturopathic Medicine (CCNM) and obtained a response rate of 59.4% (312 of 525). We found thatonly 12.8% (40 of 312) of the respondents would advise full vaccination; however, 74.4% (232 of 312) of the respondents would advisepartial vaccination. Importantly, both willingness to advise full vaccination and trust in public health and conventional medicine decreasedin students in the later years of the programme. Our findings suggest that public health and conventional medical supporters of vaccinationneed to identify mechanisms for engaging in discussion with this population of complementary/alternative medical professionals at anearly stage in their careers.© 2003 Elsevier Ltd. All rights reserved.

Keywords: Immunisation; Naturopathic medicine; Attitudes

1. Introduction

Universal vaccination programmes have been centralcomponents of public health programmes around the world.Most developed nations have introduced universal child-hood vaccination for a variety of conditions. In Canada,all provinces have instituted public childhood vaccina-tion programmes for measles, mumps and rubella (MMR),Haemophilus influenzae type b (HIB), diphtheria, pertussisand tetanus (DPT) and polio[1]. In addition, several newvaccines are being considered for widespread implementa-tion [2–4].

Despite the documented successes of vaccinations, agrowing anti-vaccination movement appears to be emerg-ing. Factors contributing to this movement are thought to

∗ Corresponding author. Present address: ENG-254, Toronto GeneralHospital, University Health Network, 200 Elizabeth Street, Toronto, Ont.,Canada M5G 2C4. Tel.:+1-416-340-3662; fax:+1-416-595-5826.

E-mail address: kumanan.wilson@uhn.on.ca (K. Wilson).1 He is a Canadian Institutes of Health Research new investigator.2 He is an Essiac scholar.3 She is an Ontario Ministry of Health and Longterm Care career

scientist.

include the increased media attention given to the the-oretical risks associated with vaccination, the spread ofanti-vaccination information via the internet and the disap-pearance of vaccine-preventable diseases[5–7]. It has beensuggested that another contributor to the anti-vaccinationmovement may be the beliefs of some complementary andalternative medicine (CAM) providers[8].

Naturopathic medicine is a specific CAM disciplinethat is growing in popularity[9]. Naturopathy promotesa holistic approach to the treatment of medical condi-tions. It supports the use of “natural methods” to treat ill-nesses which make use of the body’s inherent “self-healingprocess”[10,11]. Patients may use naturopaths in combi-nation with their family physicians or as substitute familyphysicians[12,13]. As a consequence, naturopathic practi-tioners have the potential to influence behaviour on issuessuch as paediatric vaccination. It is, therefore, importantto understand naturopaths’ attitudes towards vaccination,particularly at an early stage in their career. To do so, weconducted a survey of students at the Canadian Collegeof Naturopathic Medicine (CCNM) to determine attitudestowards vaccination and to examine predictors of theseattitudes.

0264-410X/$ – see front matter © 2003 Elsevier Ltd. All rights reserved.doi:10.1016/j.vaccine.2003.08.014

330 K. Wilson et al. / Vaccine 22 (2004) 329–334

2. Methods

The Canadian College of Naturopathic Medicine is lo-cated in Toronto, Ont. and is the largest and only accreditedNaturopathic College in Canada. The Naturopathic pro-gramme consists of 4 years of in-school training at theend of which students receive a Doctor of Naturopathydegree. Students at this college are required to have a previ-ous bachelor’s degree with requisite sciences. The collegegraduates approximately 120 students per year.

In conjunction with CCNM, and with the approval of theirinstitutional ethics review board, we developed a survey todetermine the willingness of students currently enrolled atthe college to advise parents to vaccinate their children. Thissurvey is part of an ongoing collaborative exercise betweenCCNM and medical researchers to examine potential differ-ence in CAM and conventional practitioners’ attitudes to-wards vaccinations. Our primary objective was to determinethe willingness of students to recommend childhood vacci-nations, specified in the introduction to the survey as MMR,DPT, HIB and polio. We also sought to identify factors as-sociated with their willingness to recommend vaccinations,as well as to assess their perceptions of the risks of vaccina-tion. In order to accomplish these objectives, we developed a22-question survey, which we pre-piloted on five students todetermine if they adequately understood the questions. Theanonymous self-administered questionnaires were then dis-tributed following regularly scheduled classes to all 4 yearsof students in the CCNM programme. Students answered thequestionnaires while in class and returned them to the frontof the class where they were then collected by one of theinvestigators (Mills). Students had the option to not partici-pate if they wished. The survey was administered in March2001 to students enrolled in the academic year 2000/2001.

