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Achieving HPV herd immunity cost-effectively. When does it make sense to allocate resources preferentially to boys?

23 Apr, 15 | by Leslie Goode, Blogmaster

Recent empirical studies of HPV vaccination have provided evidence that marginal vaccination costs increase with coverage.  Let us take into account – they argue – not just the vaccine price, but the cost of education and outreach programmes that would be needed so as to reach the yet unvaccinated population.  If we do so, we are likely to find that raising the vaccination rate for pre-adolescent girls, let us say, from 40-41%, proves considerably more expensive than raising it from 20-21%.  This, in turn, raises the question whether – given the achievement of herd immunity is the ultimate goal – resources are necessarily best allocated when directed to the female rather than the male pre-adolescent population. Could it even be that – at certain levels of coverage and a certain rates of increase in marginal vaccination cost (for girls and for boys) – resources might be more effectively allocated to the vaccination of pre-adolescent boys? Ryser & Myers in a recent study seek to model the impact of marginal cost increase in order to answer this question.  In the case of US, at least – with rates of vaccination standing currently, for girls and boys, at, respectively 37% and 13.9% – they argue in cost benefit terms for re-directing resources to boys.  However, the question is no doubt relevant to other countries in which HPV has been introduced, but levels sufficient for herd immunity, have not yet been achieved.

Optimal allocation of new resources as between girls and boys for a given level of vaccination is indicated in the diagrams on p.40.  Marginal vaccination cost increase is estimated at a higher, a lower, and zero level.  What is striking is the radically different patterns of optimal allocation between girls and boys in those three scenarios.  At the very least, the results challenge the orthodoxy of the superior cost benefit of female vaccination. They also indicate the importance of further empirical research into marginal vaccination cost increase.

The limitations of the study are largely due to the assumption of a closed sexual network of 14-18 yr old heterosexual adolescents.  The attempt is made to factor in the impact of various complicating factors, such as the assortativity of vaccine uptake with sexual activity, the likely presence of additional relationships between females inside, and older males outside, the network, and asymmetric vaccination cost curves as between girls and boys.  But the most serious limitation was beyond the power of the study to address.  This is the restriction of the modelled network to heterosexual relations, and the exclusion from consideration of a large number of HPV-related conditions such as anal and oro-pharyngeal cancers which have higher incidence among MSM and HIV-infected individuals (Lawton & Asboe (STIs); English & Pourbohloul (STIs)).  One wonders, therefore, whether the case for male HPV vaccination is not a great deal stronger than might appear from this paper.  At all events, a case is made that, even when these conditions are excluded, a greater allocation of HPV vaccination resources to males may be justifiable – e.g. currently in the US.  For the impact of the recent extension of the HPV vaccination programme to males in Australia (the first country to have taken this step (2013)), see Korostil & Donovan (STIs).

Can financial incentives help address the problem of HIV lost-to-follow-up in the US?

21 Apr, 15 | by Leslie Goode, Blogmaster

An article by Skarbinski & Mermin, discussed in my recent blog, Skarbinski & Mermin (STI/blogs), throws into sharp light the problem of the 45.2% of the HIV/AIDS infected population who are diagnosed but lost to follow-up.  According to their estimate this group are responsible for 61.3% of transmissions.  Various local attempts have been made to address this problem through more “wrap-around” approaches to health care (Bocour & Less (STI/blog)), or through computer assisted self-interviewing (Dombrowski & Golden (STI).  Another approach is the use of financial incentives.  Relatively small-scale and local experiments in various forms of conditional cash transfer have been described by a number of studies recently featured in STIs.  These have aimed, for example, to reduce STIs and pregnancy among Latino youth in San Francisco (Minnis & Padian (STI)), to encourage HIV-infected men to bring their wives for testing in Pakistan (Khan & Khan (STI), to incentivize villagers to remain HIV-free in Lesotho (Bjoerkman-Nyqvist & Svensson (STI)), or to promote syphilis testing amongst indigenous groups in Edmonton, Canada (Gratrix & Talbot (STI)).

