The success of the global effort to eradicate polio may rest on the outcome of a week-long tour of India, South Africa and Indonesia by a Nigerian delegation which has been conducting tests on polio vaccines used for immunisation in Nigeria.
The team, which was due to return home on Thursday, comprised health officials nominated by the government and Jama'atu Nasril Islam, an umbrella group of Muslim organisations in Nigeria, and key Muslim leaders.
The federal government is hoping this high-powered delegation will these polio vaccines the all clear. That would help to dispel widespread suspicion in the mainly Muslim north of Nigeria that the vaccines contain anti-fertility agents and the virus that causes AIDS.
Many Muslims in the north believe that polio vaccination is being used as a ploy by Western countries to inject people with certain chemicals to reduce their fertility or infect them with HIV/AIDS in order to reduce the population of Muslims.
"We put together a team that incorporates all the stakeholders so that they will see for themselves and be convinced whether or not the polio vaccine is safe," Nigeria's Minister of Health Eyitayo Lambo told reporters in Abuja as the team departed last week.
He predicted that the team would return with good news in time for the next round of nationwide polio immunisation due between 23 and 26 February.
In October 2003 the governors of three states in northern Nigeria - Kano, Kaduna and Zamfara -decided to suspend polio immunisation until the vaccines were investigated and proven safe.
They gave in to rumours and suspicions going back several years which had culminated in the widespread rejection of polio vaccination by people in the north.
The word that polio vaccines were contaminated was first spread by some Islamic preachers.
Their claims assumed greater credibility when they were taken up by the self-proclaimed Supreme Council for Shari'ah in Nigeria (SCSN), an organisation led by physician and one-time presidential aspirant Datti Ahmed.
Following the suspension of polio vaccination by the three northern states, President Olusegun Obasanjo's federal government ordered that tests be conducted on the vaccines to determine their safety.
Kano, Kaduna and Zamfara states also ordered their own separate investigations.
Tests conducted at the National Hospital Abuja and at a laboratory in South Africa at the behest of the federal government showed the vaccines to be uncontaminated by any of the suspected chemical and biological agents.
However Kano state government said its own tests showed the vaccines contained levels of the hormone oestrogen capable of lowering fertility in women.
Neither Zamfara nor Kaduna states have made known the results of their own probes. Neither have they lifted their suspension of polio vaccination.
In the meantime, polio, which had been eradicated in almost all of Nigeria with the exception of Kano state - the last known reservoir - has made a comeback. Not only in Nigeria, but also in several neighbouring countries where it had previously been wiped out.
According to the World Health Organisation (WHO), strains of the virus traceable to Kano state, have recently been traced to other parts of Nigeria, including the nation's commercial capital Lagos.
WHO reported that more than 40 percent of the 677 new cases of polio recorded worldwide last year were in Nigeria.
Recently Nigerian strains of the polio virus have appeared in several west and central African countries, including Benin, Togo, Ghana, Burkina Faso, Cameroon and Central African Republic.
This has raised concern among international health experts that the world might be slipping in its efforts to wipe out polio by 2005.
In January WHO convened an urgent meeting of health ministers from the main countries where polio is endemic to devise strategies to ensure that the disease is in fact eliminated from the globe by the end of next year. Those who attended the Geneva meeting included Nigeria, India, Pakistan, Afghanistan, Egypt and Niger.
Lambo pledged to the other delegates that the federal government would ensure that all Nigerian children were immunised against polio this year.
Since his return, the Nigerian health minister has held meetings with Muslim leaders and the authorities of the three states that suspended immunisation to try to restore nationwide confidence in polio vaccination.
This round of consultations led to the decision to send out a delegation containing representatives of both sides of the divide in the controversy to conduct new tests abroad.
However, SCSN leaders have warned that they will not necessarily accept the delegation's findings, dashing hopes that a positive report from its members might finally settle the argument.
Accusing Obasanjo's government of insincerity on the matter, SCSN secretary general Nasiu Baba-Ahmed, told reporters on Tuesday that his group "will not accept whatever result" the delegation brings back.
Baba-Ahmed said the government had "hired some traditional rulers as members of the team" who lacked the scientific knowledge to tell if the vaccines were contaminated.
Some analysts acknowledge there have been incidents in the past which may have given rise to legitimate suspicions about government-sponsored vaccination campaigns.
But they also point out that the immunisation as a whole has been politicised by certain forces in northern Nigeria that hope to boost their public support by rejecting the polio vaccine.
The fiasco arising from trials of a new meningitis drug by US pharmaceuticals giant Pfizer in Kano in 1996 is often cited as a legitimate reason for northerners to beware of the polio vaccine.
Hundreds of victims of a meningitis epidemic, most of them children, were treated that year with a new Pfizer drug. Many parents complained later that they had not been told their children were being used as human guinea pigs to test a new drug which had severe side effects and was not always successful.
Several children who were administered the trial drug still died of meningitis. The parents of many of those who survived meanwhile claimed that their children had suffered side effects, including loss of speech and deafness as a consequence of the treatment.
The victims are currently pursuing a class action suit against Pfizer in the US courts.
"A deep suspicion of any mass application of Western medicine has continued to linger in northern Nigeria since then," Dauda Abubakar, a Kano-based pharmacist, told IRIN.
"This feeling has only intensified following events such as the September 11 attacks and the US invasion of Iraq and Afghanistan," he added.
According to Abubakar, some radical Islamic groups see opposition to polio vaccination as a means of expressing their anti-Western feelings. The best known of these organisations is the SCSN.
Apart from opposing polio vaccination, SCSN has also launched a campaign against the implementation of some United Nations conventions in Nigerian on the grounds that they are offensive to Islam.
These include the Convention Against Cruel, Inhuman and other Degrading Treatment or Punishment, the Convention on the Elimination of All Forms of Discrimination Against Women and the Convention Against Child Abuse.
Over the past five years 12 states in northern Nigeria states have adopted strict Islamic or Shari'ah law stipulating punishments including stoning to death for adultery, amputation of limbs for stealing and public flogging for drinking of alcohol and pre-marital sex.
The SCSN believes that implementing these UN conventions in Nigeria would undermine the application of strict Islamic law.
Ahmed, the leader of the SCSN, told IRIN his opposition to immunisation was limited to polio and did not extend to vaccination against other preventable diseases.
"As a medical practitioner I'm aware of the value of vaccination but my worry is about polio," he said.
Ahmed said suspicions about the vaccine did not originate in Nigeria and that he had obtained information suggesting the polio vaccine contained unwholesome contaminants from the internet.
"All we want is that we should be given vaccines that are not contaminated for our people," he said.
It remains to be seen how the authorities in Kano, Kaduna and Zamfara states will receive the results from the latest laboratory investigation of the polio vaccine and what impact the findings will have on efforts to wipe out the virus.
Polio has already crippled thousands of children in Nigeria.
While many among the ordinary people in northern Nigeria remain wary of the vaccine, there are still some who are willing to have their children immunised.
"I heard about the controversy but my husband agreed that we still give our baby the polio vaccine," Amina Abdulkadir, a 28-year-old mother in Kano city told IRIN.
She said that she and her husband had seen the effects of polio on other children and did not want their own to suffer the same fate.
But 32-year-old Aishatu Mohammed took a different line. "We will receive the other vaccines, but not the oral polio vaccine because they said it contains harmful substances," she said. "Besides with or without the vaccine, Allah protects his own."