PETALING JAYA (Nov 29, 2009): Only a few cases of Guillain-Barre (G-B) syndrome were reported throughout the world following vaccination with the H1N1 vaccine.

"To date, less than a dozen suspected cases of G-B have been reported after vaccination and only a few of these cases may be linked to the pandemic vaccine," the World Health Organisation (WHO) said on Thursday.

Speaking at the weekly H1N1 Pandemic 2009 briefing from Geneva, Dr Marie-Paule Kieny, director, Initiative for Vaccine Research, said the reported G-B cases were transient (momentary) and all the patients have recovered.

Kieny said there has been particular concern about G-B syndrome because of the similar incidences where the condition spiked among the American population during the swine flu vaccination campaigns in 1976.

On fatalities following vaccine administration, Kieny said deaths reported to the WHO have been investigated by national health authorities in the countries where they have occurred.

"Although investigations are still on-going, results of the completed investigations have ruled out the H1N1 vaccine as the cause of the fatalities," said Kieny.

She said at least 80 million doses of vaccine have been distributed and that at least 65 million doses have already been administered.

"These are figures that we have received from 16 countries, but we think they are conservative estimates because immunisation campaigns are under way now in 40 countries," said Kieny.

She said, considering this mammoth scale of vaccine administration, at least some rare adverse events could not be "excluded".

"But from what we see so far, the pandemic flu vaccine has the same safety profile as the seasonal flu vaccine."

She said surveillance systems have been set up to record any occurrence of illness or death in people who have been vaccinated.

"So far, there have been a similar number of events reported as we would see for seasonal flu vaccine.

"We have seen a rate of about one report for 10,000 doses of vaccine. Only five reports out of 100 are for a serious event," said Kieny.

"Since many deaths and illnesses are expected in the general population over any given period of time from other causes, the investigations focus on finding if there is a plausible link to the vaccine. The reports are then assessed to see if the vaccine may be the cause."

What is Guillain-Barre syndrome?

ACCORDING to the Merck Manual of Medical Information, the Guillain-Barre (G-B) syndrome is a neurological disorder, usually occurring weeks after a viral infection, a sore throat, bronchitis, influenza attack, surgical procedure – or after undergoing vaccination.

The acute form of G-B syndrome can worsen rapidly and is a medical emergency.

Symmetric weakness of the limbs develops over a few days, beginning in the legs, and sometimes progressing to complete paralysis.

The face muscles may be paralysed as well, making it impossible to swallow.

In severe cases, paralysis of respiratory muscles require artificial ventilation on a respirator.

With intensive medical treatment and support, the majority of patients recover, but about 10 to 20% are left with some residual weakness.

The illness results from inflammation and destruction of myelin (the fatty material, composed of lipid and protein that forms a protective sheath around some types of nerve tissue) similar to that seen in multiple sclerosis.

The main difference, however, is that multiple sclerosis attacks the central nervous system, whereas in G-B, it is the peripheral nerves that are affected.

The nerve damage is thought to be the result of an abnormal immune reaction directed against the myelin of the peripheral nervous system.