Yet what role could financial incentives play in the broader context of mainstream HIV management in the US?  Could they help to address the problem of retention in HIV care across the range of HIV care settings?

A recent US study, HPTN 065 (TLC-Plus) reported at the 2015 Conference on Retroviruses and Opportunistic Infections (CROI) addresses this very question.  It involved two-year RCT in a total of 37 testing sites in Bronx and Washington DC., randomized to an intervention and a control arm.  The intervention offered incentives for both linkage-to-care, and viral suppression.  For linkage-to-care, the incentive consisted in the issue to HIV diagnosed of a $25 coupon redeemable when the participant returned to have blood taken for laboratory tests, and a $100 coupon redeemable when he/she returned for test results and to discuss a long-term care plan.  For viral suppression, it took the form of the issue of a $70 gift card to patients taking medication at the end of every three months if they had an undetectable viral load.  Over the duration of the trial, 1,061 coupons were given for linkage-to-care, and 40,000 gift cards were dispensed to 9,153 patients for viral suppression.

Disappointingly, no overall increase was observed in intervention compared to control settings, either in linkage-to-care or in the proportion of patients achieving viral suppression.  However, the intervention brought significant improvements in viral suppression and continuity of care (completion of four out of five possible visits for tests in last 15 months) within certain specific care settings.  In particular, these were: care settings where <65% of the patients were achieving viral suppression at the start of the study (improvements of 10% overall, 13% as measured in the last three months of the study); small-scale care settings (improvements of 13% as measured in the last three months, and of 19% overall in continuity of care).  The investigators conclude that there may be a role for financial incentives in specific health care settings.

Indiana State ban on Needle Share programmes faces challenge of an IDU-fuelled HIV spike

20 Apr, 15 | by Leslie Goode, Blogmaster

In 2011 18.5% of HIV infections in the US were attributable to intravenous drug-use (IDU) – a significant proportion (Lansky & Wejnert (STIs)).  The issue of IDU fuelled HIV transmission has been brought forcibly to the attention of Americans in the last few weeks by the recent HIV outbreak in Scott County, Indiana, US.  This local epidemic appears to have been the result of the recreational use of the opiate, Opala. The number of infections has continued to rise, reaching a new peak of 130 this last week (Indystar/needle exchange; npr/Indiana’s HIV spike).

The effectiveness of public health interventions amongst IDU, including needle exchange programmes is well-established. Recent studies in Russia and East-European contexts (Vagaitseva & Demyanenko (STIs); Boci & Bani (STIs)), where IDU accounts for greatest proportion of infections,  have also come to very positive conclusions about their cost-effectiveness (Demyanenko & Vagaitseva (STIs).  They have also considered ways of improving uptake among drug-users (Boci & Hallkaj (STIs).  Sadly, in 23 states of the US – as in Russia and some East-European countries – traditional legal restrictions on needle exchange programmes remain in force (LawAtlas/US).  Indiana just happens to be one of these US states.  Its governor, who has had to authorize a short-term moratorium on the legal restriction of needle exchange in response to the outbreak, just happens to be Mike Pence, a republican who is known for his especially hawkish views on social issues (see “US Republicans prepared to put the poor at risk” (STI/blogs)) and favours continuation of the ban.

Needless to say, an order authorizing the temporary suspension of the restrictions on needle exchange was issued last month.  A needle-exchange programme has distributed 5,300 clean needles to drug-users since 8th April when it began its activities.

Unfortunately, however, the temporary suspension is due to expire on 25th April.  It also applies only to Scott County. Health experts are pushing legislators to allow needle exchange in neighbouring counties of Indiana, where high levels of HCV indicate a high risk of similar outbreaks.  On Monday, a joint Senate and House Legislative Committee will consider a measure, authored by Ed Clere, a representative from a neighbouring county, to authorize local public health and law enforcement authorities to work together to start their own need exchange programmes. But Governor Pence has threatened to veto the measure.  He declines to explain his position in public, but is said by Senate President, David Long, to believe that needle exchange programmes lead to greater drug use (News & Tribune/Indiana’s needle exchange bill).