Of the 22 questions in the survey, five provided baselinedemographic information. We asked questions related to per-ceived risks and benefits of vaccines, willingness to adviseparents to vaccinate their children, reasons for not advisingvaccination, sources of information on vaccination and trustin sources of information.

2.1. Statistical analysis

The primary dependent variable assessed was willingnessto advise vaccination, which had response categories: (1) notwilling to advise any recommended vaccinations, (2) onlywilling to advise vaccination with some recommended vac-cines, and (3) willing to advise full vaccination. To makethe presentation of analysis easier, we collapsed this ordinaloutcome to the dichotomous outcome “willing to advise fullvaccination” versus“not willing to advise full vaccination”.We assessed simple relationships between this response andsix pre-specified dichotomised characteristics of students:(1) degree of belief that vaccines are beneficial (high andmoderate versus uncertain, low and none); (2) degree of trustin public health information (high and moderate versus low

and none); (3) year in the CCNM programme (1/2 years ver-sus 3/4 years); (4) knowledge of someone with an adversevaccine reaction (yes versus no); (5) degree of belief thatvaccines are risky (high and moderate versus uncertain, lowand none); (6) reliance upon only CAM providers for in-formation about vaccines (yes versus no). We computed thedifference in proportions (DP) for advising full vaccinationfor each of these variables and also carried out chi-squared(χ2) tests for the associated two-by-two tables. Using a mul-tivariable regression model, we assessed the effects on ad-vising full vaccination of these six variables, each adjustedfor the others. A proportional odds model was used to as-sess the relationship between the degree of trust in publichealth information (none, low, moderate/high) and year inthe programme. Comparing demographics for the entire stu-dent body (provided by the college) to those of our studyrespondents, we were able to infer the age and sex distri-butions for non-respondents and test for systematic age orsex differences between respondents and non-respondents.Analyses were carried out using S-Plus 6.0 (© 1998–2001,Insightful Corporation).

3. Results

3.1. Characteristics of respondents

A total of 357 out of 525 enrolled students (68% of studentbody) completed the survey. Of these, 45 did not provide ananswer to our primary question on willingness to vaccinateand were excluded from further analysis. We conducted themain body of analysis on the remaining 312 students (59.4%of original sample and 87% of respondents).

The students included in our final analysis were dis-tributed throughout the 4 years of the programme, with thehighest representation from second year and the lowest fromthe third and fourth years. The majority of the students weresingle females and they ranged in age from 20 to 55 (meanage: 27.4 years, S.D.: 4.5 years). A total of 11 (3.5%) stu-dents had children under the age of three (seeTable 1). Theindividuals who did not respond to our primary question(n = 45) were similar to those who did respond (n = 312)with respect to age, marital status, sex and graduating year.However, 8 of 45 (18%) of those who did not respond to ourprimary question had a child under the age of 3 years com-pared to the 3.5% who did respond, a large and statisticallysignificant difference (P < 0.0001). The sex ratio and meanage of the students included in our final analysis did notdiffer significantly from that of the student body as a whole.

3.2. Responses to vaccine attitude questions

3.2.1. Willingness to vaccinateIn response to the question “Based on your current knowl-

edge, would you advise your patients to have their childrenfully vaccinated?” 12.8% responded “No, I would advise

K. Wilson et al. / Vaccine 22 (2004) 329–334 331

Table 1Baseline characteristics

Variable Number (%)

Received questionnaire (n = 525) 357 (68.0)Answered primary question (n = 357) 312 (87.4)

Programme year (n = 312)First 78 (25.0)Second 115 (36.9)Third 57 (18.3)Fourth 62 (19.9)

Sex (n = 308)Males 61 (19.8)Female 247 (80.2)

