For World Immunisation Week 2015 we highlight how MRC Unit The Gambia is contributing to the global fight to eradicate polio, assessing the timing of the injectable, inactivated polio vaccine (IPV) within immunisation schedules, and evaluating the impact of IPV introduction in The Gambia.
Eradicating polio remains an urgent global public health priority.  There are now only a few hundred cases of polio recorded in the world each year in a small number of countries, and with ongoing international efforts, eradication is in sight.

As part of the strategy to eradicate polio globally, the http://www.polioeradication.org/Resourcelibrary/Strategyandwork.aspx calls for introduction of at least one dose of IPV into all country immunisation programs by the end of 2015, in addition to the oral polio vaccine drops currently in use. On 1 April, the Ministry of Health and Social Welfare through the Expanded Programme on Immunisation (EPI) introduced the IPV in The Gambia for the prevention of polio.

Examining the safety and efficacy of IPV timing

In 2013, Dr Ed Clarke, Head of Infant Immunology and Professor Beate Kampmann, Theme Leader for Vaccines and Immunity at MRC Unit The Gambia, were awarded a substantial grant by the Bill and Melinda Gates Foundation to undertake a clinical trial to examine vaccine interference between IPV and other vaccines (measles and rubella combined vaccine and yellow fever vaccine) given to infants in The Gambia, according to the WHO EPI vaccine schedule.

The purpose of the study was to assess if there was any interference between IPV and other vaccines given at the same time, as this is important information when any new vaccine is added to the existing schedule. The study also aimed to compare the immunogenicity and safety of IPV when administered via different routes and using novel immunisation devices.  A large team of nearly 100 people recruited 1,504 nine- and 10-month-old infants in just over six months, to ensure the important data needed was available for future decisions by the WHO. The IPV team is working closely with the Ministry of Health and Social Welfare, the EPI officer of the Government of The Gambia and the regional health team. The study is now completed and results are currently being submitted for publication.

New study to assess vaccine impact Dr Olubukola Idoko, Clinical Trial Coordinator and Paediatrician at MRC Unit The Gambia, has recently secured funding from the Centres for Disease Control (CDC) Atlanta and WHO, for a new study to assess the impact of IPV introduction in The Gambia on healthcare workers and families. The study is being conducted under The Unit’s Vaccines and Immunity theme in collaboration with the Gambian EPI and regional health teams.

Since a dose of IPV is now being introduced at four months of age, an additional injection will be received by each infant. Three injections, instead of the current two, at the same EPI visit is already practice in many countries that give pentavalent (containing diphtheria, pertusiss, tetanus, haemophilus influenza type b and hepatitis b vaccine antigens) and pneumococcal conjugate vaccine injections.

Although safe and immunogenic, there are concerns that the offer of three or more injections at a single EPI visit could affect acceptance and subsequently vaccination coverage. Good understanding of the need of the IPV dose, and addressing perceptions – particularly among healthcare providers' (HCPs) and infant caregivers offering vaccinations – are important to mitigate against such concerns.

In collaboration with Dr Martin Ota of the WHO African regional office (former immunologist at MRC Unit The Gambia), the investigators wish to understand possible factors which determine vaccine acceptance, and any potential effects on vaccine uptake. The questionnaire-based study is a cross-sectional survey among HCPs and caregivers at EPI clinics in rural and urban Gambia.

The nationwide survey of representative health centres started in March 2015 and the first arm, led by Dr Robert Mboizi, was already completed before introduction of the IPV into the national immunisation schedule in The Gambia on 1 April. The same facilities will be sampled post-introduction, in the next few months.

The findings of the study may inform vaccine policy makers in The Gambia and in other countries who are trying to determine which immunisation schedules best balance vaccine effectiveness, ease of administration, and concerns about acceptance of the administration of multiple injectable vaccines at a single visit.

The study is part of a larger group of studies initiated by WHO and the CDC to address the acceptability questions associated with introduction of IPV into the EPI schedule and will inform WHO directly. The study findings may also inform the content of training packages for health care personnel that could be used in future vaccine introductions in The Gambia and other countries.

“This important survey will give us useful insight into the acceptability of multiple injections at the same vaccination visit among caregivers and healthcare professionals,” said Dr Olubukola Idoko.

“This is crucial now, as more vaccines find their way into our routine immunisation schedules, especially as polyvalent preparations – which can combine several vaccines in the same shot – are not always an option. Also key will be our ability to compare our findings with those from other WHO regions. Our findings have a potential to impact on policy, health care provider training and immunisation messages in general.”

Read more about http://www.polioeradication.org/Resourcelibrary/Strategyandwork.aspx at The Unit.

 MRC Unit The Gambia is hosting the 3rd International Neonatal & Maternal Immunisation Symposium (INMIS) ‘Global Strategies for Global Impact’ from 4-6 November 2015. Find out http://www.polioeradication.org/Resourcelibrary/Strategyandwork.aspx..