Retention in care rather than diagnosis may prove the ultimate challenge for US HIV response

25 Mar, 15 | by Leslie Goode, Blogmaster

The real challenge which the US HIV/AIDS epidemic poses for the US public health services is not simply to achieve higher levels of diagnosis – but, far more than that, to improve linkage to, and retention in, care.  This claim is hardly controversial. But it is thrown into stark relief in a recent study by Skarbinski & Mermin, which estimates the number of HIV transmissions attributable to non-retention in care for 2009.

The authors employ the notion of a five-phase “care continuum”.  Using population data from the National HIV Surveillance System and medical data from the National HIV Behavioral Surveillance System and the Medical Monitoring Project, they estimate the number of HIV transmissions occurring at each phase.  The phases in the continuum are: (1) infected, but undiagnosed; (2) diagnosed, but not retained in care (attending at least one visit to a medical care provider Jan. – April 2009); (3) diagnosed, retained in care, but not given ART; (4) diagnosed, retained in care, prescribed ART, but not virally suppressed; (5) virally suppressed.

The reduction in attributable transmissions achieved for those diagnosed but not retained in care (phase 2), as compared with those who remain undiagnosed (phase 1), is 19%.  (It is probably due to a decrease in HIV-discordant unprotected sex).  But the reduction achieved for those who achieve viral suppression (phase 5), as compared with those who remain undiagnosed, is 94%.  In estimating the epidemiological impact of these reductions, we need to factor in the percentage of the infected population at each phase.  The large proportion (45.2%) of the HIV infected who are diagnosed but not retained (phase 2) explains the very high proportion of total transmissions (61.3%) attributable to this phase.  By comparison, only 30.2% are attributable to the undiagnosed (phase 1), and 2.5% to the virally suppressed (phase 5).  The low epidemiological impact of those at phases 3 and 4 is due to the relatively low proportion of those infected who remain in these phases.

The message, then, is that achieving greater success in retaining the HIV diagnosed in care may prove the key to combating the epidemic at population level.  Of course, diagnosis remains the indispensable first step.  But the potential gains of diagnosis will be only very partially experienced, so long as such a large proportion of those diagnosed are not retained in care.  Of course, improving retention in care may constitute a somewhat different – and perhaps more difficult – challenge for the US health services from diagnosis.  The specific problems of the US health system in this regard are discussed by Sherer (STI), and the characteristics of individuals “lost to follow up” by Haddow & Mercey (STI) and Lee & Gazzard (STI).  Local attempts to address these problems through a more “wrap-around” approach to health care in the US are described in my blog Bocour & Less (STI/blog) (see Bocour &  Less).  There has also been interest in the computer assisted self-interviewing in order to engage those lost to care (Dombrowski & Golden (STI)).

Reported 86% effectiveness for MSM PrEP by PROUD study makes this intervention a viable option for UK health services

25 Mar, 15 | by Leslie Goode, Blogmaster

The Conference on Retroviruses and Opportunistic Infections has recently taken place.  At that event the UK PROUD (PRe-exposure Option for reducing HIV in the UK: immediate or Deferred) study of pre-exposure prophylaxis (PrEP) for MSM reported its results, prior to publication in the coming months.  The headline figure is an astonishing 86% for the reduction of risk of infection in the intervention group.  Hitherto, results of PrEP trials, largely conducted in Africa, have often been disappointing.  This is probably on account of poor adherence (VOICE D( STI/blog); Haberer & Bangsberg (STI/blog); Hendrix & Bumpus (STI/blog)).  The good result achieved here is no doubt attributable to good adherence.  It demonstrates, as these earlier trials have not, the true effectiveness of PrEP.