Marital status (n = 308)Single 253 (81.4)Married 56 (18.0)Divorced/separated 2 (0.6)

Have children<3 years old (n = 311) 11 (3.5)

Age (n = 304) (years)20–24 61 (20.1)25–29 188 (61.8)30–34 30 (9.9)35–55 25 (8.2)

that they not receive any vaccinations”, 74.4% responded“No, I would only advise they vaccinated them with someof the recommended vaccines” and 12.8% responded “Yes,I would advise that they vaccinate them with all recom-mended vaccines”. Of the 87.2% that would not recommendfull vaccination, the most common reasons for this positionwere concerns about harm (74.3%) and about lack of benefit(33.5%) (seeTable 2).

3.2.2. Risks and benefits of vaccinesVaccines were believed to be highly or moderately bene-

ficial by 41.2% of the students and of minimal or no benefitby 35.0% of students. Vaccines were believed to be highlyor moderately risky by 67.3% and minimally risky or of norisk by 16.3% of students (seeTable 3).

When asked the question “How well understood arethe risks of vaccination?” 56.4% responded “minimally”,

Table 2Recommendation of paediatric vaccines

Variable Number (%)

Willingness to recommend vaccination (n = 312)No 40 (12.8)Partial 232 (74.4)Yes 40 (12.8)

Reasons for not recommending vaccinationa (n = 272)Concern about harm 202 (74.3)Concern about lack of benefit 91 (33.5)Philosophical objections 12 (4.4)Religious objections 2 (0.7)

a Allowed to mention more than one.

Table 3Perception of benefits and risks of vaccination

Perception Number (%)

Vaccine benefits (n = 311)Highly beneficial 34 (10.9)Moderately beneficial 94 (30.2)Minimally beneficial 95 (30.5)No benefit 14 (4.5)Uncertain 74 (23.8)

Vaccine risks (n = 311)Highly risky 33 (10.6)Moderately risky 177 (56.9)Minimally risky 49 (15.8)No risk 2 (0.6)Uncertain 50 (16.1)

32.7% responded “moderately”. Only 2.9% responded “wellunderstood” and 8% responded that they did not know. Al-most half (48.7%) of the students reported that they wereaware of someone who had a negative or harmful reactionto a vaccination. The vaccines most commonly reported tohave produced these reactions were MMR (22.6% of thosewitnessing adverse reactions), the flu vaccine (14.0%) andDPT (10.0%) (this was an open-ended question).

When asked which vaccine they considered to be the leastsafe, the majority (65.4%) did not know. MMR was identi-fied by 7.8%, DPT by 4.7%, Hib by 4.4% and polio by 4.7%.Only 2.0% believed all vaccines were safe and 10.8% be-lieved all were unsafe. When asked which vaccine they con-sidered to be the most beneficial, again the majority (55.2%)did not know. DPT was identified by 11.2%, 8.0% chose po-lio, 6.3% chose MMR and 2.1% chose Hib. Only 7.7% saidall were beneficial and 9.4% said none were beneficial.

3.2.3. Sources of information and trust in sourcesWhen asked where they obtained information on vaccina-

tion issues, 52.9% stated CAM providers, 19.9% stated text-books and journals, 19.2% stated allopathic providers andpublic health officials and 9.3% stated the internet or me-dia. Students expressed more trust in vaccination informa-tion provided by CAM providers as opposed to informationprovided by allopathic providers or public health informa-tion when it came to vaccination issues (Table 4). Only a few(7.2%) students had either low or no trust in advice providedby CAM practitioners. In contrast, 60.5% had low/no trustin public health information and 66.2% had low/no trust inadvice from allopathic providers (seeTable 4).

