Human papillomavirus (HPV) vaccination coverage in young

Vaccine 32 (2014) 592–597
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Vaccine
journal homepage: www.elsevier.com/locate/vaccine
Human papillomavirus (HPV) vaccination coverage in young
Australian women is higher than previously estimated: Independent
estimates from a nationally representative mobile phone survey
Julia M.L. Brotherton a,b,c,∗ , Bette Liu d , Basil Donovan d,e , John M. Kaldor d , Marion Saville a
a
National HPV Vaccination Program Register, VCS Inc., PO Box 310, East Melbourne 8002, Victoria, Australia
Discipline of Paediatrics and Child Health, University of Sydney, Locked Bag 4001, Westmead 2145, New South Wales, Australia
c
Melbourne School of Population and Global Health, 207 Bouverie Street, The University of Melbourne, Parkville, Victoria 2010, Australia
d
The Kirby Institute, University of New South Wales, Sydney 2052, New South Wales, Australia
e
Sydney Sexual Health Centre, Sydney Hospital, PO Box 1614, Sydney 2001, New South Wales, Australia
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Background: Accurate estimates of coverage are essential for estimating the population effectiveness
of human papillomavirus (HPV) vaccination. Australia has a purpose built National HPV Vaccination
Program Register for monitoring coverage, however notiﬁcation of doses administered to young women
in the community during the national catch-up program (2007–2009) was not compulsory. In 2011, we
undertook a population-based mobile phone survey of young women to independently estimate HPV
vaccination coverage.
Methods: Randomly generated mobile phone numbers were dialed to recruit women aged 22–30 (age
eligible for HPV vaccination) to complete a computer assisted telephone interview. Consent was sought to
validate self reported HPV vaccination status against the national register. Coverage rates were calculated
based on self report and weighted to the age and state of residence structure of the Australian female
population. These were compared with coverage estimates from the register using Australian Bureau of
Statistics estimated resident populations as the denominator.
Results: Among the 1379 participants, the national estimate for self reported HPV vaccination coverage
for doses 1/2/3, respectively, weighted for age and state of residence, was 64/59/53%. This compares
with coverage of 55/45/32% and 49/40/28% based on register records, using 2007 and 2011 population
data as the denominators respectively. Some signiﬁcant differences in coverage between the states were
identiﬁed. 20% (223) of women returned a consent form allowing validation of doses against the register
and provider records: among these women 85.6% (538) of self reported doses were conﬁrmed.
Conclusions: We conﬁrmed that coverage rates for young women vaccinated in the community (at age
18–26 years) are underestimated by the national register and that under-notiﬁcation is greater for second
and third doses. Using 2011 population estimates, rather than estimates contemporaneous with the
program rollout, reduces register-based coverage estimates further because of large population increases
due to immigration since the program.
© 2013 Elsevier Ltd. All rights reserved.
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Article history:
Received 30 July 2013
Received in revised form
11 November 2013
Accepted 21 November 2013
Available online 5 December 2013
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Keywords:
Human papillomavirus (HPV)
Vaccination coverage
Australia
1. Introduction
In mid-2007 the Australian government introduced a National
Human Papillomavirus (HPV) Vaccination Program. The prophylactic quadrivalent vaccine used prevents infection with HPV types
∗ Corresponding author at: National HPV Vaccination Program Register, VCS Inc.,
PO Box 310, East Melbourne 8002, Victoria, Australia. Tel.: +61 3 9250 0377;
fax: +61 3 8417 6835.
E-mail addresses: [email protected] (J.M.L. Brotherton),
[email protected] (B. Liu), [email protected] (B. Donovan),
[email protected] (J.M. Kaldor), [email protected] (M. Saville).
16 and 18, which are responsible for 70–80% of cervical cancers,
as well as HPV types 6 and 11 which are responsible for almost
all genital warts [1,2]. For a limited two year period from July
2007 to December 2009, females aged 13–26 years were offered
catch-up vaccination through schools, general practitioners (GPs)
and other community based immunization providers [3]. The ongoing national program provides routine school based vaccination to
12–13 year old females and, from 2013, 12–13 year old males with
a two year catch-up for males aged 14–15 years. The quadrivalent and bivalent HPV vaccines have been available on the private
market in Australia since mid 2006 and mid 2007, respectively.