The UK trial included 545 participants at 13 practices. 276 were randomized to receive PrEP immediately, while the remaining 269 received it after a year.  Earlier PrEP trials have been blind and placebo-controlled.  But this design had the advantage of demonstrating the effectiveness of PrEP in real life. The participants were aware if they were taking the active drug and could have changed their sexual behaviour accordingly.  Given one of the major concerns around PrEP is that of risk compensation – i.e. taking advantage of the protection of PrEP to engage in more risky behaviour than they would otherwise (Marcus & Grant (STI/blog); Baeten & Celum (STI/blog)) – this was a valuable aspect of the trial.

In the period to October 2014, there were 22 HIV infections – 3 in the immediate, and 19 in the deferred group.  This gives us the headline figure of 86%.  At this point, ethical considerations dictated that the study design be changed so all participants received PrEP from then on.  Initially, this study was intended to be a pilot, and to be followed by a larger scale trial.  The decisiveness of the interim findings, however, led to cancellation of that further study.  (For an interesting commentary on the need for researchers to keep pace with changing ethical parameters, see Cohen & Sugarman (STI/blog)).  Cost-effectiveness analyses are apparently underway.  No details are given in the report.  But evidently the high effectiveness observed in the study will allow investigators to present a far more positive case for PrEP than has been warranted by earlier trials (see Borquez & Hallett (STI); Gomez & Hallett (STI/blog); Cremin & Garnett (STI)).  They are also working with stakeholders on how PrEP services could be commissioned across NHS and local authorities.

The varied nature of the US HIV/AIDS epidemic: what makes the South so different?

27 Feb, 15 | by Leslie Goode, Blogmaster

As of 2011, 38% of all US citizens diagnosed with HIV were from a block of nine states in the south-east, sometimes referred to as “the South”: Louisiana, Alabama, Florida, N. and S. Carolina, Georgia, Texas, Mississippi and Tennessee. Death rates among those living with HIV in this region were, by far, the highest of any US region.  A recent study (Reif & Wilson) uses CDC HIV surveillance data to seek to assign characteristics to the large number of persons in that region diagnosed with, and frequently failing to survive, HIV/AIDS, in order to determine what it is about this region of the US that makes it peculiarly vulnerable to the epidemic.

A number of these characteristics were not specific to the South, but shared by all the southern states: the high proportion of those diagnosed who are female (27%: US average 20.9%), who have contracted HIV through hetero-sexual relations (14.5%: US average 11.7%) and who fall in the 13-24 yr age group. What differentiates the South more particularly, is the considerably higher percentages of diagnoses among those living in rural (11%) and suburban (17%) areas, though even urban rates (29.6 per 100,000) are higher in the South than in other regions.  Five-year survival following AIDS diagnosis, at 73%, is considerably lower than the US average (77%), and lower than for any other region. Survival rates following HIV diagnosis were considerably lower for rural (82%) than for urban (86%) areas.  Above all, the death, rate at 27.3 per 1000, was considerably higher than in any other region of the US. (HIV mortality in the UK fell from 21.8 to 8.2 per 1000 over the years 1997-2008 (Smith & Delpech (STI))).

The high death rates for the South suggest, the authors claim, a fundamental “disconnect” between diagnosis and maintenance of care in the region. Moreover, when the figures are adjusted to take account of characteristics of individuals living with HIV, including sex, race, mode of transmission etc., the disparity remains substantively unchanged or accentuated. This likely indicates underlying structural factors affecting the states of the South.  Obvious candidates would be lower insurance coverage, lower levels of income and education. On the basis of the convergence of high death rates and the high proportion of rural and suburban HIV cases in the region, the authors also evoke, more speculatively, the “class system unique to the US South” which has traditionally allowed little social mobility.  They argue this may have contributed towards a social environment among lower strata characterized by a combination of stigmatization and distrust of medical services, which is very unconducive to retention in care.

