A head-to-head trial showed that a new poliovirus bivalent oral vaccine triggers a much stronger immune response compared to existing trivalent ones and could seriously contribute towards total eradication of the disease worldwide, say researchers in the peer-reviewed medical journal The Lancet. The new vaccine protects against types 1 and 3 polioviruses; it also allows children, with just one oral dose, to be immunized against the two remaining types.
There are 3 main strains of poliovirus, they are known as PV1 (poliovirus1), PV2 and PV3, or simply types 1, 2 and 3.
In 1988 polio was endemic in more than 125 countries. The tOPV oral polio vaccine which targets three poliovirus strains, via mass vaccinations brought this number down to just four nations today. Even with the tOPV and monolavent vaccines for the other types 1 and 3 strains, polio is still endemic in Nigeria, India, Pakistan and Afghanistan.
The authors explain that the new vaccine – bOPV – which targets both types 1 and 3 has been implemented on a large scale. bOPV is supposed to eliminated transmission of the remaining virus types. However, only an extensive study would determine whether this has happened.
In this latest study, Roland Stutter and team from the WHO (World Health Organization) assessed the effectiveness and safety of the new bivalent vaccine (bOPV), comparing it with tOPV and monovalent vaccines in India.
830 newborns in three centers in India were randomly selected to receive the monovalent, bOPV, or tOPV vaccines in two doses, and then a booster when 30 days old. The study lasted from August to December 2008. Their blood was tested on three occasions, before any vaccine, after the first one and then after the second one 30 days later. Their aim was to measure rises in levels of antibodies (seroconversion).
They found that bOPV induced a considerably higher immune response than tOPV, as well as achieving much higher seroconversion rates. bOPV also showed similarly better effectiveness when compared to monovalent vaccines; the authors wrote:
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.
The researchers add that all vaccines were well tolerated. The 19 serious adverse events that were reported were in no way related to the vaccines.
The authors concluded:
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.
Nigel Crawford and Jim Buttery from the Murdoch Children’s Research Institute (SAEFVIC), Melbourne, Australia, say that bOPV is being used in India in a large scale with good effectiveness. So far this year only 32 cases of polio have been reported, compared to 260 last year.
They stress that a huge funding gap for immunization programs globally, including polio, could undermine the whole plan. They blame the worldwide financial crisis for this.
They write:
The plan of action for polio eradication – with bOPV as the centrepiece – is only 50% funded for 2010-12.
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 W Sutter MD, Prof T Jacob John FRCP[E], Prof Hemant Jain MD, Prof Sharad Agarkhedkar MD, Prof Padmasini Venkat Ramanan MD, Harish Verma MB, Jagadish Deshpande PhD, Ajit Pal Singh MB h, Meghana Sreevatsava MPH, Pradeep Malankar MD, Anthony Burton, Arani Chatterjee MB, Hamid Jafari MD, R Bruce Aylward MD
The Lancet, Early Online Publication, 26 October 2010
doi:10.1016/S0140-6736(10)61230-5
Written by Christian Nordqvist