HPV vaccination coverage in Australia is routinely monitored
using a purpose built register, the National HPV Vaccination
0264-410X/$ – see front matter © 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.vaccine.2013.11.075
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J.M.L. Brotherton et al. / Vaccine 32 (2014) 592–597
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of dates and locations of doses received. If no corresponding record
of HPV vaccination could be located in the Register, staff from the
Register contacted the health care provider to seek veriﬁcation of
the reported dose(s).
Analyses: Mobile phone respondents from the pilot study were
combined with respondents from the main study. Women who
reported vaccination but were unsure of the number of doses, were
assumed to have received one dose only in coverage calculations.
For women who consented to have their self reported vaccination
data checked by the Register, the percentage agreement was examined. Vaccine coverage was examined overall and then focused on
women who, on the basis of age, were eligible for catch up vaccination in the community under the national HPV vaccination
program (18–26 years in 2007, corresponding to 22–30 years at
the time of survey in 2011). Descriptive analysis was conducted in
SPSS. Weighting variables were created to adjust the sample to the
national distribution of women by State and age in single years
using Australian Bureau of Statistics (ABS) population estimates
for 2011. Weighted conﬁdence intervals for coverage estimates
were calculated using STATA. Estimates for population subgroups
deﬁned by demographic variables were compared using Pearson
chi squared tests. Odds ratios were adjusted for age.
Coverage was separately estimated using data from the National
HPV Vaccination Program Register, extracted as at 31 March 2013,
for the cohort of women aged 18–26 years in 2007. Two denominators were used when comparing Register data with the estimates
from the CATI survey responses. First were the ABS estimated
resident population (ERP) estimates as at June 2007, as used in previously published results from the catch up program in this age
group [4]. Secondly updated ABS ERP estimates as at June 2011
were used.
The study was approved by the University of New South Wales
Human Research Ethics Committee and access to Register data was
approved by the data custodian, the Commonwealth Department
of Health and Ageing.
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Program Register, established by legislation as part of the program [3]. The Register collects notiﬁcation of HPV vaccinations from
immunization providers, with States and Territories routinely notifying all HPV vaccination episodes from their State school based
programs. GPs and community based providers can report doses
delivered to individuals through either paper based notiﬁcations,
including print outs from practice software, or electronically as
spreadsheets or via a secure web portal directly to the Register [3].
Throughout the two year female catch-up program GPs were paid
$6 per notiﬁcation as an incentive payment.
A good understanding of coverage levels is essential if the population effectiveness of HPV vaccination is to be estimated. However
a one year delay between the commencement of the program
and the establishment of the Register, and the fact that notiﬁcations from community providers were voluntary and required
patient consent, suggest under-notiﬁcation of doses for the adult
women vaccinated in the community [4]. Available data from
the Register show substantial variation in adult vaccine coverage
recorded between States and Territories, suggesting that coverage
data was more completely captured in the jurisdictions with existing state-based vaccination registers (e.g. Queensland); however an
underlying difference in actual vaccination rates between jurisdictions cannot be excluded. New South Wales (NSW), which has the
largest population, has reported coverage that is lower by 10–20%
than the other populous Eastern states of Victoria and Queensland
[4].
In 2011, we conducted a national computer assisted telephone
interview (CATI) survey using random digit dialing of mobile
phones of young women (aged 18–39 years) (the Young Women’s
Reproductive Health Survey). Here we present the ﬁndings for
women eligible for HPV vaccination in the catch-up program with
the aim of providing independent estimates of HPV vaccination
coverage at a national and state level and comparing these results
with those recorded in the Register.
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2. Methods
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Prior to undertaking the survey, we conducted a pilot study
in March 2011 using the same method of dialing, which established the superiority of mobile phones over landlines as a means
of randomly sampling young women in Australia [5]. We therefore conducted the coverage survey using random digit dialing of
mobile phones with recruitment targets stratiﬁed by age and sex
to ensure a representative sample with adequate power.
The CATI survey was conducted between August and December
2011 under a contract with the Hunter Valley Research Foundation, which trained telephone interviewers following standard
scripts. Questions were adapted from previous standardized questions used in Australian sexual health surveys, and included in the
pilot study. The sample of phone numbers was generated using
listed mobile numbers in a composite electronic residential phone
number database, with a random sample drawn and number sufﬁxes altered. These numbers were matched with a major business
directory database to eliminate known business numbers.
