Is 1 dose of HPV vaccine as effective as 3?

June 17, 2015

A new study examines the efficacy of a single dose of the HPV vaccine for preventions. Plus: What's the optimal time for inserting a contraceptive implant after delivery? And: A case study wonders if NIPT can help diagnose cancer in the mother.

Just 1 dose of the human papillomavirus (HPV) vaccine may provide protection against HPV-16/18 similar to the 3-dose schedule, according to results from 2 clinical trials. If the outcomes hold true in further study, the investigators said, a 1-dose approach might help overcome barriers to vaccine uptake in many regions of the world.

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Researchers used data from the Costa Rica Vaccine Trial and the PATRICIA trial, which were both Phase III, double-blind, randomized controlled clinical trials of the HPV-16/18 AS04-adjuvanted vaccine in adolescent and young adult women. Women with less than 12 months of follow-up or those who were HPV-16- or HPV-18- DNA-positive at the time of enrollment were excluded from calculations. The researchers calculated the vaccine efficacy against a 1-time detection of incident HPV infections after 1, 2, or 3 doses of the vaccine.

In the cohort, 22,327 of the women received all 3 doses, 1185 received 2 doses, and 543 received 1 dose. The efficacy of the vaccine against incident HPV-16/18 infections for 3 doses was 77.0% (95% confidence interval [CI] 74.7 – 79.1), for 2 doses it was 76.0% (62.0 – 85.3), and for 1 dose it was 85.7% (70.7 – 93.7). Efficacy of the vaccine against incident HPV-31/33/45 infections was 59.7% (56.0 – 63.0) for 3 doses, 37.7% (12.4 – 55.9) for 2 doses, and 36.6% (-5.4 to 62.2) for 1 dose. The investigators noted that some of the outcomes might have resulted from undetected infections present before vaccination, which explains why efficacy estimates for this endpoint are generally lower than those for persistent infection. 

For women who received 2 doses, the vaccine efficacy against incident HPV-16/18 was 75.3% (54.2 – 87.5) when the second dose was administered at 1 month; it was 82.6% (42.3 – 96.1) for those who received the second dose at 6 months. For HPV-31/33/45, vaccine efficacy for those who received their second dose at 6 months (68.1%, 27.0–87.0) was similar to those who received all 3 doses.

The investigators found that in women aged 15 to 25, at 4 years after vaccination, 1 or 2 doses of HPV16/18 vaccine appeared to provide protection similar to a 3-dose schedule. For those receiving 2 doses, having the 2 shots separated by 6 months provided some extra cross-protection. They believe that further research is warranted about the efficacy of 1 dose for protecting against HPV-16/18.

NEXT: What's the optimal time to insert a contraceptive implant postpartum?


Does time equal money with insertion of a contraceptive implant?

The timing of insertion of a contraceptive implant after delivery may have a significant impact on health care costs, according to results of a new decision-analytic model. For every 1,000 women using the devices postpartum, the authors say, immediate versus delayed placement could avert 191 unintended pregnancies and save $1.2 million in health system expenditures.

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Published in Obstetrics & Gynecology, the findings are by investigators from Yale School of Medicine and the University of California, Irvine. They looked at a hypothetical population of women who requested an etonogestrel implant postpartum, with a timeframe for insertion from delivery to 1 year thereafter. Model inputs were derived from a comprehensive literature review.

The authors compared implant insertion before a woman was discharged following delivery with insertion at the first postpartum office visit, from the perspective of a health care system. Their model included implant insertion and removal, loss to follow up at the postpartum visit, use of alternative contraceptive methods, and contraceptive failure. Incremental costs of immediate insertion for each pregnancy prevented during the first postpartum year and cost savings associated with pregnancies prevented were calculated. One-way sensitivity analyses also were performed.

Immediate postpartum implant insertion was found to cost $1,091 per patient but result in an expected pregnancy rate of 2.4%, compared with $650 for delayed insertion and an expected pregnancy rate of 21.6%. That resulted in an incremental cost-effectiveness ratio of $2,304 per pregnancy prevented, and a savings of $1,263 per patient, given medical costs of unintended pregnancies that could be avoided.

The investigators noted that their analysis was for only 1 year postpartum, whereas the implant can be used for up to 3 years. They believe that the findings would be even more favorable, were their model extended for another 2 years. “Immediate postpartum insertion of the contraceptive implant,” they said, “is expected to be cost-effective compared with delayed insertion and to result in a decrease in unintended pregnancy and net savings for the health care system in the long run. Effort should be made to offer the contraceptive implant in the immediate postpartum period to all women who desire it and do not have contraindications.” 

NEXT: Can NIPT detect maternal cancers?


NIPT may detect maternal cancer

A trio of cases presented in JAMA Oncology indicate that noninvasive prenatal testing (NIPT) may provide even more benefit than previously thought by identifying maternal cancers. The Belgian authors believe theirs is the first report of aberrant NIPT results that ultimately led to cancer diagnosis.

In the series, NIPT with parallel sequencing was performed routinely on more than 4000 women, of whom 3 were found to have genomewide representation (GR) profiles reminiscent of cancer-related copy number variation. All 3 were referred for whole-body diffusion-weighted magnetic resonance imaging, which revealed a tumor in each case.

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In Case #1, bilateral ovarian carcinoma with diffuse peritoneal spread was diagnosed. Retroperitoneal lymphadenopathies and presence of bilateral pleural fluid were consistent with ovarian cancer stage-IV-A. Further examination confirmed a high-grade serous ovarian carcinoma that had multiple metastases to the omentum (14 mm), paracolic peritoneum, and the appendix, as well as implants on the small bowel. Of the 30 sampled lymph nodes, 12 tested positive for tumor cells. Fluorescence in situ hybridization (FISH) testing confirmed that the NIPT results were due to tumor-derived cell-free DNA (cfDNA).

In Case #2, a woman who underwent NIPT was found to have multiple supradiaphragmatic and infradiaphragmatic lymphadenopathies as well as diffusion restriction at the spleen and left tonsil, corresponding to Ann Arbor stage III-SE disease. An excision biopsy of the involved tonsil indicated follicular lymphoma grade 3a. Cytogenetic analysis detected an abnormal karyotype in 13 of 20 analyzed cells: 48,XX,i(6)(p10),dup(7)(q11q22),+dup(7)(q11q22),+11,dup(12)(q13q15),dup(13)(q21q34),t(14;18)(q32;q21).

In Case #3, a mass was found in the woman’s anterior mediastinum and multiple lymphadenopathies were seen in the left neck with no involvement in bone marrow, spleen, or visceral organs, corresponding to Ann Arbor stage II disease. Following a transthoracic computed tomography-guided punch biopsy of the mass, a pathological examination indicated a nodular sclerosis form of Hodgkin lymphoma, which was characterized by CD15+/CD30+ neoplastic Hodgkin and Reed-Sternberg cells.

The study authors believe that NIPT is both sensitive and specific for identification of cancer because the number of diagnoses in the prospective cohort was within the range expected for population incidence of the disease and the cfDNA-derived GR profiles were confirmed in biopsy specimens. They urged large-scale research on the efficacy of NIPT for cancer detection in the general population as well as in pregnant women.