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ANTIVIRAL TREATMENTS FOR EXISTING INFECTION
AVIAN INFLUENZA
Two specific antiviral drugs are now available for the treatment of estab- Epidemics of influenza among poultry flocks in Asia have made headline lished influenza infection. Zanamivir (‘Relenza’) and oseltamivir (‘Tamiflu’) news, but the implications for human infection are still uncertain. Influenza both interfere with the access of influenza A and influenza B virus into cells A is fundamentally a virus of birds, with infection of humans and the and the escape of virus from cells. Zanamivir is administered as a twice establishment of distinct and self-perpetuating human strains an incidental daily inhalation to adults and children aged five years and over. Oseltamivir occurrence, according to Alan Hampson. Influenza A has 16 H (haemag- is administered as a twice daily capsule to those aged 13 years and over glutinin) types and nine N (neuraminidase) types. Only three H types (H1, and as a suspension formulation for children one year and older, and adult H2 and H3) and three N types (N1, N2, N8) have been known to occur as patients who cannot swallow capsules.
Dr Dominic Dwyer, medical virologist at Westmead Hospital in Sydney, Recent outbreaks originating in Asian countries have involved an H5N1 said the drugs are effective for laboratory-confirmed influenza infection, type, and human infections and deaths have been reported. “The concern reducing the severity and duration of infection.9,10 “Both treatments need is that the virus will adapt to the human host, either through mutation to be commenced within 36-48 hours of the first symptoms, and they or genetic reassortment by mixing with a human strain,” Mr Hampson are not effective against other viruses such as RSV, adenovirus, parain- said. “This type of antigenic shift is the basis of influenza pandemics.” A fluenza and metapneumovirus which can cause similar symptoms,” Dr vaccine seed virus has been produced by the UK. This is a Vietnamese Dwyer said. “We need to educate patients about the need to seek early strain of the H5N1. Trials testing this vaccine strain have commenced in treatment, rather than just spending the first few days at home in bed.” the USA and Australia will also trial vaccines using this same strain. A concern is that if the virus changes considerably in adapting to humans Most trials of zanamivir and oseltamivir have been in relatively healthy that this vaccine may no longer be immunogenic.
people. Effects in reducing the duration of illness are more pronounced in people with additional risk factors.
The ongoing spread of the Avian influenza into Mongolia and Russia continues to heighten the threat that a pandemic may result. WHO is PLANNING VACCINES FOR THE INFLUENZA SEASON
sponsoring the effort to prepare and coordinate an international response. The formulation of influenza vaccines for Australians is based on INFLUENZA SPECIALIST GROUP
information from an international surveil ance and monitoring program The Influenza Specialist Group consists of medical and scientific specialists A guide for occupational health professionals coordinated by the World Health Organization. Four Col aborating Centres for Influenza, in Atlanta, London, Melbourne and Tokyo, as well as professional and patient groups from around the country. It integrate information from 110 centres in 80 different countries. Mr Alan cooperates with state and federal governments in educational activi- Hampson, Convener of the ISG, said the network meets twice yearly ties about influenza. In conjunction with other organisations including Vaccination against influenza safely and effectively reduces
RISKS OF InFLUEnZA And
to make recommendations for vaccines for the fol owing Northern and the Australian Medical Association, Royal Australian College of General the risk of infection, and treatments are now available to
BEnEFITS OF VACCInATIOn
Practitioners, WHO Collaborating Centre for Reference and Research on Influenza, Pharmaceutical Society of Australia, National Asthma Council, al eviate the duration and severity of symptoms if infection
“Influenza is a ‘moving target’ for vaccines,” Mr Hampson said. Diabetes Australia and the National Heart Foundation it runs the annual occurs. Although Australia has made excel ent progress in
Influenza is a potentially fatal disease, and a number “Continuing antigenic drift, which is an evolutionary response by this Influenza Awareness Program. The Program, launched in 1992, informs targeting those aged 65 and older, the majority of younger
of studies have shown that deaths directly attributed easily-mutated RNA virus to host immunity, means that we have key audiences about the consequences of influenza and the importance of at-risk individuals - including many who are active in the
to the infection are a substantial under-estimate to make a prediction each year about the strains that wil be most workforce - remain unprotected. This publication, from
of the true mortality. A Dutch study, for example, the Influenza Specialist Group, reviews current issues in
estimated the mortality rate was four times higher Recommendations from WHO are taken to the Australian Influenza the prevention and treatment of influenza - at a time when
than that recorded in death certificates, with many Published by the Influenza Specialist Group deaths attributed to secondary cardiovascular Vaccine Committee, within the Therapeutic Goods Administration, in awareness of viral respiratory infections has been heightened and respiratory complications.1 An actuarial study
October each year for approval and implementation, allowing manufacture 21-31 Goodwood Street, Richmond VIC 3121 by the occurrence of SARS and the recent spread of avian
in Australia suggested the death rate could be of vaccines to commence. Vaccines normally contain two influenza A influenza, originating in South-East Asia, highlighting the
eight times higher than that officially recorded.2 In strains and one influenza B strain, and are developed from clearly-charac- threat of a potential worldwide pandemic.
addition, while people 65 years and older are at high terised laboratory stocks of the virus.
risk, nearly a quarter of all deaths occur in younger age groups (Table 1).
