How swine flu confounded all expectations

PUBLISHED : Monday, 08 March, 2010, 12:00am
UPDATED : Monday, 08 March, 2010, 12:00am

With the same 'HSI' abbreviation, the human swine influenza and Hang Seng Index have at least one other thing in common - their unpredictability.

Financial analysts find it hard to predict the perturbations of the stock market, and doctors and health offi-cials face the same problem with the flu.

Health officials long predicted a second wave of human swine flu this winter and initiated a vaccination programme for two million 'high-risk' people. But no second wave appeared.

The H1N1 2009 virus, as the World Health Organisation refers to it, surfaced in Mexico in March last year. After outbreaks in North America in April, the new virus spread rapidly around the world. The WHO declared a pandemic in June after 74 countries and territories had report-ed cases. But a year on, swine flu ac-tivity in many countries is waning.

The WHO's emergency committee last month noted as much and said it needed more time and information to assess swine flu globally.

By February 28, more than 213 countries had reported laboratory-confirmed cases of pandemic influ-enza H1N1 2009, and at least 16,455 deaths attributable to the virus.

In Hong Kong, as of March 3, 256 severe infections of human swine flu had been recorded, resulting in the deaths of 73 people aged one to 95. More than 40 swine flu victims are under hospital care at present. Health officials say the incidence of swine flu in Hong Kong has contin-ued to decrease since a peak in September and October. During the week of February 21-27, 8.5 per cent of patients attending government flu clinics tested positive for the H1N1 virus, compared with more than 70 per cent in September.

During the same week in February, 55.1 of every 1,000 people who visited general practitioners had flu-like symptoms, a slight increase on the previous week. But influenza B virus, not swine flu, has emerged as the most prevalent recent strain.

Not surprisingly, public response to the swine flu vaccination programme - the biggest of its kind in Hong Kong - has fallen short of gov-ernment expectations.

Since it began in December, only about 9 per cent - 181,636 - of the two million people in 'high risk' groups have had the shots.

The programme covers five high-risk groups - elderly people aged over 65, children aged between six months and six years, pregnant women, health-care workers, chroni-cally ill patients and poultry workers.

But after several people experi-enced adverse reactions to the shots, the number of people seeking vaccinations dropped from more than 10,000 a day at the peak to about 500 a day now.

Cheung Tak-hai, vice-chairman of the Alliance of Patients' Mutual Help Organisations, said many chronically ill patients had been scared off by the news of a suspected incident of Guillain-Barre syndrome which was linked to the vaccinations, and that several pregnant women who had had vaccinations, had suf-fered miscarriages. A government health committee later said neither the Guillain-Barre syndrome case, nor the miscarriages were caused by the vaccinations.

Guillain-Barre syndrome is a se-vere disorder of the nervous system causing muscle weakness and even paralysis. Incidents of the syndrome, linked to flu vaccinations, have occurred in other countries.

Cheung, a heart patient, did not get vaccinated. 'Many people do not want to take the risk, especially when swine flu is getting very mild,' he said. 'Some of my friends have advised me not to rush for a shot. I will wait and see. But we appreciate the govern-ment's push get vaccine supplies for Hong Kong people, given that swine flu could become very virulent.'

The poor public response has put the government in an embarrassing situation - money has been spent but vaccination targets have not been met. The government bought three million doses of swine flu vaccine late last year from French drug maker Sanofi Pasteur at HK$79 each. It now has more than two million doses of the vaccine left on the shelf, which will pass their use-by dates at the end of the year.

The WHO said that the H1N1 flu virus would be only one of three strains covered by the next flu vaccine manufactured for the Northern hemisphere.

Undersecretary for Food and Health Professor Gabriel Leung, an epidemiologist, said the latest evi-dence indicated that the chance of human swine flu triggering a winter flu peak in Hong Kong this year 'is not high'. He said that was because both elderly people and the student population in the city already had a high immunity to the disease.

