Papers

Reasons for non-uptake of measles, mumps, and rubella catch up immunisation in a measles epidemic and side effects of the vaccine

BMJ 1995; 310 doi: http://dx.doi.org/10.1136/bmj.310.6995.1629 (Published 24 June 1995) Cite this as: BMJ 1995;310:1629
  1. Richard J Roberts,
  2. Quentin D Sandifer,
  3. Merion R Evans,
  4. Maria Z Nolan-Farrell,
  5. Paul M Davis
  • Accepted 13 April 1995

Abstract

Objective —To investigate the reasons for poor uptake of immunisation (non-immunisation) and the possible side effects of measles, mumps, and rubella vaccine in a catch up immunisation campaign during a community outbreak of measles.

Design —Descriptive study of reasons for non-immunisation and retrospective cohort study of side effects of the vaccine.

Setting —Secondary schools in South Glamorgan.

Subjects —Random cluster sample of the parents of 500 children targeted but not immunised and a randomised sample of 2866 of the children targeted.

Main outcome measures —Reasons for non-immunisation; symptoms among immunised and non-immunised children.

Results —Immunisation coverage of the campaign was only 43.4% (7633/17,595). The practicalproblems experienced included non-return of consent forms (6698/17,595), refusal of immunisation (2061/10,897 forms returned), and absence from school on day of immunisation (1203/8836 children with consent for immunisation). The most common reasons cited for non-immunisation were previous measles infection (145/232),previous immunisation against measles (78/232), and concern about side effects (55/232). Symptoms were equally common among immunised and non-immunised subjects. However, significantly more immunised boys than non-immunised boys reported fever (relative risk 2.31 (95% confidence interval 1.36 to 3.93)), rash (2.00 (1.10 to 3.64), joint symptoms (1.58; 1.05 to 2.38), and headache (1.31 (1.04 to 1.65)).

Conclusions —Many of the objections raised by parents could be overcome by emphasising that primary immunisation does not necessarily confer immunity and that diagnosis of measles is unreliable. Measles, mumps, and rubella vaccine is safe in children aged 11-15.

  • Parents frequently object to immunisations for their children on various grounds, including previous immunity and concern about adverse effects

  • Previous immunisation or clinical measles was found to be a frequent reason for non-immunisation in a mass campaign

  • Advice to parents should emphasise that primary immunisation against measles, mumps, and rubella may fail to confer immunity and that a clinical diagnosis of measles is unreliable

  • The incidence of adverse effects of measles, mumps, and rubella vaccine in the 11-15 year age group in the United Kingdom is low

Introduction

Measles vaccine became part of the childhood immunisation programme in the United Kingdom in 1968; it was replaced in 1988 by measles, mumps, and rubella vaccine given as a single dose to children at the age of 12-15 months. Although notifications of measles reached an all time low in the United Kingdom in 1993, serological surveillance shows that the proportion of children over 10 lacking measles antibody is rising, along with the proportion of cases of measles occurring in older children.[1][2][3][4][5] Outbreaks in secondary schools in the United Kingdom have mainly affected non-immunised pupils, but those in schools and colleges in the United States, where uptake of immunisation is high, have largely affected immunised subjects.[6][7][8][9][10][11]

We studied the reasons for non-immunisation and the side effects from the vaccine during a measles, mumps, and rubella catch up immunisation campaign mounted in response to an outbreak of measles.

Subjects and methods

An outbreak of measles affecting 450 people occurred in South Glamorgan from December 1993 to June 1994. All children in the first five years of secondary school (mostly aged 11-15) who had no record on the child health computer of having been previously immunised against measles were targeted for immunisation with measles, mumps, and rubella vaccine during February to April 1994. Information on this catch up immunisation campaign was sent in advance to all concerned, and the campaign was widely reported in the local media. During the campaign almost 26 000 computerised immunisation records were checked, 17 595 consent forms dispatched, and 7633 (43.4%) children from 46 schools immunised (Fig 1).

Fig 1
Fig 1

Immunisation coverage of pupils in first five years of secondary school in measles, mumps, and rubella catch up campaign in South Glamorgan, 1994

REASONS FOR NON-IMMUNISATION

After the campaign all children in the target group who had not been immunised were identified from the enrolment list of every school. From these a two stage random sample of 500 pupils was chosen by first selecting 10 schools, from each of which 50 non-immunised pupils were selected.

A one page questionnaire with a covering letter and a reply paid envelope were posted to the pupils' parents within a month of the end of the immunisation campaign. A second package was posted one month later to those who did not respond. The questionnaire asked whether parents had received and returned the consent form and whether consent had been given (“Did you agree for your child to receive MMR vaccine in school?”). Parents who had not given their consent were asked to indicate the reasons for their decision.

