ISLAMABAD: As more and more would-be travellers queue up at hospitals and immunisation centres across the country for their dose of the polio vaccine, many have concerns about the vaccine`s safety and the proper dosage for children and adults alike.

Currently, there are two kinds of polio vaccine available, oral poliovirus vaccine (OPV) or polio drops, and the inactivated poliovirus vaccine (IPV), which is administered via intramuscular injection usually a shot in the arm.

According to the World Health Organisation`s Position Paper on Polio Vaccines (February 2014), which lays down the latest international guidelines for immunisation against the disease, WHO no longer recommends OPV-only vaccination. For all countries currently using OPV-only, at least one dose of IPV should be added to the schedule.

This position paper also serves as the background document for a recently issued advisory from the Ministry of National Health Services (MNHS), which is supposed to serve as the guiding document for vaccination in the country.

In polio endemic countries and in countries athigh risk for importation and subsequent spread (such as Pakistan), WHO recommends an OPV birth dose followed by a series of three OPV doses and at least one IPV dose.

Making specific reference to Pakistan, the position paper states: `In Pakistan, a comparison of the serological responses to various OPV or IPV schedules, or combined schedules, confirmed a favourable immunological response to combined IPV+0PV vaccination.

But while WHO maintains that all children worldwide should be fully vaccinated against polio, doctors warn that individuals with certain medical conditions should seek medical advice before being vaccinated.

Contraindications The MNHS advisory takes care to identify cases where OPV is not recommended.

Dr Tabish Hazir, head of paediatrics at the Children`s Hospital of the Pakistan Institute of Medical Sciences (Pims), told Dawn that in certain cases, OPVs were contraindicated. In patients with certain pre-existing conditions that compromise the immune system OPVs can have negative side-effects.

`People who are severely immuno-compromised may be at risk if they are administered liguid pollo drops. The OPV contains a weakened poliovirus which, in rare cases, has been known to cause polio paralysis in individuals with weakened immune systems,` he said.

In addition, people infected with the human immunodeficiency virus (HIV) could also face similar side effects.

`Due to a prevailing social taboo around HIVAids, people usually do not want to disclose thefact that they have the disease. But fortunately, the number of HIV-Aids affected individuals in Pakistan is quite low,` he said. OPV is also not recommended for cancer patients who have been undergoing chemotherapy. Radiation therapy also weakens the immune system, rendering patients more susceptible to even the weakest infections.

`In addition, those prescribed Corticosteroids may be at risk, because steroids can also activate weakened viruses,` Dr Hazir said.

Dr Hazir revealed that patients suffering from Thymus Disorder should not be administered OPVs. The thymus is a specialised organ of the immune system and those afflicted with this disorder tend to get sick quite often.

IPV: A Safe Alternative Dr Tabish said that people with such diseases should be given Inactivated Polio Vaccine (IPV) which is given by intramuscular injection.

`IPV is not a live vaccine as the poliovirus used is deactivated. Therefore, it carries no risk of vaccine-associated polio paralysis. However, IPV is more expensive and needs to be administered by a trained health worker,` he said.

This view is supported by the WHO position paper, which states: `IPV is considered very safe, whether given alone or in combination with other vaccines. There is no proven causal relationship to any adverse events` Dr Mulazim Hussain, director of the polio counter at Pims, told Dawn steps were being taken to inform the public of these precautions.

However, when asked if IPV was available at Pims, he said: `It is very expensive and people who need to be administered IPV should buy it on their own`.