'The pathogenicity [the ability of a pathogen to produce an infectious disease] of this virus is not as bad as we feared ... we are very lucky,' he said. 'Elderly people seem to have a pre-existing immunity because those born before 1957 experienced the last [H1N1] pandemic. Their cross-protection against various kinds of flu virus [accrued] over the years has also given them some protection.'

A University of Hong Kong study also had surprising results. It showed that about half of Hong Kong's pri-mary and secondary students had antibodies to the new H1N1 virus.

'This age group is a high transmission group,' Leung said. 'With such a high percentage of students protected, it is difficult for the virus to spread among this group and break out of it.'

But the government would not declare Hong Kong safe from the threat of human swine flu, which had disrupted the normal 'flu rhythm'.

Hong Kong used to have two flu peaks - a summer peak around July and August, and a winter peak in Feb-ruary and March. But the advent of human swine flu delayed the summer peak till September and October, and a winter peak did not happen.

Leung said a second wave of swine flu may emerge in the summer before the incidence of flu got back to its normal 'rhythm'. 'What will happen next we don't know for sure,' he said. 'You can't look at swine flu with conventional wisdom.'

Asked about the government's recent ultimately incorrect swine flu forecast, Leung said any assessment depended on information available at the time. 'It is easy to comment in hindsight,' he said. 'The principle the government has used is to plan for the worst and hope for the best.'

Previous pandemics have amply illustrated flu's unpredictability. According to the WHO, the 1918 flu pandemic, which killed an estimated 50 million people, began as a mild disease but returned within six months in a much more lethal form.

The 1967 pandemic behaved sim-ilarly although it was much less lethal than the one in 1918. A 1968 flu pandemic began as a relatively mild disease and stayed that way during a second wave in many countries.

Leung said that the HKU study findings and other analysis had not been available until last month but had allowed for a much more accu-rate flu assessment.

'When we purchased the vaccines, we did not know if swine flu would have an explosive outbreak or a slow burn, or if it would come in two waves, or three or four waves,' he said. 'That's why we keep saying (vaccination) is a precautionary measure.'

After the swine flu virus hit Hong Kong in May, the government used various containment and mitigation measures, including, in the early stages of the disease's onset in Hong Kong, the quarantining of 300 guests and staff at Metropark hotel in Wan Chai and a group of schoolchildren earlier.

Some critics say poor government organisation and public communication is responsible for the low pub-lic response to the swine flu vaccination programme.

It seemed health officials were illprepared to handle the fallout from people's adverse reactions to the vaccination.

In January, a cardiologist was confirmed with Guillain-Barre syndrome after having receiving a swine flu vaccination.

It was only after that that the Hospital Authority got its neurologists together to work out a protocol to deal with such incidents.

The government also failed to mobilise health care workers as advocates of the programme. Some doctors even advised patients not to take the shots.

By March 4, only 8.5 per cent, or 12,719 of Hong Kong's 150,000 health care workers had received swine flu shots. Only a third of public health care workers have annual flu vaccinations, and their response to swine flu vaccine has been much less.

University of Hong Kong microbi-ologist Ho Pak-leung said a winter flu peak was unlikely because of the strong immunity among elderly and young people.

'But obviously the government did a rather bad job in the vaccination programme,' Ho said. 'It did not put in adequate resources in the first place.'

For example, the government should have sent inoculation teams to schools when the programme began. 'The government responded too slowly to public concerns about adverse incidents so it failed to change public misconceptions,' he said.

Ho also criticised what he called poor co-ordination among different health authorities.

The Centre for Health Protection under the Department of Health monitors flu activity while the Hospital Authority oversees treatment.

Ho said the two did not co-ordi-nate well.

'The Centre for Health Protection does not get enough clinical data from the Hospital Authority, such as patient conditions and profiles, for in-depth analysis,' he said. 'Many countries have very detailed analysis of severe complications and fatal cases but this is lacking in Hong Kong. Doctors find it difficult to find useful information.'

A government experts panel repeatedly said the reported adverse incidents allegedly caused by vaccinations were not, in fact, caused by the shots. However, its statements had failed to restore confidence.

And in the absence of a major swine flu onslaught, many people decided that the benefits of vaccination were minimal.