Global impact and cost-effectiveness of one-dose versus two-dose human papillomavirus vaccination schedules: a comparative modelling analysis

BACKGROUND

To eliminate cervical cancer as a public health problem, the World Health Organization had recommended routine vaccination of adolescent girls with two doses of the human papillomavirus (HPV) vaccine before sexual initiation. However, many countries have yet to implement HPV vaccination because of financial or logistical barriers to delivering two doses outside the infant immunisation programme.

METHODS

Using three independent HPV transmission models, we estimated the long-term health benefits and cost-effectiveness of one-dose versus two-dose HPV vaccination, in 188 countries, under scenarios in which one dose of the vaccine gives either a shorter duration of full protection (20 or 30 years) or lifelong protection but lower vaccine efficacy (e.g. 80%) compared to two doses. We simulated routine vaccination with the 9-valent HPV vaccine in 10-year-old girls at 80% coverage for the years 2021-2120, with a 1-year catch-up campaign up to age 14 at 80% coverage in the first year of the programme.

RESULTS

Over the years 2021-2120, one-dose vaccination at 80% coverage was projected to avert 115.2 million (range of medians: 85.1-130.4) and 146.8 million (114.1-161.6) cervical cancers assuming one dose of the vaccine confers 20 and 30 years of protection, respectively. Should one dose of the vaccine provide lifelong protection at 80% vaccine efficacy, 147.8 million (140.6-169.7) cervical cancer cases could be prevented. If protection wanes after 20 years, 65 to 889 additional girls would need to be vaccinated with the second dose to prevent one cervical cancer, depending on the epidemiological profiles of the country. Across all income groups, the threshold cost for the second dose was low: from 1.59 (0.14-3.82) USD in low-income countries to 44.83 (3.75-85.64) USD in high-income countries, assuming one dose confers 30-year protection.

CONCLUSIONS

Results were consistent across the three independent models and suggest that one-dose vaccination has similar health benefits to a two-dose programme while simplifying vaccine delivery, reducing costs, and alleviating vaccine supply constraints. The second dose may become cost-effective if there is a shorter duration of protection from one dose, cheaper vaccine and vaccination delivery strategies, and high burden of cervical cancer.

Modelling the impact of COVID-19 and routine MenACWY vaccination on meningococcal carriage and disease in the UK

Country-wide social distancing and suspension of non-emergency medical care due to the COVID-19 pandemic will undoubtedly have affected public health in multiple ways. While non-pharmaceutical interventions are expected to reduce the transmission of several infectious diseases, severe disruptions to healthcare systems have hampered diagnosis, treatment, and routine vaccination. We examined the effect of this disruption on meningococcal disease and vaccination in the UK. By adapting an existing mathematical model for meningococcal carriage, we addressed the following questions: What is the predicted impact of the existing MenACWY adolescent vaccination programme? What effect might social distancing and reduced vaccine uptake both have on future epidemiology? Will catch-up vaccination campaigns be necessary? Our model indicated that the MenACWY vaccine programme was generating substantial indirect protection and suppressing transmission by 2020. COVID-19 social distancing is expected to have accelerated this decline, causing significant long-lasting reductions in both carriage prevalence of meningococcal A/C/W/Y strains and incidence of invasive meningococcal disease. In all scenarios modelled, pandemic social mixing effects outweighed potential reductions in vaccine uptake, causing an overall decline in carriage prevalence from 2020 for at least 5 years. Model outputs show strong consistency with recently published case data for England.

Modelling: Understanding pandemics and how to control them

New disease challenges, societal demands and better or novel types of data, drive innovations in the structure, formulation and analysis of epidemic models. Innovations in modelling can lead to new insights into epidemic processes and better use of available data, yielding improved disease control and stimulating collection of better data and new data types. Here we identify key challenges for the structure, formulation, analysis and use of mathematical models of pathogen transmission relevant to current and future pandemics.

Challenges on the interaction of models and policy for pandemic control

The COVID-19 pandemic has seen infectious disease modelling at the forefront of government decision-making. Models have been widely used throughout the pandemic to estimate pathogen spread and explore the potential impact of different intervention strategies. Infectious disease modellers and policymakers have worked effectively together, but there are many avenues for progress on this interface. In this paper, we identify and discuss seven broad challenges on the interaction of models and policy for pandemic control. We then conclude with suggestions and recommendations for the future.

Twice-Daily Insulin Regimens in Management of Severe Diabetes

Diurnal glucose profiles have been compared in ten insulin dependent diabetics receiving, firstly, a twice-daily soluble insulin (SI): isophane insulin (NPHI) regimen containing a high proportion of SI (mean 73%) and, secondly, Mixtard insulin (30% SI, 70% NPHI). For each patient the two regimens gave similar profiles though nocturnal blood glucose control was better on Mixtard. HbA1 values were similar on the two regimens. The findings show that, using highly purified formulations, small changes in insulin proportions in twice-daily SI: NPHI regimens may be irrelevant to diabetic control; they also suggest that highly purified NPHI may have a substantially shorter duration of action than its older counterpart and that the convenient regimen of twice-daily Mixtard is usually as good as any more complicated ‘tailormade’ regimen of highly purified insulins.