Women were eligible for the survey if they were aged 18–39
years and able to communicate verbally in English. If a selected
phone number was unanswered when called, up to three messages
were left on different days requesting a callback to complete the
survey on a free call number.
Study participants who said that they had or may have received
the HPV vaccine were asked if they would consent to having
their vaccination details checked in the National HPV Vaccination Program Register and, where necessary, with their health
care provider. These women were sent a form requesting consent,
demographic details to allow checking on the Register, and details
3. Results
In the main study, 2836 eligible women were identiﬁed (2.9%
of 97,463 numbers dialed) of whom 2269 completed an interview (participation rate 80.0%). Of the other numbers called, the
most frequent outcomes were male respondent (23.8%), answering machine (22.3%), woman of ineligible age (16.0%), disconnected
(15.4%), no answer (8.9%), engaged (8.0%) and business numbers
(1.8%). Initial refusals before screening for eligibility occurred in
0.2% of cases. Taking into account calls to numbers where eligibility
was unknown [5] (40% of calls e.g. unanswered calls or answering machines), the estimated response rate was 41.7%. Interview
time averaged 9.8 min. With the addition of 128 mobile phone
respondents from the pilot study, given the identical methods and
consistent results, there were 2397 participants in total.
3.1. Validation of self-reported vaccination status
There were 1334 women in the total sample who were vaccinated or unsure. Phone permission to be sent a consent form to
authorize checking of HPV vaccination status by the Register was
given by 1118 (84%). Of these, 223 (20%) returned a signed consent
form (with 11 return to senders). Women who returned the consent
form were older (mean 24.95 vs 23.77 years; F = 17.843; P < 0.001),
more likely to be English speaking (92% vs 87%; P = 0.03), of higher
educational status (university degree 42% vs 27%; P < 0.001) and
married (26% vs 17%; P = 0.005) than non consent returners.
Overall, of 629 self-reported doses (unsure women who did
not nominate number of doses excluded), 538 doses (85.6%) were
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Table 1
Correlation of self-report and register/provider conﬁrmation of doses for 223 women.
Self reported doses
Number of women with register or provider conﬁrmed doses
1 (n = 7)
2 (n = 12)
3+a (n = 199)
Unsure how many (n = 5)
2
3
Not conﬁrmed
3 (43%)
0
3 (1.5%)
0
0
5 (42%)
2 (1.0%)
0
3 (43%)
7 (58%)
167 (84%)
5 (100%)
1 (14%)
0
27 (14%)
0
One woman reported 4 doses and had three conﬁrmed on the register.
3.3. Association of vaccination with demographic characteristics
Demographic characteristics of the sample and their association with receipt of HPV vaccination (1 or more doses) are reported
in Table 3. Being born in Australia, a permanent resident in 2007,
living in Australia since 2007 and speaking English at home were
all strongly associated with HPV vaccination (P < 0.001). Unmarried women were signiﬁcantly more likely to have been vaccinated
than married women (OR 1.9 (95% CI 1.5–2.5); P < 0.001: adj for age
OR 1.6 (1.3–2.1; P < 0.001)). Although fewer Aboriginal and Torres
Strait Islander (Indigenous) women than non-Indigenous women
reported any HPV vaccination (24/43 55.8% vs 863/1335 64.6%;
P = 0.4), this was not signiﬁcantly different. However course completion rate was signiﬁcantly lower, with 15/24 Indigenous women
(62.5%) reporting 3 doses compared with 718/863 non-Indigenous
women (83.2%); P = 0.008.
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There were 1379 respondents who, on the basis of age, were
eligible for the catch-up vaccination in the community under the
national HPV vaccination program (18–26 years in 2007, corresponding to 22–30 years at the time of survey in 2011). Among
the 1379 women, 888 reported receiving the HPV vaccine (64.4%).
Of those vaccinated, 570 (64.2%) reported receiving quadrivalent
HPV vaccine, 56 (6.3%) the bivalent vaccine and the remaining 262
(29.5%) were unsure which vaccine they received. The vast majority of women reported being vaccinated by a general practitioner
(795 (89.5%) for the ﬁrst dose).
