Monday, 27 August 2012
Mandatory influenza immunization – a time that finally has come (or has it?)
So BC has made the leap into the unknown. In an announcement on August 23, BC is requiring health care workers to either be vaccinated, or where masks for the duration of the influenza season. BC media release
Sounds like rationale thinking, and ultimately something that will end up before the courts. While BC may be the first out of the starting block, it is not the only jurisdiction to have pondered the question, just the first to not shy away at the brink (yet).
There is no doubt that the highest risk clients for complications from immunization are found in health care settings. Residential care environments and collective living arrangements are prime settings for the spread of many germs, including influenza. Influenza vaccination is good, but not great – and its effectiveness is lowest in the very population that is at the highest risk.
So the alternate strategy of “cocooning” becomes important. Cocooning is somewhere between individual protection and herd immunity. Protect the herd, and those at risk are likely to achieve some level of protection – a phenomenon seen frequently with universal immunization programs. The few provinces with universal influenza immunization (Ontario in particular) may claim some benefit from universal programs, but only achieve coverage in half the population, a rate that is about 50% higher than provinces with targeted programming.
Cocooning provides a shell of protection around those at highest risk. Influenza vaccine, while beneficial at a personal level for all, highly recommended for those at any risk – is also recommended and often provided in Canada to those who live or work with those at highest risk. This later group is the “cocoon”. While the recommendation has been written for many years, uptake in this “cocoon” group is not great. Health care workers in particular have notoriously dismal uptake, often in the range of 40-50%. There are of course exceptions with some facilities doing very well, and others that clearly do not take seriously the threat of the illness.
Of course, there are competing sides in the debate. Most notably in favour would be the experts in infection control whose 2011 statement reaffirms the importance of health care worker immunization SHEA statement. On the flip side is the Cochrane reviews Cochrane summary and access point (written as first author by a University of Calgary internist) which typically of Cochrane, found limited controlled trial evidence of effectiveness of health care worker immunization.
The methodological challenge of course, is only a small fraction of health care facilities are affected by outbreaks during a year. A facility ultimately is a single event since the outcome of individuals in a facility is highly correlated – hence the study must recruit many facilities. Having said that, while no formal study is undertaken, someone should be able to pull together facility immunization rates and look at events in a case control approach over multiple years.