Guest Post: Thinking about Contact Precautions

Anthony Harris, MD MPH
This is a guest post from Dr. Anthony Harris, Professor of Epidemiology and Public Health, University of Maryland School of Medicine.

I have a lot of admiration for this blog and in the spirit of academics, I would like to share my somewhat different interpretation of the contact precautions literature. I offer three points for your consideration:
1. Contact precautions do not lead to an increase in adverse events: 

Instead of the frequently cited small observational studies, I think it is most important to focus on the one randomized trial that evaluated adverse events associated with contact precautions (I acknowledge my bias in that it is the study I led). A randomized trial should most often trump observational studies especially since it's near impossible to control for confounding by indication, i.e. why was the patient placed on contact precautions. In fact, the latest analysis of our randomized trial data showed a trend towards decreased adverse events in the universal contact precaution arm. (See: Croft L et al. Clin Infect Dis. 2015 Aug 15;61(4):545-53). To quote from the Conclusion: "Concerns of adverse events resulting from universal glove and gown use were not supported." So we should be clear that other than the cost issues of gloves and gowns no high level study has shown any adverse events from contact precautions. Healthcare workers do go into the patient room less often when the patient is on contact precautions but this has not been shown to lead to an increase in adverse events. In my experience (and the data supports this), healthcare workers just bundle their activities and thus perform the same activities in the room with fewer visits.

2. Methodological problems in studies that have removed contact precautions: 

Studies that show no effect of removing contact precautions have serious methodological problems. The largest problem is that they are incredibly under-powered. The studies that show “no difference when you remove contact precautions” are too small to detect a difference and thus may falsely conclude that removing contact precautions is safe.

3. Need a better solution before removing the current standard of contact precautions: 

As much as I would love to stop wearing gloves and gowns, antibiotic-resistant bacteria are a continuing problem. They are not going away and other than MRSA, they are not decreasing. Until we have better solutions, I believe that we should not be abandoning contact precautions. This is particularly true in high risk settings such as the ICU. In the ICU where acquisition of an MDRO leads to infection 20-30% of the time during the index ICU admission, the stakes are too high not to prevent patient-to-patient transmission. I believe that the phase 0, phase 1 and phase 2 data on contact precautions are strong and the biologic plausibility that they prevent patient-to-patient transmission so strong that I don’t think we should abandon contact precautions based on underpowered "removal studies" and an adverse-event literature with few studies with strong internal validity. Of course there are certain settings and certain bacteria where removing contact precautions might make sense and these scenarios should be studied using large, sufficiently powered and methodologically sound trials.


  1. Hi Anthony,

    Excellent post, thanks for supporting the blog—your group has done great work in this area. My quick 2 cents:

    I am concerned that this debate has become too polarized (like our politics, except not as stupid). We shouldn’t be asking, “Can we get rid of contact precautions (CP)?” We should be asking, “How can we apply CP most effectively?” I don't know of many people who don’t think CP can be one of several valuable interventions during outbreaks, for example, or for particular organisms while awaiting better evidence about their epidemiology.

    The contested hypothesis seems to be: “CP reduces MRSA and/or VRE transmission in the endemic (non-outbreak) setting”. As you point out, randomized trials should be preferred over small observational studies to answer this question. In my review of the available cluster-randomized trials (STAR*ICU, BUGG, REDUCE-MRSA, and MOSAR), the preponderance of the data suggests that expansion of CP is not associated with a reduction in MRSA and/or VRE acquisition events or infections. So although the association, or lack thereof, between CP and adverse events is of interest, it doesn't enter into my thinking about whether to routinely apply CP to the MRSA or VRE colonized patients in the absence of an outbreak. But you heard my talk on this at IDWeek, so you know how I feel about it.

    Regarding the underpowered observational nature of single center experience with changing CP policy, I fully support the funding of “large, sufficiently powered” trials of competing approaches to endemic MRSA and VRE control. However, in the absence of convincing data from large, sufficiently powered studies that CP actually works for MRSA and VRE control, I’m not sure why the default should be CP. Obligating hospitals to adopt CP routinely for MRSA and VRE should also be supported by data from such trials, no? And until such data are available, hospitals should be free to adjust their approaches so long as they carefully track relevant outcomes.

    As an aside, a logical extension of the power argument would lead to the conclusion that no hospital anywhere could ever stop anything, since the power of any before-after analysis they did would not be sufficient to conclude that it was safe. This does not bode well for my belief that singing Broadway show tunes on rounds can reduce MRSA transmission.

    Thanks again, Anthony, and thanks also for the contributions your group has made to our knowledge base about CP.



  2. Fascinating post Dr Harris - thanks. Enjoyed it.

    One comment on point #1. Adverse events were not significantly higher in the universal glove and gowning arm, which seems to suggest that other studies were wrong and patients on contact precautions are not at a higher risk of adverse events. However, could it be that the reason why adverse events are more common for patients on contact precautions is that they are marginalized by being on contact precautions so get less attention from healthcare workers? If all patients are effectively on contact precautions, the time of healthcare workers would be spread evenly.

    So, I think the cluster RCT to explore adverse events and contact precautions would have to be a mixture of patients on contact precautions vs. all patients on contact precautions vs. no patients on contact precautions!

    1. Interesting idea Jon. There is some evidence of the marginalization hypothesis in our observational studies. Anthony highlighted one of our studies which showed reduced frequency of visits per hour. However. the clinicians made up for most of their lack of attention by bundling care into their less frequent visits. This resulted in the average HCW-patient visit increasing from 4 under standard precautions to 5 minutes under contact precautions. It's possible that you could do the study as described, but who would put up the 7 million GBP and how would the design deal with the flaws Anthony has highlighted?

      The larger criticism, which Anthony highlighted and would surely exist in your proposed study, is that any study where contact precautions were linked to colonization status, eg MRSA colonization/infection, would necessarily result in confounding by indication. The MRSA+ patients would be necessarily older and sicker and more likely to fall, feel depressed and suffer adverse events independent of their contact precaution status.

      To sum up these points, you would have to do an individual randomized trial where you randomize patients to contact precautions independent of colonization/infection status and this study would cost several million GBP and even more USD and it's unclear who would pay for such a study or if isolating patients at random would be ethical. - See more at:


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