Self-reported HPV vaccination coverage by age and State of residence is summarized and compared with Register data in Table 2
and Fig. 1. The overall estimate weighted for age and State of
residence was 64/59/53% compared with 49/40/28% based on register records using 2011 ABS ERP data, a difference of 15/19/25%
for doses 1/2/3 respectively. Comparing self-reported coverage
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3.2. Vaccination coverage
(any dose) in the three largest States, this was higher amongst
Victorian and Queenslander women than women in New South
Wales (NSW) (67.3% vs 60.8%: OR 1.3 (1.03–1.7); P = 0.03). The
responders in WA reported the lowest HPV vaccination rates and,
despite the relatively small number of respondents (n = 138), this
was signiﬁcantly different to the rate reported by other Australian
women (55.1% vs 65.4.0%: OR 0.7 (0.4–0.9); P = 0.02). There was
no indication from the survey that women in Queensland and the
Northern Territory, the two jurisdictions with State-based vaccination registers, had signiﬁcantly higher vaccination rates than
elsewhere (66.6% vs 63.8%: P = 0.39).
Self reported HPV vaccination rates for dose 1/2/3 among the
491 women aged 18–21 were 81.9/71.9/67.4% (82.5/71.8/67.2%
weighted for age and state), respectively. Only 15 of the 523
women aged 31–39 years reported vaccination with coverage of
2.9/2.3/1.9% (3.2/2.4/2.0% weighted for age and state).
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conﬁrmed. Across the range of dose numbers reported, most
women were vaccinated: the same number of vaccine doses
reported or a greater number were conﬁrmed for 6/7 reporting one
dose (86%), 100% of 12 women reporting two doses, and 167/199
women reporting three doses (84%) (Table 1). Most of the self
reported three dose courses (144; 72%) were in the register prior to
any provider follow up. Similarly, of the ﬁve women who reported
being unsure how many doses they had received, all ﬁve had three
doses recorded in the Register.
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Fig. 1. Three dose HPV vaccination coverage in Australian women aged 18–26 years
in 2007 estimated by three methods (1) self reported telephone interview data from
1379 women in 2011 (2) National HPV Vaccination Program Register data 2007 ABS
ERP denominator. (a) For women aged 18–26 in 2007, using Australian Bureau of
Statistics Estimated Resident Population data for June 2007 as the denominator.
These women were age eligible for the community based HPV vaccination catch-up
program. Data as held at 31/3/2013. (3) National HPV Vaccination Program Register
data 2011 ABS ERP denominator. (b) For women aged 22–30 in 2011, using Australian Bureau of Statistics Estimated Resident Population data for June 2011 as the
denominator. These women were aged 18–26 in 2007, and were thus age eligible for
the community based HPV vaccination catch-up program. Data as held at 31/3/2013.
3.4. Incomplete vaccination
Of 133 women who reported receipt of only 1 or 2 doses, 43
(32%) reported planning to complete the course. The most common reasons given for not having completed yet were lack of time
(n = 12), pregnancy (n = 8), forgetting (n = 7) and being away/moving
(n = 5). There were 70 (53%) women who did not plan on getting
further doses and 25 (15%) were unsure. The most common reasons given for not planning on receiving more were being unsure
of the beneﬁt of more doses (26%; 18) or being unaware three doses
were needed (16%; 11), and vaccine no longer being free/costing too
much (16%; 11). There were six women (8.5%) who reported that
their doctor advised them against further doses.
4. Discussion
Our estimates of HPV vaccination coverage amongst young adult
women in Australia’s 2007–2009 catch-up program of 64/59/53%
for dose 1/2/3 are respectively 9/14/21% higher than estimated
by the Register (using 2007 population estimates) immediately
after the catch-up program. The discrepancy in estimates could
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Table 2
Self-reported HPV vaccination coverage by age and state of residence compared with National HPV Vaccination Program Register data.