SIDE EFFECTS ASSOCIATED WITH THE VACCINE

A retrospective cohort study was conducted among all pupils targeted by the immunisation campaign. A two stage random sample of 2866 pupils was obtained. Fifteen schools were selected; 100 children who had been immunised in the campaign and 100 who had not were chosen from each of the 13 large schools, while all pupils were included from the two remaining, smaller schools. The sample, 13% of the target population, was large enough to detect associations of interest with a power of 90%, although it was not sufficient to examine the risk of rare events such as postvaccine encephalitis. Data were collected from four weeks after the start of the campaign to six weeks after the programme's end.

A one page questionnaire with a covering letter and reply paid envelope were posted to all parents. Those who did not respond were sent another package after two weeks. The questionnaire asked about the occurrence of symptoms commonly associated with measles, mumps, and rubella vaccine over the previous four weeks and also about previous immunisation against measles or rubella.

STATISTICAL ANALYSIS

Analysis was carried out using EPI INFO.[12] The significance of any differences between immunised and non-immunised groups was tested using a κ2 test with Yates's correction, and relative risks were calculated with Greenland Robins 95% confidence intervals.

Results

REASONS FOR NON-IMMUNISATION

A total of 307 parents (61%) returned completed questionnaires. Of these, 160 reported having returned the consent form, 121 had not returned it, 22 had not received it, and four gave no answer (fig 2).

Fig 2
Fig 2

Receipt and return of consent forms by parents of random sample of children who were not immunised in catch up campaign

Two hundred and thirty two parents refused their consent for immunisation, 42 reported having given their consent, and 33 did not answer the question. Of the 232 parents who refused consent, 120 returned the consent form, 111 indicated refusal of consent by not returning it, and one did not answer the question. Those who returned the form gave the same reasons for refusing their consent for immunisation as those who did not return it.

Of the 232 who refused to give their consent (table 1), 195 gave either previous measles infection or previous immunisation against measles or measles, mumps, and rubella, or both, as the reason. The 37 others gave various reasons, which are listed in table 1. Most parents (128) gave a single reason for refusal, 69 gave two reasons, and 35 three or more reasons. Figure 3 shows the relation between certain reasons for refusal.

Fig 3
Fig 3

Relation between three reasons given by 232 parents for having refused consent for measles, mumps, and rubella immunisation. GP = General practitioner; MMR = measles, mumps, and rubella immunisation

Table I

Reasons given by 232 parents for refusing consent to catch up immunisation*

View this table:

The cases of the 42 children whose parents agreed to measles, mumps, and rubella immunisation but who were not immunised were investigated. Of 30 records traced, 25 showed that pupils had failed to return their consent form to school. Overall, 22 out of 307 (7.7%) parents did not receive a consent form in the campaign (loss probably occurring while the form was with the pupil), 25 out of 307 (8%) consented to immunisation but the pupil did not return the consent form to school, and 23 out of 232 (10%) parents gave the child not wanting an injection as a reason for refusing consent.

SIDE EFFECTS ASSOCIATED WITH THE VACCINE

Completed questionnaires were returned for 2170 children (75.7%). The mean age of subjects was 13.5 years; 1200 were boys and 940 girls (the sex was unknown in 30 subjects). Of the 1081 respondents whose children were immunised during the campaign, 932 (86.2%) answered the question about previous measles immunisation, 475 of them reporting previous immunisation. Immunisation during the campaign was significantly more likely if parents reported no previous measles immunisation (72.5% v 35.3% if previously immunised, relative risk 1.49 (95% confidence interval 1.45 to 1.53)).

The most frequently reported symptoms in both immunised and non-immunised groups were headache and sore throat (25.2% and 22.5% respectively) (table II). Immunised subjects reported significantly less cough (P=0.04). Redness or swelling at the injection site lasting more than one day was reported by 56 children (5.2%). Four (<1%) immunised boys reported testicular swelling or pain.

Table II

Frequency of symptoms among immunised and non-immunised children during the six weeks after measles, mumps, and rubella immunisation

View this table:

Analysis by sex (table III) showed no differences in immunised and non-immunised girls. Immunised boys, however, reported significantly more fever (relative risk 2.31 (1.36 to 3.93)), rash (relative risk 2.00 (1.10 to 3.64)), joint symptoms (relative risk = 1.58 (1.05 to 2.38)), and headache (relative risk 1.31 (1.04 to 1.65)) than non-immunised boys.