Table 4Trust in sources of information on vaccination

Source of information Level of trust number (% within row)

None Low Moderate High

CAM 1 (0.3) 21 (6.9) 223 (72.9) 61 (19.9)Public Health 27 (8.7) 160 (51.8) 116 (37.5) 6 (1.9)Allopaths 38 (12.3) 166 (53.9) 97 (31.5) 7 (2.3)

332 K. Wilson et al. / Vaccine 22 (2004) 329–334

Table 5Factors predicting willingness to advise full vaccination (bivariate analysis)

Survey response Percentage willing toadvise full vaccination

Difference in proportions(95% confidence interval)

P-value

Vaccines are of high/moderate benefit 28.9 27.3 (19.2–35.3) <0.0001Vaccines are of no, minimal or uncertain benefit 1.6

High/moderate trust in public health information 27.1 23.3 (15.0–31.6) <0.0001Low/no trust in public health information 3.7

Vaccines are of no, minimal or uncertain risk 26.7 20.5 (11.3–30.0) <0.0001Vaccines are of high/moderate risk 6.2

No knowledge of individual with adverse reaction to vaccination 21.5 18.2 (11.1–25.2) <0.0001Knowledge of individual with adverse reaction to vaccination 3.3

First/second year students 19.7 18.0 (11.9–24.1) <0.0001Third/fourth year students 1.7

CAM is not only source of vaccination information 18.4 12.6 (5.6–19.5) 0.002CAM is only source of vaccination information 5.8

Table 6Raw and adjusted odds ratios of variables predicting willingness to advise vaccinations

Variablea Unadjusted analysis Adjusted analysis

OR OR 95% confidence interval

High or moderate belief that vaccines are beneficial 24.4 16.4 5.15–73.6High or moderate trust in public health information 9.5 3.72 1.42–10.7

Progression through programme (3/4 years vs. 1/2 years) 0.07 0.13 0.02–0.52Knowledge of someone with adverse vaccine reaction 0.13 0.26 0.08–0.76Belief that vaccines are highly or moderately risky 0.18 0.30 0.11–0.74Reliance upon only CAM providers for information 0.28 0.59 0.21–1.63

a Each odds ratio is for the comparison of subjects with the characteristic in this column to subjects without this characteristic, unless otherwisespecified.

3.2.4. Predictors of decision to advise vaccinationOur bivariate analyses identified that the following factors

were associated with a statistically significant difference inthe proportions recommending full vaccination: perception

Fig. 1. Trust in public health vs. year in programme. The dots showobserved percentages and the lines show 95% confidence intervals.

of benefit or risk of vaccines, trust in public health, yearin programme, knowledge of an individual with an adversevaccine reaction and reliance upon CAM information onvaccines (seeTable 5). We also observed that the proportionof students who had low or no trust in public health infor-mation declined by year in programme (P < 0.001) (Fig. 1).

The result of the multivariable analyses based on thesevariables was that all variables, except reliance upon CAMfor vaccine information, remained statistically significant in-dependent predictors of the decision to advise vaccination.Table 6 lists both unadjusted (bivariate) and the adjustedodds ratios associated with these variables. An odds ratiolarger than one for a variable indicates that a student withthe characteristic described has an increased probability ofrecommending full vaccination, compared to a student with-out that characteristic.

4. Discussion

Several messages emerge from our study of the attitudestowards vaccination of students at a major Canadian natur-opathic college. Of most concern to public health officialsis that only a minority of students would advise parentsto have their children receive all recommended paediatric

K. Wilson et al. / Vaccine 22 (2004) 329–334 333

vaccinations. The decision not to recommend vaccinationwas due to a combination of concerns about the lack ofbenefit of these vaccines and their potential risk. Our studyalso found that “anti-vaccination” attitudes were presentamongst students in their first year at the NaturopathicCollege and increased in students who had been in theprogramme for a longer duration. This trend appeared tobe partially mediated by a progressive decrease in trust inpublic health sources of information on vaccination. Wealso identified that knowledge of an individual who has hada vaccination reaction was independently associated with anegative attitude towards vaccination.

On a closer examination of the data, however, it appearsthat students have a considerable level of uncertainty re-garding the risks and benefits of vaccination. The majorityof students stated they would recommend vaccination withsome of the recommended vaccinations. Many students wereuncertain as to the level of risk and benefit associated withvaccines. We also found that students’ negative attitudestowards vaccination did not appear to be specific to any par-ticular vaccine, but rather to vaccines in general as demon-strated by the high percentage of students who did not knowwhich vaccine was the most beneficial or the most risky.

