Dr Mbambole Grace Alake, Sub-Director for Immunisation, Directorate of Family Health, Ministry of Public Health, talks on the recent directive that all adult travellers to and from Cameroon must henceforth receive the polio vaccine.

A recent release by the Minister of Public Health calls on persons of all ages to get vaccinated against poliomyelitis before any journey out of the country. What justifies this measure?

On May 5, 2014, the Director-General of the World Health Organisation declared the international spread of wild poliovirus (WPV) a public health emergency of international concern (PHEIC). The declaration followed advice given by an Emergency Committee under the International Health Regulations (IHR) that was convened to assess whether the international spread of polio in 2014 during what is normally the ‘low’ season for poliovirus transmission is a PHEIC and what temporary recommendations should be considered to reduce the risk of international spread.

Currently, ten countries have active WPV transmission that could spread to other countries through population movements. From January to April 2014, WPV has spread internationally in central Asia (from Pakistan to Afghanistan); in the Middle East (from Syria to Iraq); and, in central Africa (from Cameroon to Equatorial Guinea). Temporary recommendations under the IHR (2005) say States currently exporting the wild poliovirus should officially declare, if not already done, at the level of head of State or government, that the interruption of poliovirus transmission is a national public health emergency.

They should also ensure that all residents and long-term visitors, that is for more than four weeks, should receive a dose of oral polio vaccine (OPV) or inactivated poliovirus vaccine (IPV) between 4 weeks and 12 months prior to international travel. Furthermore, the States should ensure that persons undertaking urgent travel, that is within four weeks, and who have not received a dose of OPV or IPV in the previous four weeks to 12 months, receive a dose of polio vaccine at least by the time of departure as this will still provide benefit, particularly for frequent travellers. Lastly, such travellers should be provided with an International Certificate of Vaccination to record their polio vaccination and serve as proof of vaccination.

Will the recommended dose of vaccine be sufficient to eliminate risks of contamination?

One dose of OPV produces immunity to all three poliovirus serotypes in approximately 50 per cent of recipients. Three doses produce immunity in more than 95 per cent of recipients. Immunity is long-lasting and probably life-long.

Why involve all travellers?

Most people infected with poliovirus have no signs of illness and are never aware they have been infected. These symptomless people carry the virus in their intestines and can “silently” spread the infection to thousands of others before the first case of polio paralysis emerges.

Why have ongoing immunisation campaigns against poliomyelitis been targeting essentially children aged between zero and five years?

This is because young children who are not yet toilet-trained are a ready source of transmission, regardless of their environment