Table III

Frequency of symptoms by sex among immunised and non-immunised children after measles, mumps, and rubella immunisation

View this table:

Analysis by sex (table III) showed no differences in immunised and non-immunised girls. Immunised boys, however, reported significantly more fever (relative risk 2.31 (1.36 to 3.93)), rash (relative risk 2.00 (1.10 to 3.64)), joint symptoms (relative risk = 1.58 (1.05 to 2.38)), and headache (relative risk 1.31 (1.04 to 1.65)) than non-immunised boys.

Those who were immunised were significantly less likely to visit an outpatient department (four compared with 14 visits, P = 0.03). The two groups did not differ significantly in terms of the number of consultations with a general practitioner or admissions to hospital.

Discussion

REASONS FOR NON-IMMUNISATION

Uptake in this school catch up immunisation campaign was poor despite extensive publicity. The main reasons for non-immunisation were previous infection with or immunisation against measles. Measles was not considered to be a serious illness by 6% of parents. Other studies have shown that older children are perceived to be less vulnerable to infections than infants.[13] Although lack of support from doctors was the main reason for poor uptake in other studies, under 10% of our sample reported that their general practitioner had said that measles, mumps, and rubella immunisation was not needed. Such advice may have been correct for some of the pupils.” False contra-indications were given as a reason by only 7% of those who refused consent, which is lower than elsewhere.[13] [14] [16] Important factors in other studies include lack of literacy in English among parents and the mobility of families.[17] The non-immunised group in this campaign probably included most of the children who did not receive their full primary imunisations.[18] Failure to immunise these children is a particular problem of mass campaigns.

SIDE EFFECTS ASSOCIATED WITH THE VACCINE

To our knowledge, the side effects of measles, mumps, and rubella vaccine have not been studied in the United Kingdom in children aged 11-15. We found no significant overall difference in reported symptoms between the immunised and non-immunised groups, which is consistent with findings elsewhere.[19][20][21] The other reports, however, are based on populations whose prevalence of immunity is likely to have been different from ours.

A double blind crossover trial in twins found that only 6% of those immunised developed any adverse events.[22] Fever was the most common reaction, usually developing on days 7 to 12, with a peak on days 9 and 10.[22] The pilot study for measles, mumps, and rubella immunisation in the United Kingdom found that fever, rash, and poor appetite were the most common symptoms in children aged 1-2 years and that side effects were fewer in older children (aged 4-5 years).[23] Our finding of significant differences in symptoms between immunised and non-immunised boys was probably because most boys had not previously received rubella vaccine, whereas most girls (89%) had. A recognised association exists between rubella immunisation and joint symptoms.[24] [25] Although some of these associations may be due to chance, lack of immunity to rubella among boys is a plausible explanation for the observed pattern. We did not use a correction method for the large number of associations studied since this would have resulted in a significant loss of power.

CONCLUSIONS AND RECOMMENDATIONS

Despite a local epidemic and extensive planning and intense publicity, our campaign achieved poor coverage. The main reasons for refusal of immunisation were previous measles infection, previous measles immunisation, concerns about the side effects of the vaccine, and lack of pupil compliance.

Our findings confirm that the incidence of side effects from measles, mumps, and rubella vaccine is low in children aged 11-15, irrespective of whether they have been immunised before. Many of the objections raised by parents could be overcome by providing clear and consistent professional advice and by emphasising that primary immunisation with measles vaccine or measles, mumps, and rubella vaccine does not confer immunity on all recipients. Diagnosis of measles is unreliable, and doctors have a responsibility for improving diagnostic accuracy.[26] Furthermore, achieving high coverage also requires strenuous efforts in following up those who fail to respond to offers of immunisation; such efforts will also need to include being flexible about when immunisation can be performed.

Our campaign shows many of the problems likely to be encountered by national immunisation campaigns based on schools. The lessons learnt apply to similar campaigns that may be contemplated by other developed countries in their drive to eliminate measles by 2000.

We thank our colleagues in the child health department of Cardiff Community Health Care, especially Mrs Margaret Morgan, for their help in obtaining data, and Professor Stephen Palmer and Dr Roland Salmon for their support and advice. This investigation arose from the routine work of the department of public health medicine of South Glamorgan Health Authority and the Public Health Laboratory Service Communicable Disease Surveillance Centre (Welsh Unit).

References

  1. 1.
  2. 2.
  3. 3.
  4. 4.
  5. 5.
  6. 6.
  7. 7.
  8. 8.
  9. 9.
  10. 10.
  11. 11.
  12. 12.
  13. 13.
  14. 14.
  15. 15.
  16. 16.
  17. 17.
  18. 18.
  19. 19.
  20. 20.
  21. 21.
  22. 22.
  23. 23.
  24. 24.
  25. 25.
  26. 26.
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