The results of our survey are consistent with those of otherstudies. A study of practising naturopathic doctors in Mas-sachusetts, USA found that only 3 of 15 (20%) naturopathswould actively recommend vaccinations, although only 1(7%) openly opposed vaccinations[14]. Another study iden-tified a substantial level of heterogeneity in attitudes towardsvaccination amongst naturopaths with many discouragingtheir use[15]. Studies of other CAM disciplines also areconsistent with our findings. Most notably, a survey of 467students from the Canadian Memorial Chiropractic Collegefound that while 53.5% of students were in favour of vac-cination, the remainder of students did not agree (14.1%)with vaccination or were unsure (32.3%). This study alsoidentified an upward trend in anti-vaccine beliefs as studentsprogressed through the chiropractic programme[16].

A possible limitation of our study is the potential forboth non-responder bias and item non-response bias. Whilewe found that those who responded to the survey weresimilar in age and sex to the average student this does notnecessarily imply that they shared similar attitudes towardsvaccination. In examining the issue of item non-response,we found it interesting that those who chose not to answerthe question of whether they would recommend vaccina-tions were more likely to have children under the age of 3years. If we assumed that all of these individuals had sup-ported full vaccination, the percentage of those supportingfull vaccination would increase to 24%, still only a minority.Another important limitation of our study is that it cannotdetermine the directionality of the associations we observed.Specifically, it cannot establish whether individuals who areanti-vaccination are drawn towards naturopathic medicineor whether training in naturopathic medicine contributes tothe development of anti-vaccination attitudes.

We also have to be cautious about interpreting conclu-sions about anti-vaccination attitudes increasing as students’progress through the programme because this inference isbased on a comparison of different populations of studentsin different years rather than observing one population overseveral years. A hypothesis that needs to be further ex-amined is that individuals who have belief systems moreconsistent with choosing naturopathy as a career are morelikely to be sceptical of vaccinations. These individuals’ at-titudes may then be reinforced by their continued exposureto CAM. However, CCNM states that it does not activelyteach about the risks of vaccinations. Students are also toldnot to make recommendations against childhood vaccina-tions. Therefore, a possible explanation for our observationsis that students’ anti-vaccination attitudes are intensified andvalidated by the presence of other students with similar be-liefs. More in depth qualitative research is required to betterestablish why these anti-vaccination beliefs develop.

Our survey, and the chiropractic student survey, also sug-gest that public health officials need to identify mechanismsto counteract the apparent progressive decrease in trust ofconventional sources of vaccination information as studentsprogress through these programmes. This would require de-termining how to effectively engage CAM providers, par-ticularly early in their training. A possible strategy wouldbe to cautiously acknowledge some of their concerns, forexample that vaccines are not 100% safe and that they arenot 100% effective[17]. At the same time, public health of-ficials need to provide a clear message that the benefits ofvaccination are large compared to the risks. These messagesneed to be presented in a manner that CAM providers will bemost receptive to and that respects their concerns. The em-phasis on individualising therapy in many CAM disciplinesmay suggest that case examples of individuals who havedeveloped potentially vaccine-preventable conditions couldbe effective in persuading CAM providers of the benefits ofvaccination. The potential effectiveness of such “anecdotal”information is supported by our survey finding of a nega-tive association between knowledge of a patient with an ad-verse vaccine reaction and willingness to advise vaccination.The effectiveness of different forms of evidence in chang-ing attitudes towards vaccination needs to be tested in futurestudies.

The potential receptivity of the CAM practitioner com-munity to be engaged in debate with the conventionalmedical community on the issue of vaccination is demon-strated by the willingness of CCNM and the CanadianMemorial Chiropractic College allowing their students’ at-titudes towards vaccination to be examined. Additionally,the apparent uncertainty towards vaccination identified byour study suggests that the right strategy may help to alle-viate concerns about vaccination. This uncertainty is alsoreflected in the cautiously supportive official statement fromthe Canadian Naturopathic Association regarding vaccina-tions. The association states that “immunisations may beeffective for controlling the incidence of specific contagious

334 K. Wilson et al. / Vaccine 22 (2004) 329–334

diseases” and that “immunisations can cause serious ad-verse reactions, possibly even fatal, in a small minority ofchildren”. The Association also states that parents shouldbe well informed of the benefits and risks of vaccinationand that there are no natural “substitutes” for immunisation[18].

