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This large trial looked at the impact of online advice to the public about effective handwashing. It found that using soap and water or hand gel reduced the number of cases of colds and flu, the severity of symptoms, the length of time people were ill and the spread of infection within households.

Colds and flu cost the UK economy through sick leave and treatment costs, as well as causing deaths. Effective public health measures to prevent colds and flu and reduce their spread could decrease costs, sickness and deaths.

The Medical Research Council funded this trial to provide large-scale, high quality evidence about the effectiveness of handwashing to prevent and reduce the spread of colds and flu.

Why was this study needed?

Respiratory tract infections such as colds and flu affect the sinuses, throat, airways or lungs. Seasonal outbreaks of flu and other respiratory tract infections contribute to higher death rates during winter, as well as costing the UK economy through people requiring treatment and sick leave.

Public Health England’s annual campaign to raise public awareness about reducing the spread of infection, encourages people to cover their mouths when coughing and sneezing, ideally using a tissue to “Catch it, kill it, bin it”.

There is evidence to show that regular handwashing (with alcohol hand gel or soap and water) is also effective at preventing the spread of infections in healthcare settings. However, there was no high quality evidence about handwashing in the community.

Therefore, the Medical Research Council funded this randomised controlled trial to provide high quality evidence for its recommendations and advice.

What did this study do?

The PRIMIT trial recruited 20,066 people aged over 18 years to participate over three winters in 2011, 2012 and 2013, non-pandemic years. Invitations were sent by post, to people randomly selected from 344 GP surgeries.

Those who agreed to take part were randomised to either have access to a website providing handwashing advice or not (the control group).

Before being allocated to the intervention or control group, participants were randomised to either receive an initial questionnaire about their handwashing habits or not. This step was introduced part-way through the trial as there was a concern that the questionnaire might be leading people to change their habits even if they didn’t access the handwashing site.

Participants could choose to wash their hands using soap and water, or alcohol hand gel – which they could collect free of charge from their GP surgery.

What did it find?

  • Fewer people in the handwashing group had one or more episodes of a respiratory tract infection (51%) than those in the control group (59%) after 16 weeks (multivariate risk ratio 0.86, 95% confidence interval 0.83 to 0.89). There were also 1% fewer cases of a flu-like illness and 4% fewer gastrointestinal infections amongst those in the handwashing group and fewer illnesses in household members within a week of someone else in the house becoming ill.
  • For those who developed an infection, the symptoms were less severe and the illness lasted for a shorter amount of time amongst the handwashing group (9.8 vs 10.6 days).
  • Transmission of infection was reduced in the handwashing group, with fewer cases of the participant getting ill within a week of another household member (7.8% vs 9.0%) or another householder getting ill within a week of the participant (6.8% vs 8.8%).
  • There were fewer antibiotic prescriptions amongst people in the handwashing group at 16 weeks (5.6% vs 6.4%) and at one year (9.3% vs 10.5%). There were also fewer GP visits or hospitalisations in the handwashing group at 16 weeks (10.0% vs 10.7%) and at one year (16.0% vs 17.3%).
  • Most participants completed at least part of all four of the online sessions (mean 2.9 sessions).

What does current guidance say on this issue?

Public Health England’s 2015 guidance recommends “careful and frequent” hand washing to minimise the spread of colds and flu in healthcare settings. They say that influenza viruses can be transferred to hands from materials such as magazines and clothing for up to two hours and from glass or plastic up to 24 hours after contamination.

Public Health England recommends using The World Health Organization’s guide on when to wash hands and how to do so effectively. The NHS also recommends that people can reduce the risk of catching or spreading colds and flu by practising good hygiene such as hand washing and sneezing into tissues.

What are the implications?

Hand washing is a low-cost, easy to implement, yet effective infection control measure that could potentially save money for the UK economy by reducing healthcare costs and sick leave. However, the authors of this trial do not provide information about the cost of producing the online materials, costs involved in website maintenance or the cost of supplying hand gel.

The handwashing resources could be produced nationally and shared locally to reduce costs, but this would be dependent on local IT infrastructure. The Office for National Statistics estimates that 84% of households have access to the internet. However, it is important to consider those who do not have internet access and therefore may not be able to use the website.


Little P, Stuart B, Hobbs FD, et al. An internet-delivered handwashing intervention to modify influenza-like illness and respiratory infection transmission (PRIMIT): a primary care randomised trial. Lancet. 2015;386(1004):1631-1639.

Funded by Medical Research Council and managed by National Institute for Health Research on behalf of the MRC-NIHR partnership.



NHS Choices. Flu - prevention. London: Department of Health; 2015.

PHE. Infection control precautions to minimise transmission of acute respiratory tract infections in healthcare settings. London: Public Health England; 2015.

WHO. How to handwash. Geneva: World Health Organization; 2006.

WHO. Your 5 moments for hand hygiene. Geneva: World Health Organization; 2006.

Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre


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The World Health Organization recommends that hands are washed when visibly dirty, but otherwise antiseptic hand gel should be used. World Health Organization guidance states that the most effective technique consists of wetting hands first, using enough soap to cover all of the hands, working soap into all the crevices of the hands by rubbing hands together using various motions, rinsing hands thoroughly with water, drying hands using a single paper towel and finally using the towel to turn off the tap.



Expert commentary

This study finally provides the evidence that hand hygiene in the home setting is an effective means of reducing the rate of respiratory tract infection – something that up until now only common sense supported. The added benefit of a reduction in GP consultations and antibiotic prescriptions makes the data from this study highly relevant to winter preparedness in primary care and should inform public information campaigns in future.

Carole Fry, Department of Health Nursing Lead on Infectious Disease.

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