Expression of bcl-2 protein in nephroblastomas

Bcl-2 expression has been shown to relate to prognosis in several neoplasms. A study of 139 cases of nephroblastomas was undertaken to ascertain the prognostic value of bcl-2 immunoexpression. Archival formalin-fixed, paraffin-embedded tissue sections were stained with monoclonal anti-bcl-2 antibody using a peroxidase-labelled streptavidin biotin kit. 75.5% of cases showed bcl-2 immunoreactivity, however, heterogeneous staining was observed within each case. No statistically significant correlation was found when bcl-2 expression was compared to histology (P=0.451), disease status (P=0.375) and disease stage (P=0.875). A statistically significant difference in bcl-2 protein was noted when comparing tumours treated with and those not treated with pre-operative chemotherapy (P=0.002). Further analysis of the cases that were treated with pre-operative chemotherapy showed a striking difference in survival periods between bcl-2 positive (shorter) and negative tumours (longer). Although not statistically significant, we think that this finding requires further investigation in other series. The results of bcl-2 immunoexpression in nephroblastomas may have prognostic implications that impact on patient treatment protocols.

A double-blind trial of captopril or bendrofluazide in newly diagnosed senile hypertension

Hypertension is a major risk factor for stroke and heart disease in the elderly. Eighty-one hypertensive subjects with mild cognitive impairement, aged over 70 years, were drawn from a community screening programme and randomized to either 12.5 mg captopril twice daily or 2.5 mg bendrofluazide daily in a double-blind trial. Subjects were excluded if they had previously received antihypertensive treatment. The mean blood pressure was reduced from 193/101 mmHg to 154/87 mmHg by captopril and from 188/102 mmHg to 151/89 mmHg by bendrofluazide after 24 weeks; there was no significant difference between the two drugs. Seven subjects withdrew due to adverse events. Adverse events occurred more frequently during the 2-week placebo phase than during active treatment with either drug. The only significant detrimental changes in pre-existing conditions were in 3 subjects (2 captopril, 1 bendrofluazide) who were noted to have worsening of their cataracts. One subject on captopril and 4 subjects on bendrofluazide became hypokalaemic. The trial results support the use of captopril as an alternative to bendrofluazide as a first-line antihypertensive agent in the community for elderly people, but large studies are required to measure accurately effects on significant morbidity and mortality.

HIV roundtable. Professional perspectives

As the HIV epidemic escalates, concern is mounting over the implications of infection among health care workers. Should all medical professionals be tested? Should supervisors and/or patients be notified if the results are positive? Should the infected PA continue to practice? What about performing surgery? Should he or she be considered impaired? And what about the long-term stress of working with HIV patients? Experts discuss the AAPA's latest recommendations, and share suggestions on prevention and patient care with the audience.

HIV antibody-positive. A new cause of impairment

The American Academy of Physician Assistants Subcommittee on the Impaired Physician Assistant has begun to receive requests for help from PAs who fear that their ability to practice may be hindered because they are at risk of infection with human immunodeficiency virus (HIV). The American Medical Association and the Centers for Disease Control have already developed some guidelines for all health care providers. The special concerns of PAs are also being addressed by our national leadership. In response to specific concerns by some PAs directly affected, the former chairperson of the Task Force on the Impaired PA helped develop questions that the profession needs to address.

PAs confront "denial disease"

At last year's Annual Conference, the AAPA House of Delegates formally convened, for the first time, a task force to study the problem of chemical dependency among PAs, and to help constituent chapters develop identification and intervention programs. The Task Force on the Impaired PA makes its first report to the HOD at this year's conference. In addition, a special symposium on impaired practitioners is being offered for CME credit. The task force's chairperson reviews efforts made during the past year to raise the profession's awareness of the problem. She focuses on the first-person accounts of six PAs who are recovering alcoholics and addicts (see "The Chemically Dependent PA: Role models for Recovery" on page 115).

My brother's keeper: assisting the impaired PA

Impairment is defined as the inability to practice medicine with reasonable skill and safety to patients because of physical or mental illness, including deterioration through the aging process, loss of motor skills, or excessive use or abuse of drugs, including alcohol. A practitioner is also impaired when personal problems interfere with the administration of medical care. Acknowledging the issue of impairment can be unpleasant. By doing so, practitioners often realize that their perceptions of themselves and their colleagues as invulnerable guardians of public health and healers of disease, are delusions. This growing problem reflects not only on the individual practitioner suffering from impairment, but on the profession as a whole. Thus, the problems of the impaired PA must be addressed in a reasonable and compassionate manner. The authors discuss how to deal with affected colleagues, and outline an alternative, nonpunitive, and humanitarian model for assisting impaired PAs, established by the Michigan Academy of Physician Assistants.

Experiences with physostigmine in the reversal of adverse post-anaesthetic effects

Physostigmine salicylate has proved to be a very useful agent for use in the recovery room. All but two of our first 110 patients receiving it were returned to full consciousness, whether they had been comatose or agitated. In our hands it has been used to reverse the adverse central effects of tranquilizers, antihistamines and belladonna alkaloids.