Introduction

In spring 2009, the World Health Organisation declared the first worldwide pandemic influenza (flu) outbreak for over 40 years. Last year’s Public Health Annual Report described the public health response to this outbreak.

We identified the need for high quality research into the impact of 2009 Influenza A(H1N1) (swine flu). Accordingly we established a partnership between NHS Lothian (Public Health and Health Policy and Maternity Services), the University of Edinburgh (Obstetrics and Statistics), the Regional Virology Laboratory in Glasgow and the Wellcome Trust’s Clinical Research Facility. The aims of the PIPPIN study (Prevalence of Influenza A(H1N1) in Professionals and Pregnant women in NHS Lothian) were to investigate the levels of immunity to A(H1N1) in healthcare workers [Phase 1] and the effects of A(H1N1) on pregnant women [Phase 2].

Phase 1 – Healthcare workers

During the A(H1N1) pandemic, there was anxiety that high numbers of healthcare staff might be affected by A(H1N1), particularly as many would come into direct contact with symptomatic patients. In September 2009 our team saw an opportunity to undertake research into A(H1N1) in NHS Lothian. We set out to identify what proportion of healthcare workers in NHS Lothian naturally possessed antibodies to A(H1N1) at two time points – before and midway through the pandemic. The study needed to recruit unvaccinated healthcare workers, because vaccinated people would exhibit antibodies that would be indistinguishable from naturally acquired antibodies. Given the importance of improving understanding of the A(H1N1) pandemic, the Wellcome Trust Clinical Research Facility agreed to reprioritise their work to support the PIPPIN study.

Recruitment into Phase 1 took place over a five day period starting on 28th October 2009. Volunteers completed a short questionnaire (including details on age, gender, occupation and history of flu-like symptoms since spring 2009) and gave an anonymous sample of venous blood. In total, 493 NHS Lothian healthcare workers were recruited into the study. The study participants closely matched the age, sex and occupation distributions of staff in NHS Lothian. The Virology Laboratory in NHS Lothian also identified 471 anonymous age and sex matched samples stored from healthcare workers from the months prior to the start of the A(H1N1) pandemic. All samples were forwarded to the Regional Virology Laboratory in Glasgow. The Glasgow Laboratory liaised with the Health Protection Agency Centre for Infections in Colindale (London) to develop the necessary assays. The Glasgow Laboratory performed all of the virology testing for the PIPPIN study.

Preliminary analyses have shown that 6.6% of healthcare workers tested prior to the A(H1N1) pandemic showed antibodies to A(H1N1). These healthcare workers are likely to have been exposed previously to flu strains that caused their immune system to produce antibodies similar to those raised against A(H1N1). For those healthcare workers tested during the pandemic, 10.3% had antibodies to A(H1N1). While this represents an increase in immunity levels during the pandemic it suggests that only one in ten healthcare workers had antibodies to A(H1N1) by November 2009. This was despite the fact that almost one in two study participants recalled having had flu-like symptoms since A(H1N1) had been identified in Scotland. More detailed analyses from Phase 1 were undertaken in 2010 and will be more widely available in 2011.

Phase 2 – Pregnant women

Scientific reports from the early days of the A(H1N1) pandemic, and high profile cases in the media, appeared to suggest that pregnant women were at increased risk of catching A(H1N1) and developing complications. In order to investigate this further we recruited over 400 pregnant women who agreed to give a blood sample and complete a questionnaire between December 2009 and April 2010. The information gathered is now being analysed and research findings will be published shortly, with preliminary findings showing that A(H1N1) infection was relatively uncommon in pregnant women and serious complications were rare.

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