Trialling innovative approaches to STI partner services: Partner-Delivered vv. Accelerated Partner Therapy

26 Feb, 15 | by Leslie Goode, Blogmaster

It is vital to treat partners of patients with curable STIs as quickly as possible.  But the effectiveness of interventions to achieve this proves hard to measure – and the case for increasing resources correspondingly difficult to make.  The inadequacy of the resources available to existing partner services has led some investigators in the US and UK to seek out innovative approaches to ensuring the treatment of partners which are less expensive.  One option – Patient-Delivered Partner Therapy (PDPT) – is to provide treatment for partners via the patient and without prior medical assessment of the partner.  The problems with this are: first, that PDPT may not conform to legal (Cramer & Leichliter (STI)) or professional guidelines; second, that concomitant infections (e.g. HIV) in the partner may go undiagnosed and untreated. An alternative solution – Accelerated Partner Therapy (APT) – is to treat the partner via the patient, but only after a medical assessment conducted by telephone or with a pharmacist (Golden & Estcourt (STI); Dombrowski & Golden (STI)).

The option of PDPT has been trialled in various US clinics (Mickievicz & Rietmeijer (STI); Sanchez & Schillinger (STI); but its impact is difficult to evaluate on a local level. Now, for the first time, Golden & Holmes have attempted a population-level randomized control trial of uptake and impact across 23 out of the 25 counties of Washington State.  This impressively large-scale operation had two elements.  The first was the provision of free PDPT, and involved: 1. informing all clinicians about the programme; 2. making stocks of free PDPT available to clinicians who had reported ≥ one case of Chlamydia or Gonorrhoea, and to certain large pharmaceutical chains; 3. visiting clinicians reporting frequent cases for the purpose of educating staff about the programme.  The second element was the possibility offered to diagnosing practitioners via routine report forms of having the provision of partner services handled by the state public health department. This intervention was rolled out in four successive waves to different counties in turn, thus enabling the impact of the intervention to be controlled against the default situation in the counties of each wave.

As regards uptake, percentage of persons receiving PDPT from clinicians rose in intervention periods from 18% to 34%, and percentage receiving partner services from 25% to 45%.  This is broadly comparable with what has been achieved by more local interventions in the US.  Unfortunately, it is one thing for a pack to be accepted by the index patient, another for a partner to be successfully treated.  Hence the interest of G&S’s attempt to evaluate population-level impact – through testing in sentinel clinics in the case of Chlamydia, and through incidence of reported infection in the case of Gonorrhoea. It was undoubtedly ambitious of G&S to seek an indicator of population level impact for a comparatively brief intervention.  It is no surprise that the results are less than overwhelming. Chlamydia test positivity and gonorrhoea incidence in women declined respectively from 8.2% to 6.5% and from 59.6 to 26.4 per 100,000. The latter more impressive reduction is unfortunately hard to distinguish from a strong secular trend in the same direction in various states.

There are more general problems, however – such as knowing whether the handing over of PDPT packs is resulting in the successful treatment of disease, or whether it may even be contributing to an ongoing failure to diagnose concomitant partner infections.  These might weigh in favour of the alternative approach recently developed in UK clinics: APT.  Estcourt & Johnson (STI) report uptakes of 66% and 59% for versions of APT as against 36% for conventional PS.  Sending a treatment pack following a telephone interview would seem to offer a better guarantee of partner treatment, than offering a pack on the basis of nothing more than a stated willingness of the index patient to deliver it.  At the same time, interviewing the partner averts the risk of doing harm by pre-empting consultations at which a fuller diagnosis of the partner’s condition would have been possible.  A population-level trial of the impact of APT has yet to be undertaken.