1. Sprenger MJW et al. Impact of influenza on mortality in relation to age and underlying disease, 1967-1989. International Journal of Epidemiology An Australian study estimated that influenza was responsible for a million medical consultations, 2. De Ravin JW, Gerrard PN. The ef ect of influenza on Australian mortality. Annual Transactions of the Australian Institute of Actuaries 1984; 471-479.
Australian vaccination rates: good progress but room for improvement 20,000-40,000 hospitalisations, 1,500 deaths and 3. Mil s, J. and Yapp, T. An economic evaluation of three CSIRO manufacturing research projects. 1996. Australia, CSIRO.
1.5 million days off work each year, and a total Health authorities support vaccination in chronic illness economic cost of about $600 million annually.3 4. Gross A et al. The efficacy of influenza vaccine in elderly persons. A meta-analysis and review of the literature. Annals of Internal Medicine 1995; 5. Nichol KL. Cost-benefit analysis of a strategy to vaccinate healthy working adults against influenza. Annals of Internal Medicine 2001; 161: 749-759.
Influenza vaccination is about 70% effective against 6. Cohen et al. J Occup Health Safety 19(2): 2003; 167-182.
Implementing a workplace influenza vaccination program laboratory-proven, symptomatic disease, according 7. Nichol KL et al. The ef ectiveness of vaccination against influenza in healthy, working adults. New England Journal of Medicine 1995; 333: 889-893.
to Dr Heath Kelly, Head of the Epidemiology Unit 8. Lee PY et al. Economic analysis of influenza vaccination and antiviral treatment for healthy working adults. Annals of Internal Medicine 2002; 137: Antiviral treatments for existing infection at the Victorian Infectious Diseases Reference Planning vaccines for the influenza season Laboratory. “There are special difficulties in 9. Hayden FG et al. Efficacy and safety of the neuraminidase inhibitor zanamivir in the treatment of influenza virus infections. GG167 Influenza Study Group. New England Journal of Medicine 1997; 337: 874-880.
assessing the effectiveness of influenza vaccination in ‘real world’ settings, and data from studies need 10. Hayden FG et al. Use of the oral neuraminidase inhibitor oseltamivir in experimental human influenza: Randomized control ed trials for prevention and treatment. JAMA 1999; 282: 1240-1246.
careful interpretation,” Dr Kelly said. Vaccinations against other viral infections such as measles are targeted at a stable virus, while the match between the vaccine Table 1: Estimated influenza deaths in the United Kingdom - 10 year period department visits or hospital admission, or requires treatment with high In one Australian company, vaccination benefits were calculated to be and circulating strains of influenza virus is not always perfect. In doses of inhaled corticosteroids or oral corticosteroids,” Ms Whorlow over two and a half times the cost of the program.6 This finding is also addition, only about 40% of ‘influenza-like’ respiratory viral infections, said. “There are a number of myths about influenza vaccination in people supported by international studies, with cost savings estimated at an characterised by rapid onset, fever and malaise, are in fact caused by with asthma. It does not trigger asthma attacks, although it may cause average of $US47 for every person vaccinated in a study published in a slight increase in symptoms in a minority of people. If this occurs, then it’s appropriate to increase the use of a preventer medication in line A number of analyses have addressed specific outcomes, and identified Table 2: Efficacy of influenza vaccination in preventing outcomes in elderly patients5 with the individual’s written asthma management plan. Most people, The benefit of workplace vaccination cannot be predicted each year, pronounced benefits in terms of proven influenza infection: Table 2 though, notice no difference in their asthma symptoms after influenza as it is influenced by the extent and virulence of the epidemic. A provides a representative example. In the frail elderly and those with recent review8 suggests employers need to make individual decisions underlying conditions, prevention of hospitalisation and death may be on whether to implement a workplace influenza vaccination based on the main aim, while in younger healthy people the focus may be on The National Heart Foundation also encourages people with a range decreasing time off work or reducing complications from pre-existing of cardiovascular diseases to have an annual influenza vaccination. “It’s been estimated that up to two-thirds of people hospitalised the ease of organising a vaccination program with influenza are younger than 65 and have conditions such as heart Contraindications to vaccination include hypersensitivity to the vaccine disease, lung disease or diabetes,” according to Dr Andrew Boyden, components and current febrile illness.