5. Conclusion

Public health officials need to ensure that current high lev-els of vaccination coverage are maintained. Concerns aboutthe safety and benefit of vaccination amongst naturopathicproviders have the potential to erode parents’ confidencein vaccines. Finding effective mechanisms to communicatethe benefits of vaccination to naturopathic providers dur-ing their training is an important first step to prevent thisfrom occurring. Naturopathic providers who support vacci-nation should also be aware of these results and considerintroducing changes in curriculum to inform students aboutthe favourable risk/benefit profile of many paediatric vac-cines. We strongly recommend that members of the publichealth community, conventional medicine and naturopathicmedicine begin a dialogue on these issues.

Acknowledgements

This study was funded by a Canadian Institutes of Healthgrant.

References

[1] Current Immunisation Programs in Canada. Canadian nationalreport on immunisation, 1996. Canada communicable disease report,Supplement vol. 23S4. Laboratory Centre for Disease Control, HealthCanada; May 1997 [Chapter 10].

[2] Pinker S. Quebec’s $100-million campaign targets meningococcaldisease (news). CMAJ 2001;165(11):1520.

[3] Province-wide meningococcal immunisation program gets underway.Government of Alberta news release (http://www.gov.ab.ca/acn/200104/10533.html, accessed 15 January 2002).

[4] Scheifele D, Halperin S, Pelletier L, Talbot J. Invasive pneumococcalinfections in Canadian children, 1991–1998: implications for newvaccination strategies. Canadian Paediatric Society/Laboratory Centrefor Disease Control Immunisation Monitoring Program, Active(IMPACT). Clin Infect Dis 2000;31:58–64.

[5] Cookson C. Benefit and risk of vaccination as seen by the generalpublic and the media. Vaccine 2002;20:S85–8.

[6] Wolfe RM, Sharp LK, Lipsky MS. Content and design attributes ofanti-vaccination websites. JAMA 2002;287:3245–8.

[7] Gangarosa EJ, Galazka AM, Wolfe CR, et al. Impact of anti-vaccine movements on pertussis control: the untold story. Lancet1998;351:356–61.

[8] Ernst E. Rise in popularity of complementary and alternativemedicine: reasons and consequences for vaccination. Vaccine2002;20:S90–3.

[9] Cooper RA, Laud P, Dietrich CL. Current and projected workforceof nonphysician clinicians. JAMA 1998;280:788–94.

[10] What is naturopathic medicine? Canadian Naturopathic Medicine(http://www.naturopathicassoc.ca/qa1.html, accessed 23 July 2002).

[11] Definition of naturopathic medicine. The American Associationof Naturopathic Physicians (http://www.naturopathic.org/about/definitions.htm, accessed 23 July 2002).

[12] Featherstone C, Godden D, Gault C, Emslie M, Took-Zozaya M.Prevalence study of concurrent use of complementary and alternativemedicine in patients attending primary care services in Scotland. AmJ Public Health 2003;93:1080–2.

[13] Spigelblatt L, Laine-Ammarra G, Pless IB, Guyver A. The use ofalternative medicine by children. Pediatrics 1994;94:811–4.

[14] Lee ACC, Kemper KJ. Homeopathy and naturopathy. Arch PediatrAdolesc Med 2000;154:75–80.

[15] Halper J, Berger LR. Naturopaths and childhood immunisations:heterodoxy among the orthodox. Pediatrics 1981;68:407–10.

[16] Busse JW, Kulkarni AV, Campbell JB, Injeyan HS. Attitudes towardvaccination: a survey of Canadian chiropractic students. CMAJ2002;166:1531–4.

[17] Plotkin SA. Lessons learned concerning vaccine safety. Vaccine2002;20:S16–9.

[18] Childhood vaccinations. Position Paper ratified by CNA/ACN Boardof Directors, 29 March 2000.