そんな子宮頸癌ワクチンに関する話題です。これまで3回の接種が当然と考えられていたHPVワクチンですが、1回の接種での十分に効果があると米国癌学会から紹介がありました。
米国癌学会(AACR)は11月4日、ヒトパピローマウイルス(HPV)ワクチンの1回投与で十分な長期的免疫が得られることを示唆する研究を紹介しています。Cancer Prevention Research誌に掲載されているそうです。
以下のリンクから見ることができます。
http://www.aacr.org/home/public--media/aacr-press-releases.aspx?d=3208
全文を掲載しておきます。
One Dose of HPV Vaccine May Be Enough to Prevent Cervical Cancer
PHILADELPHIA — Women vaccinated with one dose of a human papillomavirus (HPV) vaccine had antibodies against the viruses that remained stable in their blood for four years, suggesting that a single dose of vaccine may be sufficient to generate long-term immune responses and protection against new HPV infections, and ultimately cervical cancer, according to a study published in Cancer Prevention Research, a journal of the American Association for Cancer Research. Mahboobeh Safaeian, Ph.D.
“The latest Morbidity and Mortality Weekly Report from the Centers for Disease Control and Prevention on vaccination coverage indicates that in 2012, only 53.8 percent of girls between 13 and 17 years old initiated HPV vaccination, and only 33.4 percent of them received all three doses,” said Mahboobeh Safaeian, Ph.D., an investigator in the Division of Cancer Epidemiology and Genetics at the National Cancer Institute (NCI) in Bethesda, Md.
“We wanted to evaluate whether two doses, or even one dose, of the HPV 16/18 L1 VLP vaccine [Cervarix] could induce a robust and sustainable response by the immune system,” she added. “We found that both HPV 16 and HPV 18 antibody levels in women who received one dose remained stable four years after vaccination. Our findings challenge previous dogma that protein subunit vaccines require multiple doses to generate long-lived responses.”
Data for this study are from the NCI-funded phase III clinical trial to test the efficacy of Cervarix in women from Costa Rica. About 20 percent of the women in the study received fewer than three doses of the vaccine, not by design.
The researchers looked for the presence of an immune response to the vaccine (measured by antibody levels) in blood samples drawn from 78, 192, and 120 women who received one, two, and three doses of the vaccine, respectively, and compared the results with data from 113 women who did not receive vaccination but had antibodies against the viruses in their blood because they were infected with HPV in the past.
They found that 100 percent of the women in all three groups had antibodies against HPV 16 and 18 in their blood for up to four years. Antibody levels were comparable for women receiving two doses six months apart and those receiving the full three doses.
The researchers also found that while antibody levels among women who received one dose were lower than among those who received the full three doses, the levels appeared stable, suggesting that these are lasting responses. In addition, the levels of antibodies in women from the one- and two-dose groups were five to 24 times higher than the levels of antibodies in women who did not receive vaccination, but had prior HPV infection.
“Our findings suggest promise for simplified vaccine administration schedules that might be cheaper, simpler, and more likely to be implemented around the world,” said Safaeian. “Vaccination with two doses, or even one dose, could simplify the logistics and reduce the cost of vaccination, which could be especially important in the developing world, where more than 85 percent of cervical cancers occur, and where cervical cancer is one of the most common causes of cancer-related deaths.”
In some parts of the world, including Chile and British Columbia, two doses of HPV vaccine is now the recommended vaccination program, according to Safaeian. But for a single HPV dose, “while our findings are quite intriguing and show promise, additional data are needed before policy guidelines can be changed,” she clarified. “For instance, it is important to note that persistence of antibody responses after a single dose has not been evaluated for Gardasil, the quadrivalent HPV vaccine that is more widely used in the United States and many other countries.”
This clinical trial was sponsored by the NCI with support from the National Institutes of Health Office of Research on Women’s Health and the Ministry of Health of Costa Rica. The HPV vaccine was provided by GlaxoSmithKline Biologicals. Safaeian declared she has no conflicts of interest.
英語が苦手な方のために日本語で要約しておきます。
この研究は、米国立癌研究所(NCI)によるHPV16/18 L1 VLPワクチン(商品名サーバリックス)の有効性に関する第3相臨床試験のデータを使用しています。ワクチン投与を受けた被験者女性(1回投与78人、2回投与192人、3回投与120人)の血中抗体レベルを調べ、ワクチン未投与だが過去の感染により抗体を持つ女性113人と比較したものです。
ワクチン投与を受けた被験者は、HPV16および18に対する抗体を、回数にかかわらず全員が最高4年間保持していました。また、1回投与を受けた女性の抗体レベルは、投与完了者(3回投与)よりも低いとはいえ安定しており、長期的な免疫応答が得られていることが分かりました。1回および2回投与群の抗体レベルは、ワクチン未投与のHPV感染経験者より5-24倍高かくなっていました。
｢このような結果を得たことから、HPVワクチンの投与スケジュールを簡素化できる可能性があります。ただし、米国その他で使用頻度の高いガーダシルについては調査しておらず、ガイドライン書き換えにはさらにデータが必要です」と、研究者は述べています。
以下は私のコメントです。
HPVワクチンですが、1回の接種での十分に効果があるのであれば、費用の面でも時間の面でも大きな利益があるわけで、3回接種から1回接種に移行しても良いかと思われます。もちろん接種回数が減ることで副作用のリスクも必然的に減ることになります。この研究成果には大きく期待したいところです。
HPVワクチンにはサーバリックスとガーダシルがあるわけですが、早急にガーダシルでの研究も望まれます。
にほんブログ村