HEALTH AUTHORITIES SUPPORT
the Foundation’s Medical Affairs Manager. “Although this group suffers the potential impact of an epidemic.
a significant proportion of the total burden of the disease, only about AUSTRALIAn VACCInATIOn RATES:
VACCInATIOn In CHROnIC ILLnESS
40% of Australians aged between 40 and 65 who have such high-risk “In organisations where delivery of the vaccine is relatively easy and GOOd PROGRESS BUT ROOM FOR
Representatives of three leading health authorities have supported conditions are protected through immunisation.” An acute influenza sudden rises in absence would be catastrophic, the cost-benefit IMPROVEMEnT
the benefits of influenza vaccination in people with an underlying infection predisposed people with heart disease not just to a higher equation may favour vaccination,” the review stated. “Alternatively, chronic illness that increases their vulnerability to the infection and its risk of respiratory complications, but also risked exacerbating their where vaccine delivery is logistically difficult (for example, wide geographical spread, multiple bases) and the impact of an epidemic Dr Rosemary Lester, Manager of the Prevention and Perinatal Health on productivity would be less severe, the case for vaccination is not Section at the Department of Human Services in Victoria, said there has Greg Johnson, Chief Executive Officer of Diabetes Australia in Victoria, as strong.” In health and social care settings, the risk of transmission been good progress in vaccinating older Australians against influenza noted that NHMRC guidelines recommend vaccination for adults and from employees to clients, and vice versa, also needs to be taken into but room for significant improvement in protecting younger people children older than 6 months who have chronic illnesses that require regular medical follow-up. This includes diabetes. “We believe all “There is no vaccination register for influenza, but vaccination rates people with diabetes, regardless of their age, should be aware of this IMPLEMEnTInG A WORKPLACE
in Australians over 65s are fairly stable with latest research from the recommendation and discuss their individual needs with their doctors,” AIHW demonstrating uptake rates of 79% in this group,” Dr Lester said. Mr Johnson said. “Diabetes is a rapidly growing problem, affecting Only about 40% of
InFLUEnZA VACCInATIOn PROGRAM
Australians of al ages. Influenza can exacerbate the problems of Australians aged
The NHMRC recommends vaccination in adults and children older than 6 diabetes, and it is sensible to take steps to avoid it.” Influenza vaccination programs have been implemented successfully in months with chronic pulmonary or circulatory disease, including severe workplaces for many years, according to Dr Brandon Carp, managing between 40 and 65
asthma, and other chronic illness that required regular medical follow-up The NHMRC also recommends vaccination for people with severe director of the Unified Healthcare Group. “Each program should be who have such high-
or hospitalisation in the preceding year. In these at risk groups, latest asthma. Kristine Whorlow, Chief Executive Officer of the National individualised, with the promotion to staff, the arrangements for funding research has shown that only 42% of people are getting vaccinated Asthma Council, said the effects of influenza and the risks of and other issues being determined according to the circumstances,” he risk conditions are
complications could be more problematic in the presence of underlying said. “The programs are very well received because staff and employers asthma and other chronic respiratory illnesses. “We define ‘severe’ protected through
both benefit from protecting employees’ health, reducing the risks of “Influenza vaccination is a proven lifesaver for older people and those at asthma as asthma which causes persistent or frequent symptoms transmission in the workplace, and decreasing the time lost from work.” immunisation.
risk for other reasons,” Dr Lester said.
including night-time asthma, limits physical activity, needs emergency Employers considering an influenza prevention program should assess it like other investments, accounting for the potential direct savings of reduced sick leave and lost productivity, as well as the indirect IS IT InFLUEnZA?
WORKPLACE VACCInATIOn
advantages of offering a staff benefit.
Influenza vaccination programs now tend to be undertaken by Some people call any cold or other upper respiratory tract infection ‘the flu’. It’s important to realise that influenza is a specific illness caused by the Vaccinating healthy working adults against influenza will generate cost contractors rather than in-house personnel. Consultants are able to influenza virus. Some of the features of influenza are listed in Table 3.
savings 95% of the time.5 The exact economic outcomes may vary assist with promotion of the program, education about the health from year to year, depending on factors such as the illness rate in each consequences of influenza and information about the efficacy and safety season, the absenteeism that results, and the hourly rate of pay of of vaccination. “It is vital that a flu vaccination program is provided through a professional and comprehensive service using well-trained professionals, that the quality of the vaccines is preserved by following It has also been demonstrated that vaccination has benefits beyond strict ‘cold chain’ measures, and that any adverse reactions can be dealt protecting employees against influenza. A study in healthy employees aged between 18 and 64 found those who were vaccinated against Workplace vaccination is an excellent method for protecting younger Chills, muscle aches, malaise, cough, sore people with underlying chronic diseases against influenza. “A large 25% fewer episodes of upper respiratory tract illness proportion of this age group are in the workforce but mightn’t 43% fewer days off work because of upper respiratory illness necessarily have the opportunity to discuss it with their GP,” Dr Carp said. “They often view themselves as healthy, and might not be aware *Note: some other respiratory viruses may cause influenza-like illness 44% fewer visits to doctors because of upper respiratory illness.
of the special advantages of vaccination.”

Source: http://www.isg.org.au/assets/assets/FINAL-revised-OH-discussion-paper-2005-.pdf