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The Expert Group on Serious Adverse Events with History of Human Swine Influenza (HSI) Vaccination today (April 13) published a statement regarding three cases of neurological symptoms and history of HSI vaccination reported to the Centre for Health Protection of the Department of Health. The expert group considers that their illnesses were unlikely to be related to their HSI vaccination.
The first case involved a 70-year-old man presenting with lower limb pain and numbness in late February. He was admitted to Queen Elizabeth Hospital on March 18 and was found to have ataxia after admission. He is now in stable condition.
The man received an HSI vaccination on December 28, 2009, in a public outpatient clinic, about eight weeks before the onset of symptoms.
In the second case, the patient was a 73-year-old woman who presented with numbness of hands and feet on March 4 and followed by weakness of all four limbs.
She was admitted to Kwong Wah Hospital on March 11 and passed away on April 9.
She had received an HSI vaccination on December 31, 2009, in a public outpatient clinic, about nine weeks before the onset of symptoms.
The clinical picture and laboratory investigations of the two patients are compatible with Guillain-Barre Syndrome (GBS), a spokesman for the expert group said.
The third case involved a 65-year-old man who had onset of numbness over the soles of both feet in early March, followed by numbness of fingers of both hands. No hospitalisation was required.
He received an HSI vaccination on December 29, 2009, in a public outpatient clinic, about nine weeks before the onset of symptoms.
A nerve conduction test showed demyelinating polyneuropathy but cerebrospinal fluid showed a normal protein level.
Further monitoring of clinical progression was needed to ascertain the probable diagnosis of this patient, the spokesman said.
"Literature review revealed that the majority of GBS cases that were temporally associated with influenza vaccination occur between the second and the third week.
"On the basis of epidemiological and biological inference, a conservative estimate of the limits of the latencies for GBS is considered to be from five days to six weeks.
"It is more difficult to substantiate a biological association between GBS and an antecedent influenza vaccine administered more than six weeks before onset of symptoms.
"It would be extremely unusual for a large number of GBS cases to cluster at a time point more than six weeks following vaccination," the spokesman said.
In view of the fact that these patients had HSI vaccinations about eight weeks and nine weeks before the onset of symptoms, the expert group was of the view that their illnesses were unlikely to be related to their HSI vaccination.
In Hong Kong, a baseline of about 40-60 GBS cases occur in public hospitals each year.
According to the World Health Organisation, there has been no evidence suggesting a causal relationship between GBS and HSI vaccinations.
The reported number of GBS cases worldwide has been in line with usual background rates prior to the introduction of such vaccines, the spokesman said.
Ends/Tuesday, April 13, 2010
Issued at HKT 19:45
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