NHVPR coverage 2007
denominator (%) dose 1/2/3a
NHVPR coverage 2011
denominator (%) dose 1/2/3b
Age
22 years (n = 142)
23 years (n = 155)
24 years (n = 143)
25 years (n = 168)
26 years (n = 150)
27 years (n = 146)
28 years (n = 141)
29 years (n = 171)
30 years (n = 163)
Age 22–30 (n = 1379)
73.2/70.4/62.0%
63.9/56.1/48.4%
71.3/68.5/62.9%
69.6/63.1/58.9%
72.0/65.3/58.0%
66.4/58.9/52.1%
66.0/61.7/56.0%
53.2/47.4/45.6%
47.2/42.3/57.0%
64.4/58.9/53.2%
66.1/55.3/41.2%
61.9/50.6/36.2%
60.2/49.0/34.6%
58.5/47.4/33.3%
57.6/46.7/32.7%
57.1/46.3/32.6%
55.6/45.2/31.9%
48.7/39.7/28.3%
29.7/24.1/16.8%
55.0/44.8/31.9%
57.6/48.2/35.9%
53.8/43.9/31.4%
52.6/42.9/30.2%
51.8/42.0/29.5%
51.2/41.4/29.0%
51.0/41.3/29.1%
49.8/40.5/28.6%
43.7/35.6/25.3%
26.7/21.7/15.2%
48.7/39.7/28.3%
State/territory of residencec
ACT n = 28 (2.0%)
NSW n = 431 (31.3%)
NT n = 12 (0.9%)
QLD n = 278 (20.2%)
SA n = 94 (6.8%)
TAS n = 37 (2.7%)
VIC n = 361 (26.2%)
WA n = 138 (10.0%)
All (n = 1379)
75.0/71.4/64.3%
60.8/55.7/49.9%
66.7/58.3/50.0%
66.5/59.7/54.0%
72.3/68.1/62.8%
62.2/43.2/40.5%
67.9/62.9/56.2%
55.1/52.2/49.3%
64.4/58.9/53.2%
46.9/38.1/27.8%
48.0/37.4/26.5%
57.9/46.8/34.2%
63.8/53.2/33.6%
58.6/47.8/33.8%
56.8/46.9/35.0%
57.8/48.5/37.2%
49.5/40.4/30.3%
55.0/44.8/31.9%
48.7/39.5/28.9%
42.7/33.3/23.5%
49.3/39.8/29.1%
56.6/47.2/29.8%
55.5/45.2/31.9%
58.0/47.9/35.7%
50.0/42.0/32.2%
42.6/34.7/26.0%
48.7/39.7/28.3%
Dose 1 64.0% (95% CI 61.2–66.7%)
Dose 2 58.7% (95% CI 55.8–61.5%)
Dose 3 52.8% (95% CI 49.9–55.6%)
Dose 1 55.0% (95% CI 54.9–55.0%)
Dose 2 44.8% (95% CI 44.8–44.9%)
Dose 3 31.9% (95% CI 31.8–32.0%)
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Adjusted for age and
State of residence
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CATI survey self reported coverage
(%) dose 1/2/3
Variable (CATI number (%))
Dose 1 48.7% (95% CI 48.6–48.8%)
Dose 2 39.7% (95% CI 39.7–39.8%)
Dose 3 28.3% (95% CI 28.2–28.3%)
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a
For women aged 18–26 in 2007, using Australian Bureau of Statistics Estimated Resident Population data for June 2007 as the denominator. These women were age
eligible for the community based HPV vaccination catch-up program. Data as held at 31/3/2013.
b
For women aged 22–30 in 2011, using Australian Bureau of Statistics Estimated Resident Population data for June 2011 as the denominator. These women were aged
18–26 in 2007, and were thus age eligible for the community based HPV vaccination catch-up program. Data as held at 31/3/2013.
c
State and Territory abbreviations are: ACT, Australian Capital Territory; NSW, New South Wales; NT, Northern Territory; QLD, Queensland; SA, South Australia; TAS,
Tasmania; VIC, Victoria; WA, Western Australia.
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be even higher, given the large increase in the estimated resident
population of young women over time (Fig. 1). The survey conﬁrms the under-reporting of doses administered in the community
during the catch-up program and suggests that the degree of underreporting varied by dose, with the third dose much less likely to
be notiﬁed than the ﬁrst. Despite the limitations of smaller sample sizes for the less populous States, we did ﬁnd some signiﬁcant
differences in coverage between the jurisdictions, consistent with
Register data. Despite four years having passed between the start
of the catch-up vaccination program and the survey, self-reporting
was reasonably accurate, with 86% of doses able to be conﬁrmed.
