Kenya will, in the next two months, introduce an injectable polio vaccine into its routine immunisation programme to contain the on-an-off polio outbreaks reported in the country.
The Salk inactivated poliovirus vaccine (IPV), used in most developed countries, including Canada, contains chemically inactivated poliovirus.
The current oral polio vaccine made from a live poliovirus is given to children in three doses: At two months, four months and the last at between the ages of six and 18 months. But the IPV dose will be given to children from 14 weeks of age.
According to Collins Tabu, an epidemiologist in charge of policy direction on immunisation at the Ministry of Health, the IPV dose will be co-administered with an OPV dose and the other infant vaccines.
“This vaccine will be given at the same time as OPV 3 at the cost of $1 and no extra clinic visit will be required thereafter,” he said. The vaccine is an injectable, 5-dose formulation.
Polio, an acute virus that spreads through faecal matter, can cause paralysis and even death. The disease has been largely eradicated but there are constant outbreaks in Somalia, Kenya, Afghanistan, Pakistan and Nigeria.
The WHO now recommends that countries that have been using only OPV introduce at least one dose of the injectable vaccine into their routine childhood vaccination schedules.
All the developing countries have until the end of this year to introduce IPV into their immunisation programmes. The OPV has been the workhorse of the polio eradication effort since 1988, and because it is cheap and easy to administer, OPV has protected billions of children from paralysis. But the vaccine has a couple of unwelcome features.
Reports indicate that sometimes a child who gets the vaccine will develop polio; that happens in one case per every 2.7 million first doses of OPV given. OPV-vaccinated children also shed viruses in their stool.
“In settings where hygiene is poor, those viruses can spread to other children, immunising them too. But if the vaccine viruses continue to circulate, they can regain the virulence that was engineered out of them in the vaccine manufacturing process and cause paralysis too,” said Dr Tabu.
“To stop those vaccine viruses from spreading, eventually the world will need to cease using OPV.”
In 2016, he said, the WHO will take one component out of the oral vaccine, which protects against three strains of polio, Wild Polio Virus Types 1,2,3.
Dr Tabu said that the Wild Polio virus type 2 has been eradicated globally since 1999, so protection against Type 2 is no longer needed
Given that Type 2 vaccine viruses are still in use in some parts of the world, the plan is to get all countries that use OPV to give each child at least one dose of the more expensive injectable vaccine before the Type 2 component is dropped from OPV. That would ensure all children have some protection against Type 2.
The community of researchers and public health organisations have for years queried the efficacy of OPV in the developing world.
However, the vaccine has had both fierce proponents and steadfast opponents — the latter objecting to its high cost, the need to buy and safely discard mass numbers of syringes and other complications.
A study by scientists from India and from the Global Polio Eradication Initiative looked at the response of previously vaccinated Indian children who received a booster dose of OPV, IPV or a placebo.
The children who received IPV got the best boost to their immune response to the virus. The study provided strong evidence that IPV boosts intestinal immunity among children with a history of multiple OPV doses more effectively than an additional OPV dose.
Polio remains endemic — transmission has never been stopped — in three countries: Pakistan, Afghanistan and Nigeria. And viruses from those countries occasionally reignite spread in neighbouring countries or countries with trade or travel ties.
In May last year, the WHO declared an international public health emergency, citing outbreaks in at least 10 countries. Of particular concern were Syria, Somalia and Iraq, where violence has complicated efforts to contain new cases.
In 2013, 84 per cent of infants around the world (77 per cent in Africa) received three doses of polio vaccine.