ChemSex and HCV transmission among UK MSM

2 Feb, 15 | by Leslie Goode, Blogmaster

Reports of substantial rises in the incidence of HCV among MSM populations in the UK  (STI/Yaphe & KleinSTI/Ghosn & Chaix) have attracted some attention in STI journal.  Not least because intravenous drug use is the most obvious mode of transmission for this blood-borne virus, and MSM have in the past tended not to use this route of administration.  The question then arises what specific factors in the environment of these MSM populations are increasing their risk?  The question is all the more urgent as – whatever those factors may be – MSM populations seem as yet largely incapable of reducing them – to judge by the large proportion of successfully treated MSM who become re-infected within two years (40% according to a N. London hospital). A number of recent contributions to STI journal consider the role of MSM sex in HCV transmission (STI/Stall & McFarland; STI/Valencia & Salas), and what it is in the practices or lifestyle of MSM that puts them at particular risk. Associations have been identified with number of partners, casual anal sex, sex parties (STI/Marcellin & Spire): specific practices such as fisting, rimming, recreational use of intra-nasal drugs (STIs/Turner & Stephenson): interactions between these practices and certain self-described MSM lifestyle groups such as “leather”, or “lycra & rubber” (STI/Matser & van der Loeff).

A recently published guide for health professionals (ChemSex & Hepatitis C), claiming to be based on c.500 conversations with MSM clients, offers an illuminating, ground-level account of one risk environment: events involving “ChemSex”, or the collective use of recreational drugs to enhance sexual experience. The authors claim that ChemSex parties are a growing HCV risk for MSM for three reasons: greater availability of certain non-injection drugs; increased injecting drug use; more widespread use of smartphone Apps and online “hooking-up” sites.  MSM involved in Chemsex, they claim, are a particularly hard-to-reach group for health professionals because of their use of informal private venues (rather than clubs, or the street), and a lack of exposure and openness to IDU service messages owing to a past preference among MSM for non-intravenous drugs.

Before health professionals can communicate effectively with these clients about the potentially stigma-laden issue of HCV they need to develop an awareness of the various elements of risk in the ChemSex environment.     The booklet aims to guide health professionals on this path. This it is does by means of an illustrative “case study”, as well as by a systematic itemization of potential risk factors in the ChemSex environment, including some less obvious transmission routes  – such as blood on douching tools or shower hoses, or blood on the lube pump, or snorting straw.   Language, of course, is at the heart of communication.  The booket, therefore, includes a handy list of current popular terms, as well as suggested  questions to ask at consultations.

Should the Faculty of Sexual and Reproductive Health and Keele University Postgraduate Award in Medical Education be compulsory for GUM trainees?

30 Jan, 15 | by Leslie Goode, Blogmaster

Author: Dr Zana Ladipo, New Croft Sexual Health Centre, The Newcastle Upon Tyne Hospitals NHS Foundation Trust, Newcastle, UK

Sexual Health services in the United Kingdom are changing from separate Genitourinary Medicine (GUM) clinics and Faculty of Sexual and Reproductive Health (FSRH) clinics to a more integrated Sexual Health service, a one-stop shop for patients. There is now a debate as to whether this may lead to a loss of expertise1 and whether it will improve patient care2 -3 and provide more career opportunities for staff.1 Of particular concern is a difference between the two career tracks in the respective opportunities they offer to acquire teaching training skills.

On the FSRH side, trainees are required to have passed their Diploma in FSRH (DFSRH) and their membership exams, and, with the planned merging of the services, are increasingly being advised to obtain the Diploma in GUM. But they have also been required to do the FSRH & Keele University Post Graduate Award in medical education (PGA Med Ed).

On the GUM side, trainees are required to achieve the GUM, HIV and FSRH diplomas.  But only some pursue a qualification in medical education, e.g. the Royal College of Physicians Certificate in Medical Education.  This represents a significant disadvantage for GUM trainees. It isn’t just that the PGA Med Ed improves teaching and feedback skills: it also enables the graduate to become a Faculty Registered Trainer (FRT) and train others towards obtaining the DFSRH, which is a compulsory qualification for both GUM and FSRH trainees. Doctors and nurses in all specialities are required to take on roles involving increasing amounts of medical education.4 Most have little formal training in this area.  In these times of austerity and budget cuts, offering training towards the DFSRH can be a useful way for a clinic to generate revenue by attracting external paying candidates as well as providing local training.

