Influenza in working populations: an overview.

Abstract

The approach to managing influenza in working populations remains a topic that provokes vigorous debate. The assumption that there is a major deleterious effect on productivity and attendance has been questioned [1], as has the efficacy and cost benefit of immunization programmes. The UK is perhaps more sceptical than other nations about the worth of annual immunization programmes. In particular, the recommendation to immunize health care workers (which has been advocated for many years by the US Advisory Committee on Immunization Practices [2]) has not been endorsed by the UK Joint Committee on Vaccination and Immunization. For the average workforce (excepting health and social care), the issue is of sickness absence prevention and maintenance of productivity. Within health and social care settings, another significant problem is the transmission of infection from carer to client, with potential serious consequences. Influenza remains a major cause of disease and death. The populations most affected are the young, the elderly and those with chronic disease. There seems little indication of increased susceptibility dependent on occupation (for instance, there is no evidence of increased incidence in health care), though avian influenza has been associated with poultry handling in Asia [3]. It is difficult to quantify the precise impact on a workforce of influenza epidemics. Anecdotes are legion, as are economic estimates, but it remains difficult to determine the absolute contribution of influenza to sickness absence in the winter. The other winter viruses, whose peak incidence is often coincident to influenza, may cause influenza-like illness (ILI). True incidence rates of infection are rarely obtained, most epidemiology relying on proxy measures based on consultations in primary care with ILI or relative increases in virology laboratories’ detection rates. However, it is probable that infection (confirmed by serological change) occurs in ~20% of the adult population most years—obviously dependent on the scale of the epidemic [4]. Infection does not necessarily mean clinical disease, however. There may be a spectrum of clinical manifestation of infection, ranging from asymptomatic to the classic prostrate, feverish patient confined to bed. Again, therefore, knowing whether vaccination has been effective in preventing clinical influenza is an uncertain business. It is possible that workplace absence due to other winter viruses may equal or exceed that caused by influenza. Yet influenza is different; it tends to occur in observable epidemics, potentially causing catastrophic sudden increases in absence, with the consequent severe short-term effects on a business. There are also vaccines and drugs that could prevent or attenuate the effects of the epidemic. No effective vaccine exists yet for the common cold, but inactivated influenza vaccine has been in use for decades. Significantly, newer antiviral agents are also now available, introducing the possibility of drug prophylaxis and early treatment. At present, their role may be limited, possibly only to institutional use during a severe epidemic or in an outbreak situation. However, the development of near patient testing technology may in future open up the possibility of early diagnosis and intervention—some of which might be appropriate for a workplace setting where rapid access to an occupational health service is practicable. In the following reviews, we cover the epidemiology of influenza and the key issues relevant to workplaces. Stephenson and Zambon review the epidemiological and virological background, with a timely reminder about the prospect of the next pandemic. Fleming gives an update on antiviral drugs, while Jefferson et al. review the currently available vaccines. The paper by Stott et al. reprises the evidence for nosocomial transmission in health and social care settings. Finally, O’Reilly and Stevens review sickness absence due to influenza. What conclusions can we draw? Readers who are hoping for straightforward guidance on whether or not they should advise employers to offer vaccination may be dismayed to find no simple answer. The evidence for