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ECDC: Effectiveness Of Chemo-Prophylaxis During The Pandemic

 

 


# 4853

 

 

During the opening months of the pandemic there were widely varying policies and opinions around the world as to how antivirals would be used. 

 

In the UK, fearing that patient loads would overwhelm their medical system, just about anyone who exhibited flu-like symptoms could call a hotline and get a packet of Tamiflu prescribed without testing or seeing a doctor.

 

In the United States, and many other countries, antivirals were used more conservatively, partially out of concerns over fostering antiviral resistance.

 

Now that the pandemic is over, we are getting studies looking at how these varying strategies worked.  

 

Today the ECDC’s web portal has summaries, and a comparison, of two recent journal articles that looked at the therapeutic and prophylactic use of antivirals during the pandemic.

 

Differing effectiveness of the therapeutic and prophylactic use of antivirals and other measures for public health purposes during the 2009 influenza A(H1N1) pandemic

31 Aug 2010

 

 

The two studies in question are:

Lee VJ, Yap J, Cook AR, et al.
Oseltamivir Ring Prophylaxis for Containment of 2009 H1N1 Influenza Outbreaks
New England Journal of Medicine; Volume 362:2166-2174; 10 June 2010; Number 23

and

Health Protection Agency UK The role of the Health Protection Agency in the ‘containment’ phase during the first wave of pandemic influenza in England in 2009
Health Protection Agency, March 2010

 

At first glance, these two studies appear to come up with different conclusions. 

 

In the first study, which I profiled back in June (see CIDRAP On Two NEJM Pandemic H1N1 Studies), ring prophylaxis (or PEP) was shown to slow down or contain an influenza outbreak in a closed or semi-closed setting.

 

The second study, conducted by the UK’s HPA, found that chemo-prophylaxis could be effective in the home, and somewhat effective in schools, but proved less effective when scaled up to a larger community.

 

The ECDC’s comment (slightly reformatted for readabilty) follows:

 

ECDC Comment (19/08/10)


On the surface these two evaluations suggest different outcomes while in reality they are compatible.

 

Both found that if antivirals are used intensively in small defined populations in combination with personal health measures even pandemic influenza can be halted at least for a while. That is consistent with other observations of the effectiveness of oseltamivir against the pandemic strain.(1)

 

However when scaling up to the macro-level such containment is simply impossible as well as being very resource intensive and exhausting.  That is what was suggested by WHO in April and the UK experience was reported to the Swedish Presidency meetings in July 2009 which led to the abandonment of containment policies in Europe.(2,3)

 

It had been pointed out in the UK by their official evaluation that containment was never part of the original plan.(4)

 

Whether or not to use antivirals in a pandemic remains a controversial area. In some EU countries it was policy to offer them to all people when they developed symptoms, in others only to those at higher risk of severe disease and in yet others to confine their use to those ill enough to require hospital treatment.

 

Dilemmas for clinicians were that it is generally agreed that to be effective antivirals had to be given early, hence waiting for someone to become very ill was risky. Equally the policy of giving treatment to only those in the risk group was confronted with the fact that around 30% of those who eventually died from the pandemic infection were outside any risk group.(5) 

 

 

Of course, limiting the spread of the virus isn’t the only measure of the effectiveness of chemoprophylaxis. 

 

The aggressive use of antivirals in some communities may have reduced pandemic morbidity or mortality, but without a uniform surveillance and reporting system (and definition of `flu-related fatality’), it is exceedingly difficult to judge.

 

No doubt, some group of researchers is working on that weighty problem, and in time we may have a better idea of how antiviral use affected these numbers.

 

The pandemic of 2009 will no doubt end up being the most studied pandemic in history (up to now). 

 

Over time we should end up with a better understanding of what mitigation strategies worked best under which circumstances.

 

It is unlikely, however, that we will find a `one-size-fits-all’ solution.

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Antiviral
Pandemic

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