The level of staff absence from work during a pandemic will depend significantly on the nature of the pandemic virus when it emerges. The planning assumptions set out below are based on current knowledge, analysis of past pandemics, published evidence and scientific modelling. Given the inevitable uncertainties, a range of figures is given in some areas. Organisations should ensure that their business continuity plans have the flexibility to accommodate these ranges.

During a pandemic, staff will be absent from work if:

They are ill with flu . Numbers in this category will depend on the clinical attack rate. If the attack rate is 25%, a quarter of staff in total will be sick (and hence absent from work for a period) over the whole course of the pandemic. If a pandemic occurs over one wave, this level of cumulative absence could be experienced by employers over a period of around 3-4 months. But there may well be more than one wave, with absence from work being spread across those waves.

• They need to care for children or other family members who are ill with flu.
• They have non-flu medical problems.
• Their employers have advised them to work from home.
• They decide to absent themselves for other reasons.
• They need to care for children who are unable to go to school because of closures.

Business continuity planning against an influenza pandemic should have at its heart an estimate, through aggregation of data in each of the categories above, of the number of staff likely to be absent from work at the peak of the pandemic. Estimates of likely levels of absence from work caused by influenza or by the need to care for family members with influenza (that is, categories a) and b). above) are set out in the table below against a range of assumptions on the clinical attack rate of the pandemic virus. The table also reflects the results of scientific modelling which suggests that small organisations, and small teams within larger organisations, may experience higher rates of staff absence at the peak of a pandemic than would large teams.

Clinical attack rate of influenza

Attack rate	10%	25%	50%
Large Organisation	2%	5%	10%
% of people ill at peak
% of people ill and carers taking time off at peak	3%	7%	15%
Small organisation % of people ill and carers taking time off at peak	6%	14%	30%
Total Cumulative % total of those ill over whole period of pandemic	10%	25%	50%

These figures are estimates based on current knowledge and modelling

• All figures given are percentage of total workforce
• It is expected that ill people will on average be absent for 5-8 working days
• A small organisation or unit can be defined as a group of up to 15 people
• These figures do not include 'normal' absenteeism levels; people taking time off due to family bereavement or psychosocial impact of pandemic; people self-absenting from work .

In order to derive estimates for the total number of staff likely to be absent from work at the peak of a pandemic, employers should add data appropriate to their circumstances on:

• The average number of staff 'normally' absent from work.
  
• The proportion of staff whom they will advise to work from home.
  
• Their judgement, based on the nature of their business and their employment practices, of the number of staff who might absent themselves from work for other reasons.

As a rough working guide, organisations employing large numbers of people, with flexibility of staff redeployment, should ensure that their plans are capable of handling staff absence rates of up to 15% over the 2-3 week peak of a pandemic (in addition to usual absenteeism levels). Small businesses, or larger organisations with small critical teams, should plan for level of absence rising to 30% at peak, perhaps higher for very small businesses with only a handful of employees.

Finally, employers should note that:

• Depending on the rate of spread of the virus within the UK , levels of staff absence from work are unlikely to be uniform across the country. Employers with sites spread across the UK may experience peak rates of absence at different times in different regions.
• Absentee rates could be higher than the estimates given here if the nature of the virus means that people take longer to recover from infection than the assumption shown above, or if some age groups of the population are affected more severely than others.