A head to head trial against current poliovirus vaccines finds that a new bivalent oral vaccine against poliovirus types 1 and 3 induces a stronger immune response than the existing trivalent vaccine and a similar immune response to the monovalent vaccine. Furthermore, the new vaccine allows children to be immunised against the two remaining types of wild poliovirus in a single oral dose. These are the conclusions of an Article published Online First in The Lancet.
Mass vaccination with trivalent oral polio vaccine (tOPV) has successfully reduced the number of countries where polio is endemic from over 125 in 1988 to just four today. Despite tOPV targeting all three strains of the virus, and the introduction of monovalent vaccines, transmission of the remaining virus types 1 and 3 persists in parts of the polio-endemic countries of Afghanistan, Pakistan, India, and Nigeria.
The new bivalent type 1 and 3 oral poliovirus vaccine (bOPV) has already been implemented on a large scale in the hope of eliminating transmission of the two remaining virus types. But whether it provides as much immunity as other oral polio vaccines has not been assessed in a rigorous study.
In this study, which was largely funded by The Global Alliance for Vaccines and Immunisation, Roland Stutter from the World Health Organisation, Geneva, Switzerland and colleagues from India examine the protection offered by the new bivalent vaccine compared with monovalent and tOPV vaccines in India.
Between August 2008 and December 2008, 830 newborn babies from three centres in India were randomised to receive either the monovalent, bOPV, or tOPV 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 (rises in antibody levels).
Overall, findings showed that bOPV induced a significantly higher immune response and achieved higher seroconversion rates than tOPV. The bivalent vaccine also showed similar effectiveness to the respective monovalent vaccines.*
All the vaccines were well tolerated. There were 19 serious adverse events, none of which were related to trial interventions.
The authors conclude: "The major advantages of the bivalent vaccine…is that it will enhance individual and population immunity simultaneously for both poliovirus types 1 and 3, without any serious loss in immunogenicity compared with the mOPVs."
In a Comment, Nigel Crawford and Jim Buttery from the Murdoch Children's Research Institute (SAEFVIC), Melbourne, Australia, say that the potential effectiveness of bOPV is already being shown in India where it is being used on a large scale, with polio surveillance figures showing just 32 cases so far this year, compared with 260 in 2009.
However, they point out that the global financial crisis has resulted in a massive funding gap for immunisation programmes worldwide including polio: "The plan of action for polio eradication—with bOPV as the centrepiece—is only 50% funded for 2010".
They add: "Poliomyelitis-free regions of the world need to be reminded of the toll that polio continues to inflict. The potential effect of new vaccine combinations, such as bOPV, is an important step forward. A final concerted effort, both locally and worldwide, is required."
Dr Roland Sutter, World Health Organisation, Geneva, Switzerland. T) +41 22 791 4682 or +41 79 475 5523 (mobile) E) sutterr@who.int
Dr Nigel Crawford, Royal Children's Hospital, Melbourne, Australia. T) +61 393 454 448 E) nigel.crawford@rch.org.au
For full Article and Comment, see: http://press.thelancet.com/polio.pdf
Notes to Editors:
*After one dose of mOPV1 or bOPV, protective antibodies to type 1 poliovirus were developed by 20% of babies compared with 15% given the tOPV. The first dose produced immunity to type 3 virus in 12% of recipients of mOPV3, 7% of bOPV, and 4% of tOPV.
After two doses of mOPV1 or bOPV, approximately 90% of babies developed immunity to type 1 virus, compared with 63% after tOPV. The second dose induced immunity to type 3 virus in 84% of recipients of mOPV3, 74% of bOPV, and 52% of tOPV.
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Journal
The Lancet