The degree of under-reporting suggested by the survey is large
but not inconsistent with previous estimates. A Victorian population based survey undertaken in May 2009 found that, although
the catch-up program was not complete at that stage, self reported
coverage in the community catch-up cohort was 74/69/56% [6]. The
higher coverage notiﬁed in the cohort in Queensland, as compared
with jurisdictions without State based vaccination registers (by up
to 15%), also suggested under-reporting by the other States [4]. In
the present study we did not ﬁnd a signiﬁcantly higher level of coverage in Queensland. Dose distribution data at the end of the catchup program also suggested under-notiﬁcation to the Register, with
volumes of notiﬁcations representing 74–86% of distributed doses
by State [4]. Our survey was able to conﬁrm a slightly lower rate
of vaccination in NSW as compared with Victoria and Queensland (by around 5% for dose 1). One possible explanation could
be that, following an investigation which detected a higher than
anticipated rate of anaphylaxis occurring after HPV vaccination in
schools in NSW [7], community (non-GP) clinics in NSW, where
vaccines are not routinely given in large volumes, were not provided with HPV vaccine. Thus young women who access this type of
service (e.g. family planning clinics) rather than GPs would not have
had access to opportunistic HPV vaccination. Clearly however there
was signiﬁcant under-reporting to the Register from NSW. We also
found that coverage in WA was signiﬁcantly lower than elsewhere,
suggesting that under reporting to the Register by WA providers
does not wholly account for the difference recorded on the Register.
Of note is the degree to which the estimated resident population
is growing in the age cohort vaccinated due to net immigration–the
population of women has grown by 169,000 from 1,312,500 in 2007
to 1,481,500 in 2011. This has correspondingly reduced apparent
vaccination coverage by about 5% per dose to only 49/40/28%. We
found that women who were not born in Australia, were not permanent residents in 2007, were not resident in Australia from 2007
and non-English speaking at home were all much less likely to have
been vaccinated. Married women were also less likely to be vaccinated, perhaps reﬂecting their perception of lower HPV risk. In
relation to incompletely vaccinated women, side effects and safety
concerns were not the primary reason for non-completion. Rather
lack of awareness of the need for further doses, cost to complete
now the free program is ﬁnished, and practical barriers such as
pregnancy, travel and lack of time were important.
The strengths of our study are the large numbers of participants, with a high response rate once an eligible woman was
contacted, recruited using mobile phones. The validation component provides reassurance that self-reported vaccination status is a
reasonable measure in the survey. It is probable that some women
for whom doses could not be conﬁrmed were in fact vaccinated
and that the time delay between administration and follow up
of doses was problematic in some cases as doctors or clinics had
moved or women’s recall of place of vaccination may have been
inaccurate. The participation rate in the survey was comparable
to other mobile phone surveys in similar populations [8] and the
women responding had some similar characteristics to that found
in age-equivalent data from the census [5]. However we acknowledge that it is possible that responders to mobile phone surveys
could be more likely to be vaccinated than other women. Interestingly we found that there was no difference in vaccine coverage
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HPV vaccination receivedb n (%)
Odds ratio (95% CI)
P value
Adjustedc odds ratio
(95% CI)
P value
Born in Australia
Yes 1000 (72.6%)
No 377 (27.4%)
756 (76.1%)
131 (35.0%)
5.9 (4.6–7.7)
1.0 (ref)
P < 0.001
5.9 (4.5–7.6)
P < 0.001
Permanent resident in 2007
Yes 1202 (87.4%)
No 174 (12.6%)
865 (72.5%)
23 (13.3%)
17.2 (10.9–27.2)
1.0 (ref)
P < 0.001
19.1 (12–30)
P < 0.001
Living in Australia since 2007
Yes 1273 (92.4%)
No 104 (7.6%)
854 (67.6%)
34 (32.7%)
4.3 (2.8–6.6)
1.0 (ref)
P < 0.001
4.5 (2.9–7.0)
P < 0.001
Language other than English at home
Yes 337 (24.4%)
No 1042 (75.6%)
128 (38.6%)
759 (73.3%)
0.23 (0.18–0.30)
1.0 (ref)
P < 0.001
0.23 (0.17–0.29)
P < 0.001
Highest education qualiﬁcation
