POST 01139E : QUESTIONS ON OPV

POST 01139E : QUESTIONS ON OPV Follow-up on Post 01128E 12 August 2007 ____________________________________ This posting contains two contributions in response to André Yaméogo's question. The first comes from Steven_Wassilak of the CDC, and the second is a joint contribution by Hans_Everts and Benjamin_ Nkowane from the Polio Eradication Initiative. Finally Sona_Bari also from PEI takes this opportunity to provide a brief update on progress so far. ____________________________________ Basically, no vaccination opportunity should be missed so don't worry about intervals. Give the trivalent [tOPV] for routine immunization at the usual health facility opportunities. One could consider changing the RI outreach schedule, but again, I would not as it is not worth the risk of missing a child eligible for routine immunization -- there is a good chance that there will not be interference in that child and each additional dose is important towards reaching immunity. In practice, outreach is often curtailed somewhat while vaccination staff prepare for SIAs. Background: OPV campaigns are always 4 or more weeks apart unless they are with the same monovalent, in which case intervals of days have been used. Overall, there is the potential for between-serotype competition for response when intervals are less than 4 weeks (that is, if monovalent type 1 [mOPV1] is followed by tOPV there may be interference with the type 3 response, or if tOPV is followed by mOPV1 there may be interference with the type 1 response to mOPV1 ). Most of the interference between serotypes in tOPV is due to type 2. So, avoiding the limited risk of interference is not worth the more worrisome risk of missing or delaying the routine immunization dose whether before or after the mOPV1 SIA. Steven Wassilak Global Immunization Division, CDC, Atlanta, USA -------------------------- Dear All In response to Dr Yameogo's question on competition of trivalent OPV and monovalent OPV, we have the following comments: Although some interference may occur because of different serotypes would be multiplying in the gut of the child (thereby making one of the doses less effective if interval is too short) the benefits of providing the vaccine regardless of the prior vaccination history of the child far outweigh any risk of interference. OPV provided during SIAs are supplementary and the primary objective is to interrupt circulation of wild virus in the population of children under five. The vaccine also provides additional individual immunity as well as serving as a booster for those already immune. To try and introduce an interval between routine and SIA doses will be a nightmare, with little or no benefit, but a high risk of creating confusion and ending up being counter productive. Some of the issues to consider are: 1. If we stop routine doses during mOPV1 campaigns we compromise population immunity against types 2 and 3 and increase the risk of importations of type 3 or circulating vaccine derived polio viruses (coddv). 2. The 4 weeks interval is a compromise. Some doses given in shorter intervals may be wasted, but many will contribute to population immunity and none will be harmful. In other words, there is nothing to lose, but there is something to gain by not interrupting routine immunization during NID. This is true whether it is monovalent or trivalent. 3. The mothers who come to a Health Centre for vaccination and hear they have to come back a later date for polio, will probably never come back. Interrupting routine during NIDs means adding three necessary visits. This would be disastrous in the countries where polio still is a problem or where there is a risk of spread if there is an importation of a wild poliovirus. 4. Interruption of routine in countries where they do many rounds, would basically mean that OPV is no longer given during routine EPI, or that it would have to be done within a very narrow window of opportunity. Children would therefore be missed, because the mothers would not come in time or because after the rounds they would fall outside of the EPI age group. It would inevitably lead to a drop in coverage. Hans Everts and Benjamin Nkowane Polio Eradication Initiative WHO/Geneva ----------------------------------- One type of poliovirus on the run – eradication efforts get essential injection of cash Wide-scale use of monovalent oral polio vaccine type 1 has significantly curbed transmission of type-1 wild poliovirus. The more virulent and prone to spread of the two remaining poliovirus types, type 1 has caused just three cases this year in the western part of Uttar Pradesh state, India, arguably the most historically entrenched type 1 reservoir in the world. At the same time, no type 1 cases have been reported in Kano, Nigeria, since October 2006 – a noteworthy milestone, given that Kano was the original epicentre of a major international epidemic which re-infected 20 previously polio-free countries across the world from 2003 to 2006. In July, the GAVI Fund Alliance finalized a reprogramming of US$ 104.6 million, to support the current intensified polio eradication efforts. These funds had originally been earmarked for the post-eradication era, and while they do not constitute new funding, they do free up much-needed cash to maintain surveillance and campaign activities through the rest of the year. This and some new contributions have significantly reduced the global funding gap for 2007 to approximately US$ 60 million for the rest of this year. A further US$ 355 million is needed for activities in 2008. In particular, the Global Polio Eradication Initiative is looking to G8 countries to rapidly take action on commitments made at their June Summit in Heiligendamm, Germany. Read the Global Polio Eradication Initiative monthly_ situation_reports ______________________________________________________________________________ All members of the TechNet21 e-Forum are invited to send comments on any posting or to use the forum to raise a new discussion or request technical information in relation to immunization services. 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