3つのタイプ1,2,3 により引き起こされるが、タイプ2 は1999年のインドでの発症が最後であるので、他の2タイプを撲滅のターゲットとしている。
25 October 2010 Last updated at 23:20 GMT
New polio vaccine more effective in reducing disease
By Ania Lichtarowicz Health reporter, BBC News
A new vaccine against the polio virus has helped reduce the number of cases by more than 90%.
Research published online in the journal The Lancet, shows that the new vaccine is significantly better at protecting children against polio than the current popular vaccine.
It has already been used in Afghanistan, India and Nigeria.
The scientists behind the work believe this new vaccine could help to finally eradicate the disease.
Mass vaccination campaigns have led to the number of polio endemic countries falling from 125 in 1988 to just four in 2005.
This meant an actual drop in cases from 350,000 to just 1,606 in 2009.
Polio is caused by one of 3 versions of the polivirus: type1, type 2 or type 3.
Until recently, vaccines targetting either all three forms of the virus or just one of them were used to immunisie children.
The last case of type 2 polio was recorded in India in 1999, so it's the other two types that need to be targeted to finally eliminate the disease.
The authors of the study carried out a trial in India comparing the commonly used old vaccines to the new one, which is taken orally.
In total, 830 newborn babies received either the new vaccine or one of the old vaccines in two doses - one at birth and one 30 days later.
Blood samples were taken before vaccination and after the first and second doses to measure seroconversion - the rise in antibodies produced by the immune system against polio.
It appears that the new vaccine is about 30% more effective in protecting against polio than the most commonly used vaccine to date.
The new vaccine has already been used in immunisation campaigns in Afghanistan, India and Nigeria.
In India the number of cases this time last year was 464. Over the same period this year there have only been only 39 cases.
Nigeria has seen an even greater difference, with cases falling by 95%.
The new vaccine and improved immunisation programmes appear to be responsible for this significant decrease, according to the World Health Organization (WHO).
Dr Roland Sutter, from the WHO and the lead author of the study, told BBC News: "This (new) vaccine could get us over the top and get us to the finish line for eradication.
"The dramatic drop in the number of polio cases in India and Nigeria is attributable to the new vaccine and better coverage during immunization campaigns."
The private sector manufacturers played a key role in its development, says Dr Bruce Aylward, the Director of WHO's Global Polio Eradication Initiative.
"They've held the price to the same price of what we are paying for the older polio vaccine," he says.
The new vaccine can be administered in the same way as the previous one. "That's why there is so much promise with this product," says Dr Aylward.
Commenting on the research, Nigel Crawford and Jim Buttery from the Murdoch Children's Research Institute (SAEFVIC) in Melbourne, Australia, said that the new vaccine had shown great promise.
However they cautioned that the global financial crisis had resulted in a massive funding gap for immunisation programmes worldwide, including polio.
The Lancet, Early Online Publication, 26 October 2010
doi:10.1016/S0140-6736(10)61230-5Cite or Link Using DOI
Immunogenicity of bivalent types 1 and 3 oral poliovirus vaccine: a randomised, double-blind, controlled trial
Dr Roland W Sutter MD a Corresponding AuthorEmail Address, Prof T Jacob John FRCP[E] b, Prof Hemant Jain MD c, Prof Sharad Agarkhedkar MD d, Prof Padmasini Venkat Ramanan MD e, Harish Verma MB f, Jagadish Deshpande PhD g, Ajit Pal Singh MB h, Meghana Sreevatsava MPH a, Pradeep Malankar MD a, Anthony Burton a, Arani Chatterjee MB h, Hamid Jafari MD f, R Bruce Aylward MD a
Poliovirus types 1 and 3 co-circulate in poliomyelitis-endemic countries. We aimed to assess the immunogenicity of a novel bivalent types 1 and 3 oral poliovirus vaccine (bOPV).
We did a randomised, double-blind, controlled trial to assess the superiority of monovalent type 2 OPV (mOPV2), mOPV3, or bOPV over trivalent OPV (tOPV), and the non-inferiority of bivalent vaccine compared with mOPV1 and mOPV3. The study was done at three centres in India between Aug 6, 2008, and Dec 26, 2008. Random allocation was done by permuted blocks of ten. The primary outcome was seroconversion after one monovalent or bivalent vaccine dose compared with a dose of trivalent vaccine at birth. The secondary endpoints were seroconversion after two vaccine doses compared with after two trivalent vaccine doses and cumulative two-dose seroconversion. Parents or guardians and study investigators were masked to treatment allocation. Because of multiple comparisons, we defined p?0?01 as statistically significant. This trial is registered with Current Controlled Trials, ISRCTN 64725429.
900 newborn babies were randomly assigned to one of five vaccine groups (about 180 patients per group); of these 70 (8%) discontinued, leaving 830 (92%) for analysis. After the first dose, seroconversion to poliovirus type 1 was 20% for both mOPV1 (33 of 168) and bOPV (32 of 159) compared with 15% for tOPV (25 of 168; p>0?01), to poliovirus type 2 was 21% (35 of 170) for mOPV2 compared with 25% (42 of 168) for tOPV (p>0?01), and to poliovirus type 3 was 12% (20 of 165) for mOPV3 and 7% (11 of 159) for bOPV compared with 4% (7 of 168) for tOPV (mOPV3 vs tOPV p=0?01; bOPV vs tOPV; p>0?01). Cumulative two-dose seroconversion to poliovirus type 1 was 90% (151 of 168) for mOPV1 and 86% (136 of 159) for bOPV compared with 63% (106 of 168) for tOPV (p<0?0001), to poliovirus type 2 was 90% (153 of 170) for mOPV2 compared with 91% (153 of 168) for tOPV (p>0?01), and to poliovirus type 3 was 84% (138 of 165) for mOPV3 and 74% (117 of 159) for bOPV compared with 52% (87 of 168) for tOPV (p<0?0001). The vaccines were well tolerated. 19 serious adverse events occurred, including one death; however, these events were not attributed to the trial interventions.
The findings show the superiority of bOPV compared with tOPV, and the non-inferiority of bOPV compared with mOPV1 and mOPV3.
GAVI Alliance, World Health Organization, and Panacea Biotec.
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