Most importantly, however, without the PGA Med Ed, GUM trainees cannot obtain FRT status. I have spoken about the PGA Med Ed to other GUM trainees, all of whom were unaware of this. Only one other GUM doctor and I attended the course in March 2014, and I think this may be due more to lack of knowledge about the course among GUM trainees rather than a lack of interest. I do not feel it should be compulsory for GUM trainees, but simply aim to increase awareness of its availability and usefulness. Information on the course can be found at the FSRH website (http://www.fsrh.org/) under ‘Training’. I hope that after reading this letter you agree that the PGA Med Ed is a worthwhile qualification for GUM specialists working in or starting an integrated service.

Dr Zana Ladipo

 

REFERENCE LIST

  1. French RS, Coope CM, Graham A, et al. One stop shop versus collaborative integration: what is the best way of delivering sexual health services?  Sex Transm Infect 2006,82;3:202-6 (STIs/French&Graham)
  2. Dawson, SG, Callander N, Roche C, et al. Integrated sexual health care: the development and review of one model of service delivery. Int J STD AIDS 2000;11:428-34 (Dawson&Roche)
  3. Kinn S, MacDonald C, Hinks S, et al. Clients and staff views on facilities and services, before and after the convergence of sexual, reproductive and women’s services. Eur J Contracept Reprod Health Care 2003;8:65-74 (Kinn&Hinks)
  4. Hutchinson, L. ABC of learning and teaching: Educational environment. BMJ 2003;326:810 (Hutchinson)

 

 

Population-based study concludes: HPV vaccination does not cause sexual disinhibition

19 Jan, 15 | by Leslie Goode, Blogmaster

HPV is known to be the cause of various types of cancer, including cervical cancer. Routine vaccination before the onset of sexual activity ought therefore to be effective in reducing the incidence of these cancers, and has been adopted by many countries.  The impact of such programmes will not be apparent for years; but the sharp reduction of cases of genital warts in several countries where vaccination has been introduced, is an encouraging indicator of the likely effectiveness of cancer prevention over the longer term (STI/blog/Smith & Canfell).  Unfortunately, however, vaccination coverage has often been sub-optimal ( STI/Sacks & Robinson).  A number of recent contributions to STIs have attempted to identify parental (and provider) concerns that may be responsible for poor uptake of vaccination (STI/Schuler & Brewer; STI/Javanbakht & Guerry;  STI/Krupp & Madhivanan).

One concern frequently mentioned by these studies is that HPV vaccination could lead to sexual disinhibition.  The results of a large population-based cohort study in Canada (Smith & Levesque (S&M)), where HPV vaccination was introduced in 2006, may help to offer some assurance on this matter.  The study was based on administrative health data relating to a cohort of 260,493 girls, of whom approximately half were in the first two school year-groups offered the vaccine (2006-7; 2007-8), and the other half in the previous two year groups (2004-5;2005-6). The study compared data from the two groups in respect to the incidence of pregnancy and non-HPV-related STIs over the four years following vaccination.  Earlier studies addressing the question of vaccination-related disinhibition have focussed on risk perception or reported sexual behaviour.   S&M use objective medical outcomes – pregnancy and STi diagnoses.  Moreover, the definition of the groups on the basis of eligibility for vaccination, as opposed to vaccination itself, circumvents the potential confounding bias which might have been expected to arise from the fact that the same beliefs and behaviours influencing the decision to vaccinate would likely also have affected the outcome of pregnancy and STI infection.

The results are entirely reassuring.  In respect to pregnancy they show precisely no difference between the eligible as opposed to ineligible girls (RR = 1.0 0); in regard to non-HPV related STI diagnoses, they show a small reduction among eligible girls, which the authors plausibly attribute to the likely eventuality of some HPV-related warts having being categorized in the data as non-HPV-related.  These findings corroborate, on a population wide basis, those of earlier studies (e.g. Bednarczyk & Omer) which indicate that fears of vaccination-related disinhibition are unwarranted.

 

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