Đặng Đức Anh, director general of the Viet Nam National Institute of Hygiene and Epidemiology, spoke to the Vietnam News Agency on the safety of changes in the polio vaccine regime for infants.

Is poliomyelitis, or polio, a common disease among Vietnamese children?

Poliomyelitis - commonly known as polio - is an acute and communicable disease caused by the polio virus. Following the virus entering a child’s body, it can attack his or her central nervous system and can cause damage to the child’s motor nerve cells. As a consequence, in serious cases the child may die or become partially paralyzed and be unable to walk normally.

Polio is a communicable disease and if the percentage of children vaccinated within a community is low it can lead to an outbreak.

Before 2000, polio was among the leading killers of Vietnamese children, particularly those under the age of five. In recognition of the country’s efforts, the World Health Organisation declared that Viet Nam had eliminated polio in 2000.

In the past 15 years, in addition to the campaign to give three doses of trivalent oral polio vaccine (tOPV) to children in the age groups of two, three and four months, plus supplementary drives to give vaccines to children living in high risk zones, we can say that polio has been successfully eradicated from Viet Nam.

Based on what you have mentioned above, polio has been eradicated. So why do children still have to take an oral polio vaccine?

The wild polio virus still circulates in a number of countries and the movement of people in the world nowadays has been increasing rapidly. Given this, we still have to take preventative measures.

The tOPV vaccine (containing weakened strains of type 1, 2 and 3 polio viruses) has been given to children in the age groups from two to four months old for more than half a century in many countries all over the world. This vaccine has been confirmed safe and highly effective. Another type of vaccine – bivalent oral polio vaccine or bOPV – that contains only polio virus types 1 and 3 has recently been introduced in many countries to replace tOPV.

However, a new injection polio vaccine (IPV) containing polio virus types 1, 2 and 3 has been used in the expanded program of immunization (EPI) in many countries. The Viet Nam EPI also plans to introduce the IPV vaccine in 2018.

Will you please explain why other countries have chosen to switch from the tOPV (3 type) to bOPV (2 type) vaccine? Are there safety concerns with tOPV?

I should say that tOPV vaccines are a form of live vaccine. It contains a weak, yet living form of the polio virus. There is always a possibility that the weak form could mutate into a new form that could challenge the community. According to researchers, the chance of this occurring is very small, but still we have to take precautions, particularly with the type 2 virus.

The tOPV vaccine containing three strains of polio have been widely used across the world for dozens of years and have proven very effective in efforts to eliminate polio among children. In September last year, the WHO announced the elimination of the wild polio virus type 2 worldwide. That’s why if we continue to use the vaccine that contains the type 2 virus, the effects might not be as good as expected.

Some unwanted results of the 3-type polio vaccine were reported in a few countries in 2012. That’s why, to reach the target of eradicating polio worldwide, the WHO has asked all countries to replace the three-type polio vaccine (tOPV) with the two-type (bOPV) in their EPI programmes from May 2016.

Will you please elaborate on Viet Nam’s plan to use the next polio vaccine that has been recommended by the WHO?

The WHO has recommended that all countries using tOPV vaccines switch to bOPV as from May 2016. I can say that all countries have implemented the WHO recommendations, including Viet Nam. According to plan, Viet Nam will start using bOPV in June 2016.

As from May 2016, Viet Nam stopped giving tOPV to children in the EPI national programme, and as from June, bOPV will be given to all children covered by the EPI programme.

Those children who are in the process of taking tOPV can switch to bOPV without having to start the programme again without any consequence to their health.

I want to reiterate that both types of vaccine, tOPV and bOPV, are safe and effective for children.

The immunization schedule for bOPV is the same as that for tOPV. The first dose for a child is at the age of two months, the second dose is at three months; and the final dose is at four months of age. — VNS