Essentially there are three different methods for taking antivirals to mitigate the effects of pandemic influenza
For when the employee takes a preventive antiviral course for a specified period. Currently Tamiflu is licensed for six weeks continuous use [4+ OP]
Antiviral medication is only licensed for six
weeks continuous therapy. Evidence from epidemic
flu suggests continuous preventive therapy is very
effective, reducing the incidence of influenza
by up to 90% in epidemic influenza outbreaks which
normally last around six weeks
The main problem with this method for pandemic
as opposed to seasonal influenza however is timing.
Evidence suggests that the first wave of a pandemic
in UK will last 15 weeks or longer, probably in
an overlapping spread of local epidemics [~six
week long], from centres of high population density
to more remote rural areas. Different areas of
UK will probably therefore be at different alert
phases during a pandemic. This is currently the
situation in UK with Scotland at a more advanced
stage than any of the English regions.
If the preventive courses are started as soon
as local cases are reported [Alert phase 6.3 or
6.4] this should offer significant protection,
and a high proportion of those exposed to the pandemic
virus will also develop protective antibodies to
further infection by the same virus.
If however the courses are started as soon as
a pandemic is declared [at alert level 6.1 or 6.2]
there is a significant risk of completing the courses
before local outbreaks occur, and consequently
being exposed and vulnerable to the virus when
the virus is circulating locally
Conclusions:
- Very effective at reducing infection rates by up to 90% but timing is critical
- Significant risk of leaving population vulnerable at peak time
For when the employee takes a treatment course
as soon as influenza like symptoms develop.
Effective method for reducing symptoms, complications, and duration of illness, by up to 60%. Effectiveness depends on starting the antiviral course as soon as symptoms develop.
If taken up to 36 hours after symptoms develop reduces duration of illness by around one day. If taken within six hours of symptoms reduces duration of illness by up to four days.
No reduction in number of employees contracting pandemic influenza but reduces number of days lost to sickness absence, and should reduce complications, morbidity and mortality.
Little effect on reduction of absences due to
family illness particularly children. Current UK
Department of Health main Strategy when 6.3 is
reached at which stage containment is no longer
possible and further spread inevitable. This is
the strategy currently being applied in UK hotspots
e.g. West Midlands
Conclusions:
- Lasting protective immunity to pandemic virus unless major antigenic shift
- Simple and relatively inexpensive to run regime
- Risk of inappropriate use for non pandemic Influenza Like illness [ILI] particularly if pandemic occurs during “normal” winter flu season, leaving employee vulnerable to exposure to pandemic virus. Less likely at present during summer as ILI more likely to be Pandemic virus
- IPL advice is to take antiviral as soon as symptoms develop without diagnostic confirmation
For when the person takes a preventive course
of antiviral when in contact with a known or suspected
case of influenza. This can be either a household
contact [Household PEP] or in an occupational or
other setting [Targeted PEP]
Very effective at preventing illness in contacts of symptomatic cases. In family setting, significantly reduces spread of illness in families in particular children, and will, at least initially, have a significant impact on reducing spread of the disease in the community.
An added bonus is that persons exposed to the
pandemic virus and taking PEP, will in a significant
proportion of cases [up to 80%] develop immunity
to further infection with the same virus. Currently
this is the UK Department of Health’s initial strategy
to reduce the initial spread of the disease, but
only as far as their limited antiviral stocks allow.
This has so far been very effective in slowing
and containing spread of the virus
Similar to above but person advised to take antiviral when in close contact with symptomatic case either at home or in the workplace. Significant risk of employee taking PEP for non pandemic ILI.
By providing the employee with two PEP courses, however, this risk is reduced. It is anticipated that a significant number of employees [up to 80%] taking PEP who have been exposed to the pandemic virus will develop immunity without developing symptomatic illness.
The addition of a treatment course for each employee will ensure that those who do develop symptomatic illness will at any time be able to mitigate this effectively by starting the treatment course as soon as symptoms develop.
IPL recommend 2 PEP and 1 Treatment course as
being the most clinical and cost effective, regime
based on current evidence and modeling.
Conclusions:
- PEP is proving to be highly effective at reducing spread of disease, and will provide significant levels of protection immediately and, in a high proportion of cases, long lasting immunity
- PEP already well tried in clinical Occupational Health medicine setting to deal with exposure to blood borne viruses
- Risk of inappropriate therapy during a pandemic due to self diagnosis of significant contact by non medical personnel. During an established pandemic it is estimated that 90% of cases of Influenza like illness [ILI] will be pandemic flu
- Provision of a second PEP course and a treatment course to be taken if symptomatic flu develops mitigate the above concerns, and make this potentially a very useful method at reducing infection rates, mitigating against complications and providing a significant level of immunity in participants without symptomatic clinical disease