School certiﬁcate 116 (8.4%)
Technical/trade certif. 104 (7.6%)
Higher school certiﬁcate 331 (24.0%)
College certif./diploma 229 (16.6%)
University degree or higher 597 (43.3%)
69 (60.5%)
78 (75.7%)
212 (64.8%)
159 (69.7%)
369 (62.0%)
0.94 (0.62–1.4)
1.9 (1.2–3.1)
1.1 (0.85–1.5)
1.4 (1.02–2.0)
1.0 (ref)
P = 0.03
0.88 (0.6–1.3)
1.9 (1.2–3.1)
1.0 (0.76–1.4)
1.4 (0.98–1.9)
1.0 (ref)
P = 0.03
Relationship status
Single 432 (31.3%)
Casual relationship/s 39 (2.8%)
Committed, not living together 161 (11.7%)
Committed living together not married 321 (23.3%)
Married 425 (30.8%)
280 (65.0%)
25 (67.6%)
126 (78.3%)
229 (71.8%)
227 (54.0%)
1.6 (1.2–2.1)
1.8 (0.87–3.6)
3.1 (2.0–4.7)
2.2 (1.6–3.0)
1.0 (ref)
P < 0.001
1.3 (0.98–1.8)
1.5 (0.7–3.0)
2.5 (1.6–3.9)
1.9 (1.3–2.6)
1.0 (ref)
P < 0.001
Identify as Aboriginal or Torres Strait Islander
Yes 43 (3.1%)
No 1335 (96.9%)
24 (58.5%)
863 (65.0%)
P = 0.39
0.72 (0.38–1.4)
P = 0.32
Have landline at home
Yes 687 (49.9%)
No 690 (50.1%)
443 (64.9%)
444 (64.9%)
P = 0.98
1.05 (0.8–1.3)
P = 0.6
or
C
ad
0.76 (0.40–1.4)
1.0 (ref)
1.0 (0.8–1.2)
1.0 (ref)
or
iz
c
Missing responses excluded.
Unsure responses excluded.
Adjusted for age.
ut
a
b
DR
Demographic variablea n (%)
ap
Table 3
Demographic characteristics and their association with self-reported receipt of HPV vaccination (crude and adjusted for age) amongst 1379 Australian women (age 22–30 in
2011, eligible for the community based HPV vaccination catch-up program 2007–2009).
Co
pi
aa
according to whether or not they had a ﬁxed line phone at home
(Table 3). We were able to recruit 43 Indigenous women in the
vaccination eligible age group (3.1% of the sample), which may
have been an advantage of using mobile phone contact rather than
landlines [5]. Although not a large enough sample to indicate coverage with certainty, the completion rates for these women were
lower, suggesting that the ongoing program should ensure sufﬁcient ﬂexibility and resources to identify and follow up Indigenous
participants to maximize the chances of course completion. This
ﬁnding is in agreement with Register data for Indigenous participants in Queensland [9]. Study limitations include: the small
sample size in the less populous states, the four year time interval between the start of the program and the survey, which could
have adversely impacted upon recall, and that not all women participated in the validation study. This may have resulted in an
overestimate of the validity of self-report.
Our ﬁndings mean that studies which base vaccination status
upon data held by the Register in the catch-up age group need to be
aware that some apparently unvaccinated women are in fact vaccinated, and that some apparently incompletely vaccinated women
are fully vaccinated. Such measurement error will bias vaccine
effectiveness estimates to the null. Coverage data received and held
by the Register for the ongoing program is far more complete, given
that all school programs routinely report data to the Register. There
may still be a small component of under notiﬁcation of doses that
are given in general practice if they are missed at school. The Register sends statements to vaccine recipients who are not completely
vaccinated according to register records and this often results in
notiﬁcation of further doses given in general practice that were not
initially notiﬁed [10]. This study gives the most robust estimates to
date of the extent of under notiﬁcation of HPV vaccination to the
Register during Australia’s catch-up program.
Disclosure
BD receives funding from bioCSL Pty Ltd and BD and JK receive
funding from the Australian Government Department of Health for
HPV surveillance. BD has received speaker’s honoraria from Merck
and SPMSD. JMLB and MS were partner investigators on an Australian Research Council Linkage Grant on which CSL was a partner
organization. BL owns shares in bioCSL.
Acknowledgements
The authors thank staff at the National HPV Vaccination Program
Register: Daniela Petrovski, Jennifer Ngyugen, Genevieve Chappell
and Hunter Valley Research Foundation.
The National HPV Vaccination Program Register is owned by
the Department of Health and Ageing and managed by VCS Inc.
This study was funded by the Australian National Health and Medical Research Council (NHMRC) grant no. 568971 and the Victorian
Cytology Service. BL, BD and JK are supported by NHMRC fellowships.
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